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rfc:rfc5810

Internet Engineering Task Force (IETF) A. Doria, Ed. Request for Comments: 5810 Lulea University of Technology Category: Standards Track J. Hadi Salim, Ed. ISSN: 2070-1721 Znyx

                                                          R. Haas, Ed.
                                                                   IBM
                                                      H. Khosravi, Ed.
                                                                 Intel
                                                          W. Wang, Ed.
                                                               L. Dong
                                         Zhejiang Gongshang University
                                                              R. Gopal
                                                                 Nokia
                                                            J. Halpern
                                                            March 2010
         Forwarding and Control Element Separation (ForCES)
                       Protocol Specification

Abstract

 This document specifies the Forwarding and Control Element Separation
 (ForCES) protocol.  The ForCES protocol is used for communications
 between Control Elements(CEs) and Forwarding Elements (FEs) in a
 ForCES Network Element (ForCES NE).  This specification is intended
 to meet the ForCES protocol requirements defined in RFC 3654.
 Besides the ForCES protocol, this specification also defines the
 requirements for the Transport Mapping Layer (TML).

Status of This Memo

 This is an Internet Standards Track document.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Further information on
 Internet Standards is available in Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc5810.

Doria, et al. Standards Track [Page 1] RFC 5810 ForCES March 2010

Copyright Notice

 Copyright (c) 2010 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents
 (http://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.

Doria, et al. Standards Track [Page 2] RFC 5810 ForCES March 2010

Table of Contents

 1. Introduction ....................................................5
 2. Terminology and Conventions .....................................6
    2.1. Requirements Language ......................................6
    2.2. Other Notation .............................................6
    2.3. Integers ...................................................6
 3. Definitions .....................................................6
 4. Overview .......................................................10
    4.1. Protocol Framework ........................................11
         4.1.1. The PL .............................................13
         4.1.2. The TML ............................................14
         4.1.3. The FEM/CEM Interface ..............................14
    4.2. ForCES Protocol Phases ....................................15
         4.2.1. Pre-association ....................................16
         4.2.2. Post-association ...................................18
    4.3. Protocol Mechanisms .......................................19
         4.3.1. Transactions, Atomicity, Execution, and Responses ..19
         4.3.2. Scalability ........................................25
         4.3.3. Heartbeat Mechanism ................................26
         4.3.4. FE Object and FE Protocol LFBs .....................27
    4.4. Protocol Scenarios ........................................27
         4.4.1. Association Setup State ............................27
         4.4.2. Association Established State or Steady State ......29
 5. TML Requirements ...............................................31
    5.1. TML Parameterization ......................................34
 6. Message Encapsulation ..........................................35
    6.1. Common Header .............................................35
    6.2. Type Length Value (TLV) Structuring .......................40
         6.2.1. Nested TLVs ........................................41
         6.2.2. Scope of the T in TLV ..............................41
    6.3. ILV .......................................................41
    6.4. Important Protocol Encapsulations .........................42
         6.4.1. Paths ..............................................42
         6.4.2. Keys ...............................................42
         6.4.3. DATA TLVs ..........................................43
         6.4.4. Addressing LFB Entities ............................43
 7. Protocol Construction ..........................................44
    7.1. Discussion on Encoding ....................................48
         7.1.1. Data Packing Rules .................................48
         7.1.2. Path Flags .........................................49
         7.1.3. Relation of Operational Flags with Global
                Message Flags ......................................49
         7.1.4. Content Path Selection .............................49
         7.1.5. LFBselect-TLV ......................................49
         7.1.6. OPER-TLV ...........................................50
         7.1.7. RESULT TLV .........................................52
         7.1.8. DATA TLV ...........................................55

Doria, et al. Standards Track [Page 3] RFC 5810 ForCES March 2010

         7.1.9. SET and GET Relationship ...........................56
    7.2. Protocol Encoding Visualization ...........................56
    7.3. Core ForCES LFBs ..........................................59
         7.3.1. FE Protocol LFB ....................................60
         7.3.2. FE Object LFB ......................................63
    7.4. Semantics of Message Direction ............................63
    7.5. Association Messages ......................................64
         7.5.1. Association Setup Message ..........................64
         7.5.2. Association Setup Response Message .................66
         7.5.3. Association Teardown Message .......................68
    7.6. Configuration Messages ....................................69
         7.6.1. Config Message .....................................69
         7.6.2. Config Response Message ............................71
    7.7. Query Messages ............................................73
         7.7.1. Query Message ......................................73
         7.7.2. Query Response Message .............................75
    7.8. Event Notification Message ................................77
    7.9. Packet Redirect Message ...................................79
    7.10. Heartbeat Message ........................................82
 8. High Availability Support ......................................83
    8.1. Relation with the FE Protocol .............................83
    8.2. Responsibilities for HA ...................................86
 9. Security Considerations ........................................87
    9.1. No Security ...............................................87
         9.1.1. Endpoint Authentication ............................88
         9.1.2. Message Authentication .............................88
    9.2. ForCES PL and TML Security Service ........................88
         9.2.1. Endpoint Authentication Service ....................88
         9.2.2. Message Authentication Service .....................89
         9.2.3. Confidentiality Service ............................89
 10. Acknowledgments ...............................................89
 11. References ....................................................89
    11.1. Normative References .....................................89
    11.2. Informative References ...................................90
 Appendix A.  IANA Considerations ..................................91
   A.1.  Message Type Namespace ....................................91
   A.2.  Operation Selection .......................................92
   A.3.  Header Flags ..............................................93
   A.4.  TLV Type Namespace ........................................93
   A.5.  RESULT-TLV Result Values ..................................94
   A.6.  Association Setup Response ................................94
   A.7.  Association Teardown Message ..............................95
 Appendix B.  ForCES Protocol LFB Schema ...........................96
   B.1.  Capabilities .............................................102
   B.2.  Components ...............................................102
 Appendix C.  Data Encoding Examples ..............................103
 Appendix D.  Use Cases ...........................................107

Doria, et al. Standards Track [Page 4] RFC 5810 ForCES March 2010

1. Introduction

 Forwarding and Control Element Separation (ForCES) defines an
 architectural framework and associated protocols to standardize
 information exchange between the control plane and the forwarding
 plane in a ForCES Network Element (ForCES NE).  RFC 3654 has defined
 the ForCES requirements, and RFC 3746 has defined the ForCES
 framework.  While there may be multiple protocols used within the
 overall ForCES architecture, the terms "ForCES protocol" and
 "protocol" as used in this document refer to the protocol used to
 standardize the information exchange between Control Elements (CEs)
 and Forwarding Elements (FEs) only.
 The ForCES FE model [RFC5812] presents a formal way to define FE
 Logical Function Blocks (LFBs) using XML.  LFB configuration
 components, capabilities, and associated events are defined when the
 LFB is formally created.  The LFBs within the FE are accordingly
 controlled in a standardized way by the ForCES protocol.
 This document defines the ForCES protocol specifications.  The ForCES
 protocol works in a master-slave mode in which FEs are slaves and CEs
 are masters.  The protocol includes commands for transport of LFB
 configuration information, association setup, status, event
 notifications, etc.
 Section 3 provides a glossary of terminology used in the
 specification.
 Section 4 provides an overview of the protocol, including a
 discussion on the protocol framework and descriptions of the Protocol
 Layer (PL), a Transport Mapping Layer (TML), and the ForCES protocol
 mechanisms.  Section 4.4 describes several protocol scenarios and
 includes message exchange descriptions.
 While this document does not define the TML, Section 5 details the
 services that a TML MUST provide (TML requirements).
 The ForCES protocol defines a common header for all protocol
 messages.  The header is defined in Section 6.1, while the protocol
 messages are defined in Section 7.
 Section 8 describes the protocol support for high-availability
 mechanisms including redundancy and fail over.
 Section 9 defines the security mechanisms provided by the PL and TML.

Doria, et al. Standards Track [Page 5] RFC 5810 ForCES March 2010

2. Terminology and Conventions

2.1. Requirements Language

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
 document are to be interpreted as described in RFC 2119 [RFC2119].

2.2. Other Notation

 In Table 1 and Table 2, the following notation is used to indicate
 multiplicity:
    (value)+ .... means "1 or more instances of value"
    (value)* .... means "0 or more instances of value"

2.3. Integers

 All integers are to be coded as unsigned binary integers of
 appropriate length.

3. Definitions

 This document follows the terminology defined by the ForCES
 requirements in [RFC3654] and by the ForCES framework in [RFC3746].
 The definitions be are repeated below for clarity.
 Addressable Entity (AE):
 A physical device that is directly addressable given some
 interconnect technology.  For example, on IP networks, it is a device
 that can be reached using an IP address; and on a switch fabric, it
 is a device that can be reached using a switch fabric port number.
 Control Element (CE):
 A logical entity that implements the ForCES protocol and uses it to
 instruct one or more FEs on how to process packets.  CEs handle
 functionality such as the execution of control and signaling
 protocols.

Doria, et al. Standards Track [Page 6] RFC 5810 ForCES March 2010

 CE Manager (CEM):
 A logical entity responsible for generic CE management tasks.  It is
 particularly used during the pre-association phase to determine with
 which FE(s) a CE should communicate.  This process is called FE
 discovery and may involve the CE manager learning the capabilities of
 available FEs.
 Data Path:
 A conceptual path taken by packets within the forwarding plane inside
 an FE.
 Forwarding Element (FE):
 A logical entity that implements the ForCES protocol.  FEs use the
 underlying hardware to provide per-packet processing and handling as
 directed/controlled by one or more CEs via the ForCES protocol.
 FE Model:
 A model that describes the logical processing functions of an FE.
 The FE model is defined using Logical Function Blocks (LFBs).
 FE Manager (FEM):
 A logical entity responsible for generic FE management tasks.  It is
 used during the pre-association phase to determine with which CE(s)
 an FE should communicate.  This process is called CE discovery and
 may involve the FE manager learning the capabilities of available
 CEs.  An FE manager may use anything from a static configuration to a
 pre-association phase protocol (see below) to determine which CE(s)
 to use.  Being a logical entity, an FE manager might be physically
 combined with any of the other logical entities such as FEs.
 ForCES Network Element (NE):
 An entity composed of one or more CEs and one or more FEs.  To
 entities outside an NE, the NE represents a single point of
 management.  Similarly, an NE usually hides its internal organization
 from external entities.

Doria, et al. Standards Track [Page 7] RFC 5810 ForCES March 2010

 High Touch Capability:
 This term will be used to apply to the capabilities found in some
 forwarders to take action on the contents or headers of a packet
 based on content other than what is found in the IP header.  Examples
 of these capabilities include quality of service (QoS) policies,
 virtual private networks, firewall, and L7 content recognition.
 Inter-FE Topology:
 See FE Topology.
 Intra-FE Topology:
 See LFB Topology.
 LFB (Logical Function Block):
 The basic building block that is operated on by the ForCES protocol.
 The LFB is a well-defined, logically separable functional block that
 resides in an FE and is controlled by the CE via the ForCES protocol.
 The LFB may reside at the FE's data path and process packets or may
 be purely an FE control or configuration entity that is operated on
 by the CE.  Note that the LFB is a functionally accurate abstraction
 of the FE's processing capabilities, but not a hardware-accurate
 representation of the FE implementation.
 FE Topology:
 A representation of how the multiple FEs within a single NE are
 interconnected.  Sometimes this is called inter-FE topology, to be
 distinguished from intra-FE topology (i.e., LFB topology).
 LFB Class and LFB Instance:
 LFBs are categorized by LFB classes.  An LFB instance represents an
 LFB class (or type) existence.  There may be multiple instances of
 the same LFB class (or type) in an FE.  An LFB class is represented
 by an LFB class ID, and an LFB instance is represented by an LFB
 instance ID.  As a result, an LFB class ID associated with an LFB
 instance ID uniquely specifies an LFB existence.

Doria, et al. Standards Track [Page 8] RFC 5810 ForCES March 2010

 LFB Meta Data:
 Meta data is used to communicate per-packet state from one LFB to
 another, but is not sent across the network.  The FE model defines
 how such meta data is identified, produced, and consumed by the LFBs.
 It defines the functionality but not how meta data is encoded within
 an implementation.
 LFB Component:
 Operational parameters of the LFBs that must be visible to the CEs
 are conceptualized in the FE model as the LFB components.  The LFB
 components include, for example, flags, single parameter arguments,
 complex arguments, and tables that the CE can read and/or write via
 the ForCES protocol (see below).
 LFB Topology:
 Representation of how the LFB instances are logically interconnected
 and placed along the data path within one FE.  Sometimes it is also
 called intra-FE topology, to be distinguished from inter-FE topology.
 Pre-association Phase:
 The period of time during which an FE manager and a CE manager are
 determining which FE(s) and CE(s) should be part of the same network
 element.
 Post-association Phase:
 The period of time during which an FE knows which CE is to control it
 and vice versa.  This includes the time during which the CE and FE
 are establishing communication with one another.
 ForCES Protocol:
 While there may be multiple protocols used within the overall ForCES
 architecture, the terms "ForCES protocol" and "protocol" refer to the
 Fp reference points in the ForCES framework in [RFC3746].  This
 protocol does not apply to CE-to-CE communication, FE-to-FE
 communication, or communication between FE and CE managers.
 Basically, the ForCES protocol works in a master-slave mode in which
 FEs are slaves and CEs are masters.  This document defines the
 specifications for this ForCES protocol.

Doria, et al. Standards Track [Page 9] RFC 5810 ForCES March 2010

 ForCES Protocol Layer (ForCES PL):
 A layer in the ForCES protocol architecture that defines the ForCES
 protocol messages, the protocol state transfer scheme, and the ForCES
 protocol architecture itself (including requirements of ForCES TML as
 shown below).  Specifications of ForCES PL are defined by this
 document.
 ForCES Protocol Transport Mapping Layer (ForCES TML):
 A layer in ForCES protocol architecture that uses the capabilities of
 existing transport protocols to specifically address protocol message
 transportation issues, such as how the protocol messages are mapped
 to different transport media (like TCP, IP, ATM, Ethernet, etc.), and
 how to achieve and implement reliability, multicast, ordering, etc.
 The ForCES TML specifications are detailed in separate ForCES
 documents, one for each TML.

4. Overview

 The reader is referred to the framework document [RFC3746], and in
 particular, Sections 3 and 4, for an architectural overview and an
 explanation of how the ForCES protocol fits in.  There may be some
 content overlap between the framework document and this section in
 order to provide clarity.  This document is authoritative on the
 protocol, whereas [RFC3746] is authoritative on the architecture.

Doria, et al. Standards Track [Page 10] RFC 5810 ForCES March 2010

4.1. Protocol Framework

 Figure 1 below is reproduced from the framework document for clarity.
 It shows an NE with two CEs and two FEs.
  1. ————————————–

| ForCES Network Element |

  1. ————- Fc | ————– ————– |

| CE Manager |———+-| CE 1 |——| CE 2 | |

  1. ————- | | | Fr | | |

| | ————– ————– |

         | Fl             |         |  |    Fp       /          |
         |                |       Fp|  |----------| /           |
         |                |         |             |/            |
         |                |         |             |             |
         |                |         |     Fp     /|----|        |
         |                |         |  /--------/      |        |
   --------------     Ff  | --------------      --------------  |
   | FE Manager |---------+-|     FE 1   |  Fi  |     FE 2   |  |
   --------------         | |            |------|            |  |
                          | --------------      --------------  |
                          |   |  |  |  |          |  |  |  |    |
                          ----+--+--+--+----------+--+--+--+-----
                              |  |  |  |          |  |  |  |
                              |  |  |  |          |  |  |  |
                                Fi/f                   Fi/f
        Fp: CE-FE interface
        Fi: FE-FE interface
        Fr: CE-CE interface
        Fc: Interface between the CE manager and a CE
        Ff: Interface between the FE manager and an FE
        Fl: Interface between the CE manager and the FE manager
        Fi/f: FE external interface
                Figure 1: ForCES Architectural Diagram
 The ForCES protocol domain is found in the Fp reference points.  The
 Protocol Element configuration reference points, Fc and Ff, also play
 a role in the booting up of the ForCES protocol.  The protocol
 element configuration (indicated by reference points Fc, Ff, and Fl
 in [RFC3746]) is out of scope of the ForCES protocol but is touched
 on in this document in discussion of FEM and CEM since it is an
 integral part of the protocol pre-association phase.

Doria, et al. Standards Track [Page 11] RFC 5810 ForCES March 2010

 Figure 2 below shows further breakdown of the Fp interfaces by means
 of the example of an MPLS QoS-enabled Network Element.
  1. ————————————————

| | | | | | |

       |OSPF   |RIP    |BGP    |RSVP   |LDP    |. . .  |
       |       |       |       |       |       |       |
       -------------------------------------------------    CE
       |               ForCES Interface                |
       -------------------------------------------------
                               ^   ^
                               |   |
                       ForCES  |   |data
                       control |   |packets
                       messages|   |(e.g., routing packets)
                               |   |
                               v   v
       -------------------------------------------------
       |               ForCES Interface                |
       -------------------------------------------------    FE
       |       |       |       |       |       |       |
       |LPM Fwd|Meter  |Shaper |MPLS   |Classi-|. . .  |
       |       |       |       |       |fier   |       |
       -------------------------------------------------
               Figure 2: Examples of CE and FE Functions
 The ForCES interface shown in Figure 2 constitutes two pieces: the PL
 and the TML.

Doria, et al. Standards Track [Page 12] RFC 5810 ForCES March 2010

 This is depicted in Figure 3 below.
       +------------------------------------------------
       |               CE PL                           |
       +------------------------------------------------
       |              CE TML                           |
       +------------------------------------------------
                                 ^
                                 |
                    ForCES       |   (i.e.,  ForCES data + control
                    PL           |    packets )
                    messages     |
                    over         |
                    specific     |
                    TML          |
                    encaps       |
                    and          |
                    transport    |
                                 |
                                 v
       +------------------------------------------------
       |              FE TML                           |
       +------------------------------------------------
       |               FE PL                           |
       +------------------------------------------------
                      Figure 3: ForCES Interface
 The PL is in fact the ForCES protocol.  Its semantics and message
 layout are defined in this document.  The TML layer is necessary to
 connect two ForCES PLs as shown in Figure 3 above.  The TML is out of
 scope for this document but is within scope of ForCES.  This document
 defines requirements the PL needs the TML to meet.
 Both the PL and the TML are standardized by the IETF.  While only one
 PL is defined, different TMLs are expected to be standardized.  To
 interoperate, the TML at the CE and FE are expected to conform to the
 same definition.
 On transmit, the PL delivers its messages to the TML.  The local TML
 delivers the message to the destination TML.  On receive, the TML
 delivers the message to its destination PL.

4.1.1. The PL

 The PL is common to all implementations of ForCES and is standardized
 by the IETF as defined in this document.  The PL is responsible for
 associating an FE or CE to an NE.  It is also responsible for tearing

Doria, et al. Standards Track [Page 13] RFC 5810 ForCES March 2010

 down such associations.  An FE uses the PL to transmit various
 subscribed-to events to the CE PL as well as to respond to various
 status requests issued from the CE PL.  The CE configures both the FE
 and associated LFBs' operational parameters using the PL.  In
 addition, the CE may send various requests to the FE to activate or
 deactivate it, reconfigure its HA parameterization, subscribe to
 specific events, etc.  More details can be found in Section 7.

4.1.2. The TML

 The TML transports the PL messages.  The TML is where the issues of
 how to achieve transport-level reliability, congestion control,
 multicast, ordering, etc. are handled.  It is expected that more than
 one TML will be standardized.  The various possible TMLs could vary
 their implementations based on the capabilities of underlying media
 and transport.  However, since each TML is standardized,
 interoperability is guaranteed as long as both endpoints support the
 same TML.  All ForCES protocol layer implementations MUST be portable
 across all TMLs, because all TMLs MUST have the top-edge semantics
 defined in this document.

4.1.3. The FEM/CEM Interface

 The FEM and CEM components, although valuable in the setup and
 configurations of both the PL and TML, are out of scope of the ForCES
 protocol.  The best way to think of them is as configurations/
 parameterizations for the PL and TML before they become active (or
 even at runtime based on implementation).  In the simplest case, the
 FE or CE reads a static configuration file.  RFC 3746 has a more
 detailed description on how the FEM and CEM could be used.  The pre-
 association phase, where the CEM and FEM can be used, are described
 briefly in Section 4.2.1.
 An example of typical things the FEM/CEM could configure would be
 TML-specific parameterizations such as:
 a.  How the TML connection should happen (for example, what IP
     addresses to use, transport modes, etc.)
 b.  The ID for the FE (FEID) or CE (CEID) (which would also be issued
     during the pre-association phase)
 c.  Security parameterization such as keys, etc.
 d.  Connection association parameters

Doria, et al. Standards Track [Page 14] RFC 5810 ForCES March 2010

 An example of connection association parameters might be:
 o  simple parameters: send up to 3 association messages every 1
    second
 o  complex parameters: send up to 4 association messages with
    increasing exponential timeout

4.2. ForCES Protocol Phases

 ForCES, in relation to NEs, involves two phases: the pre-association
 phase where configuration/initialization/bootup of the TML and PL
 layer happens, and the post-association phase where the ForCES
 protocol operates to manipulate the parameters of the FEs.
                     CE sends Association Setup
         +---->--->------------>---->---->---->------->----+
         |                                                 Y
         ^                                                 |
         |                                                 Y
     +---+-------+                                     +-------------+
     |FE pre-    |                                     | FE post-    |
     |association|    CE sends Association Teardown    | association |
     |phase      |<------- <------<-----<------<-------+ phase       |
     |           |                                     |             |
     +-----------+                                     +-------------+
           ^                                               Y
           |                                               |
           +-<---<------<-----<------<----<---------<------+
                         FE loses association
                   Figure 4: The FE Protocol Phases
 In the mandated case, once associated, the FE may forward packets
 depending on the configuration of its specific LFBs.  An FE that is
 associated to a CE will continue sending packets until it receives an
 Association Teardown Message or until it loses association.  An
 unassociated FE MAY continue sending packets when it has a high
 availability capability.  The extra details are explained in
 Section 8 and not discussed here to allow for a clear explanation of
 the basics.
 The FE state transitions are controlled by means of the FE Object LFB
 FEState component, which is defined in [RFC5812], Section 5.1, and
 also explained in Section 7.3.2.

Doria, et al. Standards Track [Page 15] RFC 5810 ForCES March 2010

 The FE initializes in the FEState OperDisable.  When the FE is ready
 to process packets in the data path, it transitions itself to the
 OperEnable state.
 The CE may decide to pause the FE after it already came up as
 OperEnable.  It does this by setting the FEState to AdminDisable.
 The FE stays in the AdminDisable state until it is explicitly
 configured by the CE to transition to the OperEnable state.
 When the FE loses its association with the CE, it may go into the
 pre-association phase depending on the programmed policy.  For the FE
 to properly complete the transition to the AdminDisable state, it
 MUST stop packet forwarding and this may impact multiple LFBS.  How
 this is achieved is outside the scope of this specification.

4.2.1. Pre-association

 The ForCES interface is configured during the pre-association phase.
 In a simple setup, the configuration is static and is typically read
 from a saved configuration file.  All the parameters for the
 association phase are well known after the pre-association phase is
 complete.  A protocol such as DHCP may be used to retrieve the
 configuration parameters instead of reading them from a static
 configuration file.  Note, this will still be considered static pre-
 association.  Dynamic configuration may also happen using the Fc, Ff,
 and Fl reference points (refer to [RFC3746]).  Vendors may use their
 own proprietary service discovery protocol to pass the parameters.
 Essentially, only guidelines are provided here and the details are
 left to the implementation.
 The following are scenarios reproduced from the framework document to
 show a pre-association example.

Doria, et al. Standards Track [Page 16] RFC 5810 ForCES March 2010

    <----Ff ref pt--->              <--Fc ref pt------->
    FE Manager      FE                CE Manager    CE
     |              |                 |             |
     |              |                 |             |
  (security exchange)               (security exchange)
    1|<------------>| authentication 1|<----------->|authentication
     |              |                 |             |
   (FE ID, components)              (CE ID, components)
    2|<-------------| request        2|<------------|request
     |              |                 |             |
    3|------------->| response       3|------------>|response
    (corresponding CE ID)          (corresponding FE ID)
     |              |                 |             |
     |              |                 |             |
      Figure 5: Examples of a Message Exchange over the Ff and Fc
                           Reference Points
    <-----------Fl ref pt-------------->            |
    FE Manager      FE               CE Manager     CE
     |              |                 |             |
     |              |                 |             |
    (security exchange)               |             |
    1|<------------------------------>|             |
     |              |                 |             |
    (a list of CEs and their components)            |
    2|<-------------------------------|             |
     |              |                 |             |
    (a list of FEs and their components)            |
    3|------------------------------->|             |
     |              |                 |             |
     |              |                 |             |
  Figure 6: Example of a Message Exchange over the Fl Reference Point
 Before the transition to the association phase, the FEM will have
 established contact with a CEM component.  Initialization of the
 ForCES interface will have completed, and authentication as well as
 capability discovery may be complete.  Both the FE and CE would have
 the necessary information for connecting to each other for
 configuration, accounting, identification, and authentication
 purposes.  To summarize, at the completion of this stage both sides
 have all the necessary protocol parameters such as timers, etc.  The
 Fl reference point may continue to operate during the association
 phase and may be used to force a disassociation of an FE or CE.  The
 specific interactions of the CEM and the FEM that are part of the

Doria, et al. Standards Track [Page 17] RFC 5810 ForCES March 2010

 pre-association phase are out of scope; for this reason, these
 details are not discussed any further in this specification.  The
 reader is referred to the framework document [RFC3746] for a slightly
 more detailed discussion.

4.2.2. Post-association

 In this phase, the FE and CE components communicate with each other
 using the ForCES protocol (PL over TML) as defined in this document.
 There are three sub-phases:
 o  Association Setup Stage
 o  Established Stage
 o  Association Lost Stage

4.2.2.1. Association Setup Stage

 The FE attempts to join the NE.  The FE may be rejected or accepted.
 Once granted access into the NE, capabilities exchange happens with
 the CE querying the FE.  Once the CE has the FE capability
 information, the CE can offer an initial configuration (possibly to
 restore state) and can query certain components within either an LFB
 or the FE itself.
 More details are provided in Section 4.4.
 On successful completion of this stage, the FE joins the NE and is
 moved to the Established Stage.

4.2.2.2. Established Stage

 In this stage, the FE is continuously updated or queried.  The FE may
 also send asynchronous event notifications to the CE or synchronous
 heartbeat notifications if programmed to do so.  This stage continues
 until a termination occurs, either due to loss of connectivity or due
 to a termination initiated by either the CE or the FE.
 Refer to the section on protocol scenarios, Section 4.4, for more
 details.

4.2.2.3. Association Lost Stage

 In this stage, both or either the CE or FE declare the other side is
 no longer associated.  The disconnection could be initiated by either
 party for administrative purposes but may also be driven by
 operational reasons such as loss of connectivity.

Doria, et al. Standards Track [Page 18] RFC 5810 ForCES March 2010

 A core LFB known as the FE Protocol Object (FEPO) is defined (refer
 to Appendix B and Section 7.3.1).  FEPO defines various timers that
 can be used in conjunction with a traffic-sensitive heartbeat
 mechanism (Section 4.3.3) to detect loss of connectivity.
 The loss of connectivity between TMLs does not indicate a loss of
 association between respective PL layers.  If the TML cannot repair
 the transport loss before the programmed FEPO timer thresholds
 associated with the FE is exceeded, then the association between the
 respective PL layers will be lost.
 FEPO defines several policies that can be programmed to define
 behavior upon a detected loss of association.  The FEPO's programmed
 CE failover policy (refer to Sections 8, 7.3.1, 4.3.3, and B) defines
 what takes place upon loss of association.
 For this version of the protocol (as defined in this document), the
 FE, upon re-association, MUST discard any state it has as invalid and
 retrieve new state.  This approach is motivated by a desire for
 simplicity (as opposed to efficiency).

4.3. Protocol Mechanisms

 Various semantics are exposed to the protocol users via the PL header
 including transaction capabilities, atomicity of transactions, two-
 phase commits, batching/parallelization, high availability, and
 failover as well as command pipelines.
 The EM (Execution Mode) flag, AT (Atomic Transaction) flag, and TP
 (Transaction Phase) flag as defined in the common header
 (Section 6.1) are relevant to these mechanisms.

4.3.1. Transactions, Atomicity, Execution, and Responses

 In the master-slave relationship, the CE instructs one or more FEs on
 how to execute operations and how to report the results.
 This section details the different modes of execution that a CE can
 order the FE(s) to perform, as defined in Section 4.3.1.1.  It also
 describes the different modes a CE can ask the FE(s) to use for
 formatting the responses after processing the operations as
 requested.  These modes relate to the transactional two-phase commit
 operations.

Doria, et al. Standards Track [Page 19] RFC 5810 ForCES March 2010

4.3.1.1. Execution

 There are 3 execution modes that can be requested for a batch of
 operations spanning one or more LFB selectors (refer to
 Section 7.1.5) in one protocol message.  The EM flag defined in the
 common header (Section 6.1) selects the execution mode for a protocol
 message, as below:
 a.  execute-all-or-none
 b.  continue-execute-on-failure
 c.  execute-until-failure

4.3.1.1.1. execute-all-or-none

 When set to this mode of execution, independent operations in a
 message MAY be targeted at one or more LFB selectors within an FE.
 All these operations are executed serially, and the FE MUST have no
 execution failure for any of the operations.  If any operation fails
 to execute, then all the previous ones that have been executed prior
 to the failure will need to be undone.  That is, there is rollback
 for this mode of operation.
 Refer to Section 4.3.1.2.2 for how this mode is used in cases of
 transactions.  In such a case, no operation is executed unless a
 commit is issued by the CE.
 Care should be taken on how this mode is used because a mis-
 configuration could result in traffic losses.  To add certainty to
 the success of an operation, one should use this mode in a
 transactional operation as described in Section 4.3.1.2.2

4.3.1.1.2. continue-execute-on-failure

 If several independent operations are targeted at one or more LFB
 selectors, execution continues for all operations at the FE even if
 one or more operations fail.

4.3.1.1.3. execute-until-failure

 In this mode, all operations are executed on the FE sequentially
 until the first failure.  The rest of the operations are not executed
 but operations already completed are not undone.  That is, there is
 no rollback in this mode of operation.

Doria, et al. Standards Track [Page 20] RFC 5810 ForCES March 2010

4.3.1.2. Transaction and Atomicity

4.3.1.2.1. Transaction Definition

 A transaction is defined as a collection of one or more ForCES
 operations within one or more PL messages that MUST meet the ACIDity
 properties [ACID], defined as:
 Atomicity:   In a transaction involving two or more discrete pieces
              of information, either all of the pieces are committed
              or none are.
 Consistency: A transaction either creates a new and valid state of
              data or, if any failure occurs, returns all data to the
              state it was in before the transaction was started.
 Isolation:   A transaction in process and not yet committed MUST
              remain isolated from any other transaction.
 Durability:  Committed data is saved by the system such that, even in
              the event of a failure and a system restart, the data is
              available in its correct state.
 There are cases where the CE knows exact memory and implementation
 details of the FE such as in the case of an FE-CE pair from the same
 vendor where the FE-CE pair is tightly coupled.  In such a case, the
 transactional operations may be simplified further by extra
 computation at the CE.  This view is not discussed further other than
 to mention that it is not disallowed.
 As defined above, a transaction is always atomic and MAY be
 a.  Within an FE alone
     Example: updating multiple tables that are dependent on each
     other.  If updating one fails, then any that were already updated
     MUST be undone.
 b.  Distributed across the NE
     Example: updating table(s) that are inter-dependent across
     several FEs (such as L3 forwarding-related tables).

4.3.1.2.2. Transaction Protocol

 By use of the execution mode, as defined in Section 4.3.1.1, the
 protocol has provided a mechanism for transactional operations within
 one stand-alone message.  The 'execute-all-or-none' mode can meet the
 ACID requirements.

Doria, et al. Standards Track [Page 21] RFC 5810 ForCES March 2010

 For transactional operations of multiple messages within one FE or
 across FEs, a classical transactional protocol known as two-phase
 commit (2PC) [2PCREF] is supported by the protocol to achieve the
 transactional operations utilizing Config messages (Section 7.6.1).
 The COMMIT and TRCOMP operations in conjunction with the AT and the
 TP flags in the common header (Section 6.1) are provided for 2PC-
 based transactional operations spanning multiple messages.
 The AT flag, when set, indicates that this message belongs to an
 Atomic Transaction.  All messages for a transaction operation MUST
 have the AT flag set.  If not set, it means that the message is a
 stand-alone message and does not participate in any transaction
 operation that spans multiple messages.
 The TP flag indicates the Transaction Phase to which this message
 belongs.  There are 4 possible phases for a transactional operation
 known as:
    SOT (Start of Transaction)
    MOT (Middle of Transaction)
    EOT (End of Transaction)
    ABT (Abort)
 The COMMIT operation is used by the CE to signal to the FE(s) to
 commit a transaction.  When used with an ABT TP flag, the COMMIT
 operation signals the FE(s) to roll back (i.e., un-COMMIT) a
 previously committed transaction.
 The TRCOMP operation is a small addition to the classical 2PC
 approach.  TRCOMP is sent by the CE to signal to the FE(s) that the
 transaction they have COMMITed is now over.  This allows the FE(s) an
 opportunity to clear state they may have kept around to perform a
 roll back (if it became necessary).
 A transaction operation is started with a message in which the TP
 flag is set to Start of Transaction (SOT).  Multi-part messages,
 after the first one, are indicated by the Middle of Transaction (MOT)
 flag.  All messages from the CE MUST set the AlwaysACK flag
 (Section 6) to solicit responses from the FE(s).
 Before the CE issues a commit (described further below), the FE MUST
 only validate that the operation can be executed but not execute it.

Doria, et al. Standards Track [Page 22] RFC 5810 ForCES March 2010

    Any failure notified by an FE causes the CE to abort the
    transaction on all FEs involved in the transaction.  This is
    achieved by sending a Config message with an ABT flag and a COMMIT
    operation.
    If there are no failures by any participating FE, the transaction
    commitment phase is signaled from the CE to the FE by an End of
    Transaction (EOT) configuration message with a COMMIT operation.
 The FE MUST respond to the CE's EOT message.  There are two possible
 failure scenarios in which the CE MUST abort the transaction (as
 described above):
 a.  If any participating FE responds with a failure message in
     relation to the transaction.
 b.  If no response is received from a participating FE within a
     specified timeout.
 If all participating FEs respond with a success indicator within the
 expected time, then the CE MUST issue a TRCOMP operation to all
 participating FEs.  An FE MUST NOT respond to a TRCOMP.
 Note that a transactional operation is generically atomic; therefore,
 it requires that the execution modes of all messages in a transaction
 operation should always be kept the same and be set to 'execute-all-
 or-none'.  If the EM flag is set to other execution modes, it will
 result in a transaction failure.
 As noted above, a transaction may span multiple messages.  It is up
 to the CE to keep track of the different outstanding messages making
 up a transaction.  As an example, the correlator field could be used
 to mark transactions and a sequence field to label the different
 messages within the same atomic transaction, but this is out of scope
 and up to implementations.

4.3.1.2.3. Recovery

 Any of the participating FEs or the CE or the associations between
 them may fail after the EOT Response message has been sent by the FE
 but before the CE has received all the responses, e.g., if the EOT
 response never reaches the CE.
 In this protocol revision, as indicated in Section 4.2.2.3, an FE
 losing an association would be required to get entirely new state
 from the newly associated CE upon a re-association.  Although this
 approach is simplistic and provides likeliness of losing data path

Doria, et al. Standards Track [Page 23] RFC 5810 ForCES March 2010

 traffic, it is a design choice to avoid the additional complexity of
 managing graceful restarts.  The HA mechanisms (Section 8) are
 provided to allow for a continuous operation in case of FE failures.
 Flexibility is provided on how to react when an FE loses association.
 This is dictated by the CE failover policy (refer to Section 8 and
 Section 7.3).

4.3.1.2.4. Transaction Messaging Example

 This section illustrates an example of how a successful two-phase
 commit between a CE and an FE would look in the simple case.
       FE PL                                                  CE PL
         |                                                      |
         | (1) Config, SOT,AT, EM=All-or-None, OP= SET/DEL,etc  |
         |<-----------------------------------------------------|
         |                                                      |
         | (2) ACKnowledge                                      |
         |----------------------------------------------------->|
         |                                                      |
         | (3) Config, MOT,AT, EM=All-or-None, OP= SET/DEL,etc  |
         |<-----------------------------------------------------|
         |                                                      |
         | (4) ACKnowledge                                      |
         |----------------------------------------------------->|
         |                                                      |
         | (5) Config, MOT,AT, EM=All-or-None, OP= SET/DEL,etc  |
         |<-----------------------------------------------------|
         |                                                      |
         | (6) ACKnowledge                                      |
         |----------------------------------------------------->|
         .                                                      .
         .                                                      .
         .                                                      .
         .                                                      .
         |                                                      |
         | (N) Config, EOT,AT, EM=All-or-None, OP= COMMIT       |
         |<-----------------------------------------------------|
         |                                                      |
         | (N+1)Config-response, ACKnowledge, OP=COMMIT-RESPONSE|
         |----------------------------------------------------->|
         |                                                      |
         | (N+2) Config, OP=TRCOMP                              |
         |<-----------------------------------------------------|
                Figure 7: Example of a Two-Phase Commit

Doria, et al. Standards Track [Page 24] RFC 5810 ForCES March 2010

 For the scenario illustrated above:
 o  In step 1, the CE issues a Config message with an operation of
    choice like a DEL or SET.  The transaction flags are set to
    indicate a Start of Transaction (SOT), Atomic Transaction (AT),
    and execute-all-or-none.
 o  The FE validates that it can execute the request successfully and
    then issues an acknowledgment back to the CE in step 2.
 o  In step 3, the same sort of construct as in step 1 is repeated by
    the CE with the transaction flag changed to Middle of Transaction
    (MOT).
 o  The FE validates that it can execute the request successfully and
    then issues an acknowledgment back to the CE in step 4.
 o  The CE-FE exchange continues in the same manner until all the
    operations and their parameters are transferred to the FE.  This
    happens in step (N-1).
 o  In step N, the CE issues a commit.  A commit is a Config message
    with an operation of type COMMIT.  The transaction flag is set to
    End of Transaction (EOT).  Essentially, this is an "empty" message
    asking the FE to execute all the operations it has gathered since
    the beginning of the transaction (message #1).
 o  The FE at this point executes the full transaction.  It then
    issues an acknowledgment back to the CE in step (N+1) that
    contains a COMMIT-RESPONSE.
 o  The CE in this case has the simple task of issuing a TRCOMP
    operation to the FE in step (N+2).

4.3.2. Scalability

 It is desirable that the PL not become the bottleneck when larger
 bandwidth pipes become available.  To pick a hypothetical example in
 today's terms, if a 100-Gbps pipe is available and there is
 sufficient work, then the PL should be able to take advantage of this
 and use all of the 100-Gbps pipe.  Two mechanisms have been provided
 to achieve this.  The first one is batching and the second one is a
 command pipeline.

Doria, et al. Standards Track [Page 25] RFC 5810 ForCES March 2010

 Batching is the ability to send multiple commands (such as Config) in
 one Protocol Data Unit (PDU).  The size of the batch will be affected
 by, among other things, the path MTU.  The commands may be part of
 the same transaction or may be part of unrelated transactions that
 are independent of each other.
 Command pipelining allows for pipelining of independent transactions
 that do not affect each other.  Each independent transaction could
 consist of one or more batches.

4.3.2.1. Batching

 There are several batching levels at different protocol hierarchies.
 o  Multiple PL PDUs can be aggregated under one TML message.
 o  Multiple LFB classes and instances (as indicated in the LFB
    selector) can be addressed within one PL PDU.
 o  Multiple operations can be addressed to a single LFB class and
    instance.

4.3.2.2. Command Pipelining

 The protocol allows any number of messages to be issued by the CE
 before the corresponding acknowledgments (if requested) have been
 returned by the FE.  Hence, pipelining is inherently supported by the
 protocol.  Matching responses with requests messages can be done
 using the correlator field in the message header.

4.3.3. Heartbeat Mechanism

 Heartbeats (HBs) between FEs and CEs are traffic sensitive.  An HB is
 sent only if no PL traffic is sent between the CE and FE within a
 configured interval.  This has the effect of reducing the amount of
 HB traffic in the case of busy PL periods.
 An HB can be sourced by either the CE or FE.  When sourced by the CE,
 a response can be requested (similar to the ICMP ping protocol).  The
 FE can only generate HBs in the case of being configured to do so by
 the CE.  Refer to Section 7.3.1 and Section 7.10 for details.

Doria, et al. Standards Track [Page 26] RFC 5810 ForCES March 2010

4.3.4. FE Object and FE Protocol LFBs

 All PL messages operate on LFB constructs, as this provides more
 flexibility for future enhancements.  This means that maintenance and
 configurability of FEs, NE, and the ForCES protocol itself MUST be
 expressed in terms of this LFB architecture.  For this reason,
 special LFBs are created to accommodate this need.
 In addition, this shows how the ForCES protocol itself can be
 controlled by the very same type of structures (LFBs) it uses to
 control functions such as IP forwarding, filtering, etc.
 To achieve this, the following specialized LFBs are introduced:
 o  FE Protocol LFB, which is used to control the ForCES protocol.
 o  FE Object LFB, which is used to control components relative to the
    FE itself.  Such components include FEState [RFC5812], vendor,
    etc.
 These LFBs are detailed in Section 7.3.

4.4. Protocol Scenarios

 This section provides a very high level description of sample message
 sequences between a CE and an FE.  For protocol message encoding
 refer to Section 6.1, and for the semantics of the protocol refer to
 Section 4.3.

4.4.1. Association Setup State

 The associations among CEs and FEs are initiated via the Association
 Setup message from the FE.  If a Setup Request is granted by the CE,
 a successful Setup Response message is sent to the FE.  If CEs and
 FEs are operating in an insecure environment, then the security
 associations have to be established between them before any
 association messages can be exchanged.  The TML MUST take care of
 establishing any security associations.
 This is typically followed by capability query, topology query, etc.
 When the FE is ready to start processing the data path, it sets the
 FEO FEState component to OperEnable (refer to [RFC5812] for details)
 and reports it to the CE as such when it is first queried.
 Typically, the FE is expected to be ready to process the data path
 before it associates, but there may be rare cases where it needs time
 do some pre-processing -- in such a case, the FE will start in the
 OperDisable state and when it is ready will transition to the
 OperEnable state.  An example of an FE starting in OperDisable then

Doria, et al. Standards Track [Page 27] RFC 5810 ForCES March 2010

 transitioning to OperEnable is illustrated in Figure 8.  The CE could
 at any time also disable the FE's data path operations by setting the
 FEState to AdminDisable.  The FE MUST NOT process packets during this
 state unless the CE sets the state back to OperEnable.  These
 sequences of messages are illustrated in Figure 8 below.
         FE PL                  CE PL
           |                       |
           |   Asso Setup Req      |
           |---------------------->|
           |                       |
           |   Asso Setup Resp     |
           |<----------------------|
           |                       |
           | LFBx Query capability |
           |<----------------------|
           |                       |
           | LFBx Query Resp       |
           |---------------------->|
           |                       |
           | FEO Query (Topology)  |
           |<----------------------|
           |                       |
           | FEO Query Resp        |
           |---------------------->|
           |                       |
           | FEO OperEnable Event  |
           |---------------------->|
           |                       |
           |  Config FEO Adminup   |
           |<----------------------|
           |                       |
           | FEO Config-Resp       |
           |---------------------->|
           |                       |
 Figure 8: Message Exchange between CE and FE to Establish
 an NE Association
 On successful completion of this state, the FE joins the NE.

Doria, et al. Standards Track [Page 28] RFC 5810 ForCES March 2010

4.4.2. Association Established State or Steady State

 In this state, the FE is continuously updated or queried.  The FE may
 also send asynchronous event notifications to the CE, synchronous
 Heartbeat messages, or Packet Redirect message to the CE.  This
 continues until a termination (or deactivation) is initiated by
 either the CE or FE.  Figure 9 below, helps illustrate this state.

Doria, et al. Standards Track [Page 29] RFC 5810 ForCES March 2010

         FE PL                          CE PL
           |                              |
           |    Heartbeat                 |
           |<---------------------------->|
           |                              |
           |   Heartbeat                  |
           |----------------------------->|
           |                              |
           | Config-set LFBy (Event sub.) |
           |<-----------------------------|
           |                              |
           |     Config Resp LFBy         |
           |----------------------------->|
           |                              |
           |  Config-set LFBx Component   |
           |<-----------------------------|
           |                              |
           |     Config Resp  LFBx        |
           |----------------------------->|
           |                              |
           |Config-Query LFBz (Stats)     |
           |<--------------------------- -|
           |                              |
           |    Query Resp LFBz           |
           |----------------------------->|
           |                              |
           |    FE Event Report           |
           |----------------------------->|
           |                              |
           |  Config-Del LFBx Component   |
           |<-----------------------------|
           |                              |
           |     Config Resp LFBx         |
           |----------------------------->|
           |                              |
           |    Packet Redirect LFBx      |
           |----------------------------->|
           |                              |
           |    Heartbeat                 |
           |<-----------------------------|
           .                              .
           .                              .
           |                              |
 Figure 9: Message Exchange between CE and FE during
 Steady-State Communication

Doria, et al. Standards Track [Page 30] RFC 5810 ForCES March 2010

 Note that the sequence of messages shown in the figure serve only as
 examples and the message exchange sequences could be different from
 what is shown in the figure.  Also, note that the protocol scenarios
 described in this section do not include all the different message
 exchanges that would take place during failover.  That is described
 in the HA section (Section 8).

5. TML Requirements

 The requirements below are expected to be met by the TML.  This text
 does not define how such mechanisms are delivered.  As an example,
 the mechanisms to meet the requirements could be defined to be
 delivered via hardware or between 2 or more TML software processes on
 different CEs or FEs in protocol-level schemes.
 Each TML MUST describe how it contributes to achieving the listed
 ForCES requirements.  If for any reason a TML does not provide a
 service listed below, a justification needs to be provided.
 Implementations that support the ForCES protocol specification MUST
 implement [RFC5811].  Note that additional TMLs might be specified in
 the future, and if a new TML defined in the future that meets the
 requirements listed here proves to be better, then the "MUST
 implement TML" may be redefined.
 1.  Reliability
     Various ForCES messages will require varying degrees of reliable
     delivery via the TML.  It is the TML's responsibility to provide
     these shades of reliability and describe how the different ForCES
     messages map to reliability.
     The most common level of reliability is what we refer to as
     strict or robust reliability in which we mean no losses,
     corruption, or re-ordering of information being transported while
     ensuring message delivery in a timely fashion.
     Payloads such as configuration from a CE and its response from an
     FE are mission critical and must be delivered in a robust
     reliable fashion.  Thus, for information of this sort, the TML
     MUST either provide built-in protocol mechanisms or use a
     reliable transport protocol for achieving robust/strict
     reliability.

Doria, et al. Standards Track [Page 31] RFC 5810 ForCES March 2010

     Some information or payloads, such as redirected packets or
     packet sampling, may not require robust reliability (can tolerate
     some degree of losses).  For information of this sort, the TML
     could define to use a mechanism that is not strictly reliable
     (while conforming to other TML requirements such as congestion
     control).
     Some information or payloads, such as heartbeat packets, may
     prefer timeliness over reliable delivery.  For information of
     this sort, the TML could define to use a mechanism that is not
     strictly reliable (while conforming to other TML requirements
     such as congestion control).
 2.  Security
     TML provides security services to the ForCES PL.  Because a
     ForCES PL is used to operate an NE, attacks designed to confuse,
     disable, or take information from a ForCES-based NE may be seen
     as a prime objective during a network attack.
     An attacker in a position to inject false messages into a PL
     stream can affect either the FE's treatment of the data path (for
     example, by falsifying control data reported as coming from the
     CE) or the CE itself (by modifying events or responses reported
     as coming from the FE).  For this reason, CE and FE node
     authentication and TML message authentication are important.
     The PL messages may also contain information of value to an
     attacker, including information about the configuration of the
     network, encryption keys, and other sensitive control data, so
     care must be taken to confine their visibility to authorized
     users.
  • The TML MUST provide a mechanism to authenticate ForCES CEs

and FEs, in order to prevent the participation of unauthorized

        CEs and unauthorized FEs in the control and data path
        processing of a ForCES NE.
  • The TML SHOULD provide a mechanism to ensure message

authentication of PL data transferred from the CE to FE (and

        vice versa), in order to prevent the injection of incorrect
        data into PL messages.
  • The TML SHOULD provide a mechanism to ensure the

confidentiality of data transferred from the ForCES PL, in

        order to prevent disclosure of PL-level information
        transported via the TML.

Doria, et al. Standards Track [Page 32] RFC 5810 ForCES March 2010

     The TML SHOULD provide these services by employing TLS or IPsec.
 3.  Congestion control
     The transport congestion control scheme used by the TML needs to
     be defined.  The congestion control mechanism defined by the TML
     MUST prevent transport congestive collapse [RFC2914] on either
     the FE or CE side.
 4.  Uni/multi/broadcast addressing/delivery, if any
     If there is any mapping between PL- and TML-level uni/multi/
     broadcast addressing, it needs to be defined.
 5.  HA decisions
     It is expected that availability of transport links is the TML's
     responsibility.  However, based upon its configuration, the PL
     may wish to participate in link failover schemes and therefore
     the TML MUST support this capability.
     Please refer to Section 8 for details.
 6.  Encapsulations used
     Different types of TMLs will encapsulate the PL messages on
     different types of headers.  The TML needs to specify the
     encapsulation used.
 7.  Prioritization
     It is expected that the TML will be able to handle up to 8
     priority levels needed by the PL and will provide preferential
     treatment.
     While the TML needs to define how this is achieved, it should be
     noted that the requirement for supporting up to 8 priority levels
     does not mean that the underlying TML MUST be capable of
     providing up to 8 actual priority levels.  In the event that the
     underlying TML layer does not have support for 8 priority levels,
     the supported priority levels should be divided between the
     available TML priority levels.  For example, if the TML only
     supports 2 priority levels, 0-3 could go in one TML priority
     level, while 4-7 could go in the other.
     The TML MUST NOT re-order config packets with the same priority.

Doria, et al. Standards Track [Page 33] RFC 5810 ForCES March 2010

 8.  Node Overload Prevention
     The TML MUST define mechanisms it uses to help prevent node
     overload.
     Overload results in starvation of node compute cycles and/or
     bandwidth resources, which reduces the operational capacity of a
     ForCES NE.  NE node overload could be deliberately instigated by
     a hostile node to attack a ForCES NE and create a denial of
     service (DoS).  It could also be created by a variety of other
     reasons such as large control protocol updates (e.g., BGP flaps),
     which consequently cause a high frequency of CE to FE table
     updates, HA failovers, or component failures, which migrate an FE
     or CE load overwhelming the new CE or FE, etc.  Although the
     environments under which SIP and ForCES operate are different,
     [RFC5390] provides a good guide to generic node requirements one
     needs to guard for.
     A ForCES node CPU may be overwhelmed because the incoming packet
     rate is higher than it can keep up with -- in such a case, a
     node's transport queues grow and transport congestion
     subsequently follows.  A ForCES node CPU may also be adversely
     overloaded with very few packets, i.e., no transport congestion
     at all (e.g., a in a DoS attack against a table hashing algorithm
     that overflows the table and/or keeps the CPU busy so it does not
     process other tasks).  The TML node overload solution specified
     MUST address both types of node overload scenarios.

5.1. TML Parameterization

 It is expected that it should be possible to use a configuration
 reference point, such as the FEM or the CEM, to configure the TML.
 Some of the configured parameters may include:
 o  PL ID
 o  Connection Type and associated data.  For example, if a TML uses
    IP/TCP/UDP, then parameters such as TCP and UDP port and IP
    addresses need to be configured.
 o  Number of transport connections
 o  Connection capability, such as bandwidth, etc.
 o  Allowed/supported connection QoS policy (or congestion control
    policy)

Doria, et al. Standards Track [Page 34] RFC 5810 ForCES March 2010

6. Message Encapsulation

 All PL PDUs start with a common header Section 6.1 followed by one or
 more TLVs Section 6.2, which may nest other TLVs Section 6.2.1.  All
 fields are in network byte order.

6.1. Common Header

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |version| rsvd  | Message Type  |             Length            |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                          Source ID                            |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                        Destination ID                         |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                        Correlator[63:32]                      |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                        Correlator[31:0]                       |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                             Flags                             |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                       Figure 10: Common Header
 The message is 32-bit aligned.
 Version (4 bits):
    Version number.  Current version is 1.
 rsvd (4 bits):
    Unused at this point.  A receiver should not interpret this field.
    Senders MUST set it to zero and receivers MUST ignore this field.
 Message Type (8 bits):
    Commands are defined in Section 7.
 Length (16 bits):
    length of header + the rest of the message in DWORDS (4-byte
    increments).
 Source ID  (32 bits):

Doria, et al. Standards Track [Page 35] RFC 5810 ForCES March 2010

 Dest ID (32 bits):
  • Each of the source and destination IDs are 32-bit IDs that are

unique NE-wide and that identify the termination points of a

        ForCES PL message.
  • IDs allow multi/broad/unicast addressing with the following

approach:

        a.  A split address space is used to distinguish FEs from CEs.
            Even though in a large NE there are typically two or more
            orders of magnitude of more FEs than CEs, the address
            space is split uniformly for simplicity.
        b.  The address space allows up to 2^30 (over a billion) CEs
            and the same amount of FEs.
 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |TS |                           sub-ID                          |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
           Figure 11: ForCES ID Format
         c.  The 2 most significant bits called Type Switch (TS) are
           used to split the ID space as follows:
 TS        Corresponding ID range       Assignment
 --        ----------------------       ----------
 0b00      0x00000000 to 0x3FFFFFFF     FE IDs (2^30)
 0b01      0x40000000 to 0x7FFFFFFF     CE IDs (2^30)
 0b10      0x80000000 to 0xBFFFFFFF     reserved
 0b11      0xC0000000 to 0xFFFFFFEF     multicast IDs (2^30 - 16)
 0b11      0xFFFFFFF0 to 0xFFFFFFFC     reserved
 0b11      0xFFFFFFFD                   all CEs broadcast
 0b11      0xFFFFFFFE                   all FEs broadcast
 0b11      0xFFFFFFFF                   all FEs and CEs (NE) broadcast
           Figure 12: Type Switch ID Space
  • Multicast or broadcast IDs are used to group endpoints (such

as CEs and FEs). As an example, one could group FEs in some

        functional group, by assigning a multicast ID.  Likewise,
        subgroups of CEs that act, for instance, in a back-up mode may
        be assigned a multicast ID to hide them from the FE.

Doria, et al. Standards Track [Page 36] RFC 5810 ForCES March 2010

        +   Multicast IDs can be used for both source or destination
            IDs.
        +   Broadcast IDs can be used only for destination IDs.
  • This document does not discuss how a particular multicast ID

is associated to a given group though it could be done via

        configuration process.  The list of IDs an FE owns or is part
        of are listed on the FE Object LFB.
 Correlator (64 bits):
    This field is set by the CE to correlate ForCES Request messages
    with the corresponding Response messages from the FE.
    Essentially, it is a cookie.  The correlator is handled
    transparently by the FE, i.e., for a particular Request message
    the FE MUST assign the same correlator value in the corresponding
    Response message.  In the case where the message from the CE does
    not elicit a response, this field may not be useful.
    The correlator field could be used in many implementations in
    specific ways by the CE.  For example, the CE could split the
    correlator into a 32-bit transactional identifier and 32-bit
    message sequence identifier.  Another example is a 64-bit pointer
    to a context block.  All such implementation-specific uses of the
    correlator are outside the scope of this specification.
    It should be noted that the correlator is transmitted on the
    network as if it were a 64-bit unsigned integer with the leftmost
    or most significant octet (bits 63-56) transmitted first.
    Whenever the correlator field is not relevant, because no message
    is expected, the correlator field is set to 0.
 Flags (32 bits):
 Identified so far:
 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |   |     |     |   | |   |                                     |
 |ACK| Pri |Rsr  |EM |A|TP |     Reserved                        |
 |   |     | vd. |   |T|   |                                     |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
           Figure 13: Header Flags
  1. ACK: ACK indicator (2 bits)

Doria, et al. Standards Track [Page 37] RFC 5810 ForCES March 2010

 The ACK indicator flag is only used by the CE when sending a Config
 message (Section 7.6.1) or an HB message (Section 7.10) to indicate
 to the message receiver whether or not a response is required by the
 sender.  Note that for all other messages than the Config message or
 the HB message this flag MUST be ignored.
 The flag values are defined as follows:
    'NoACK' (0b00) - to indicate that the message receiver MUST NOT
    send any Response message back to this message sender.
    'SuccessACK'(0b01) - to indicate that the message receiver MUST
    send a Response message back only when the message has been
    successfully processed by the receiver.
    'FailureACK'(0b10) - to indicate that the message receiver MUST
    send a Response message back only when there is failure by the
    receiver in processing (executing) the message.  In other words,
    if the message can be processed successfully, the sender will not
    expect any response from the receiver.
    'AlwaysACK' (0b11) - to indicate that the message receiver MUST
    send a Response message.
 Note that in above definitions, the term success implies a complete
 execution without any failure of the message.  Anything else than a
 complete successful execution is defined as a failure for the message
 processing.  As a result, for the execution modes (defined in
 Section 4.3.1.1) like execute-all-or-none, execute-until-failure, and
 continue-execute-on-failure, if any single operation among several
 operations in the same message fails, it will be treated as a failure
 and result in a response if the ACK indicator has been set to
 'FailureACK' or 'AlwaysACK'.
 Also note that, other than in Config and HB messages, requirements
 for responses of messages are all given in a default way rather than
 by ACK flags.  The default requirements of these messages and the
 expected responses are summarized below.  Detailed descriptions can
 be found in the individual message definitions:
         +   Association Setup message always expects a response.
         +   Association Teardown Message, and Packet Redirect
             message, never expect responses.
         +   Query message always expects a response.
         +   Response message never expects further responses.

Doria, et al. Standards Track [Page 38] RFC 5810 ForCES March 2010

  1. Pri: Priority (3 bits)
 ForCES protocol defines 8 different levels of priority (0-7).  The
 priority level can be used to distinguish between different protocol
 message types as well as between the same message type.  The higher
 the priority value, the more important the PDU is.  For example, the
 REDIRECT packet message could have different priorities to
 distinguish between routing protocol packets and ARP packets being
 redirected from FE to CE.  The normal priority level is 1.  The
 different priorities imply messages could be re-ordered; however,
 re-ordering is undesirable when it comes to a set of messages within
 a transaction and caution should be exercised to avoid this.
  1. EM: Execution Mode (2 bits)
 There are 3 execution modes; refer to Section 4.3.1.1 for details.
    Reserved..................... (0b00)
    `execute-all-or-none` ....... (0b01)
    `execute-until-failure` ..... (0b10)
    `continue-execute-on-failure` (0b11)
  1. AT: Atomic Transaction (1 bit)
 This flag indicates if the message is a stand-alone message or one of
 multiple messages that belong to 2PC transaction operations.  See
 Section 4.3.1.2.2 for details.
    Stand-alone message ......... (0b0)
    2PC transaction message ..... (0b1)
  1. TP: Transaction Phase (2 bits)
 A message from the CE to the FE within a transaction could be
 indicative of the different phases the transaction is in.  Refer to
 Section 4.3.1.2.2 for details.
    SOT (start of transaction) ..... (0b00)
    MOT (middle of transaction) .... (0b01)
    EOT (end of transaction) ........(0b10)
    ABT (abort) .....................(0b11)

Doria, et al. Standards Track [Page 39] RFC 5810 ForCES March 2010

6.2. Type Length Value (TLV) Structuring

 TLVs are extensively used by the ForCES protocol.  TLVs have some
 very nice properties that make them a good candidate for encoding the
 XML definitions of the LFB class model.  These are:
 o  Providing for binary type-value encoding that is close to the XML
    string tag-value scheme.
 o  Allowing for fast generalized binary-parsing functions.
 o  Allowing for forward and backward tag compatibility.  This is
    equivalent to the XML approach, i.e., old applications can ignore
    new TLVs and newer applications can ignore older TLVs.
 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | TLV Type                    | TLV Length                      |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |            Value (Essentially the TLV Data)                   |
 ~                                                               ~
 ~                                                               ~
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                     Figure 14: TLV Representation
 TLV Type (16):
 The TLV type field is 2 octets, and semantically indicates the type
 of data encapsulated within the TLV.
 TLV Length (16):
 The TLV length field is 2 octets, and includes the length of the TLV
 type (2 octets), TLV Length (2 octets), and the length of the TLV
 data found in the value field, in octets.  Note that this length is
 the actual length of the value, before any padding for alignment is
 added.
 TLV Value (variable):
 The TLV value field carries the data.  For extensibility, the TLV
 value may in fact be a TLV.  Padding is required when the length is
 not a multiple of 32 bits, and is the minimum number of octets
 required to bring the TLV to a multiple of 32 bits.  The length of
 the value before padding is indicated by the TLV Length field.

Doria, et al. Standards Track [Page 40] RFC 5810 ForCES March 2010

 Note: The value field could be empty, which implies the minimal
 length a TLV could be is 4 (length of "T" field and length of "L"
 field).

6.2.1. Nested TLVs

 TLV values can be other TLVs.  This provides the benefits of protocol
 flexibility (being able to add new extensions by introducing new TLVs
 when needed).  The nesting feature also allows for a conceptual
 optimization with the XML LFB definitions to binary PL representation
 (represented by nested TLVs).

6.2.2. Scope of the T in TLV

 There are two global name scopes for the "Type" in the TLV.  The
 first name scope is for OPER-TLVs and is defined in A.4 whereas the
 second name scope is outside OPER-TLVs and is defined in section A.2.

6.3. ILV

 The ILV is a slight variation of the TLV.  This sets the type ("T")
 to be a 32-bit local index that refers to a ForCES component ID
 (refer to Section 6.4.1).
 The ILV length field is a 4-octet integer, and includes the length of
 the ILV type (4 octets), ILV Length (4 octets), and the length of the
 ILV data found in the value field, in octets.  Note that, as in the
 case of the TLV, this length is the actual length of the value,
 before any padding for alignment is added.
  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                        Identifier                             |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                        Length                                 |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                        Value                                  |
 .                                                               .
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                     Figure 15: ILV Representation
 It should be noted that the "I" values are of local scope and are
 defined by the data declarations from the LFB definition.  Refer to
 Section 7.1.8 for discussions on usage of ILVs.

Doria, et al. Standards Track [Page 41] RFC 5810 ForCES March 2010

6.4. Important Protocol Encapsulations

 In this section, we review a few encapsulation concepts that are used
 by the ForCES protocol for its operations.
 We briefly re-introduce two concepts, paths, and keys, from the
 ForCES model [RFC5812] in order to provide context.  The reader is
 referred to [RFC5812] for a lot of the finer details.
 For readability reasons, we introduce the encapsulation schemes that
 are used to carry content in a protocol message, namely, FULLDATA-
 TLV, SPARSEDATA-TLV, and RESULT-TLV.

6.4.1. Paths

 The ForCES model [RFC5812] defines an XML-based language that allows
 for a formal definition of LFBs.  This is similar to the relationship
 between ASN.1 and SNMP MIB definition (MIB being analogous to the LFB
 and ASN.1 being analogous to the XML model language).  Any entity
 that the CE configures on an FE MUST be formally defined in an LFB.
 These entities could be scalars (e.g., a 32-bit IPv4 address) or
 vectors (such as a nexthop table).  Each entity within the LFB is
 given a numeric 32-bit identifier known as a "component id".  This
 scheme allows the component to be "addressed" in a protocol
 construct.
 These addressable entities could be hierarchical (e.g., a table
 column or a cell within a table row).  In order to address
 hierarchical data, the concept of a path is introduced by the model
 [RFC5812].  A path is a series of 32-bit component IDs that are
 typically presented in a dot-notation (e.g., 1.2.3.4).  Section 7
 formally defines how paths are used to reference data that is being
 encapsulated within a protocol message.

6.4.2. Keys

 The ForCES model [RFC5812] defines two ways to address table rows.
 The standard/common mechanism is to allow table rows to be referenced
 by a 32-bit index.  The secondary mechanism is via keys that allow
 for content addressing.  An example key is a multi-field content key
 that uses the IP address and prefix length to uniquely reference an
 IPv4 routing table row.  In essence, while the common scheme to
 address a table row is via its table index, a table row's path could
 be derived from a key.  The KEYINFO-TLV (Section 7) is used to carry
 the data that is used to do the lookup.

Doria, et al. Standards Track [Page 42] RFC 5810 ForCES March 2010

6.4.3. DATA TLVs

 Data from or to the FE is carried in two types of TLVs: FULLDATA-TLV
 and SPARSEDATA-TLV.  Responses to operations executed by the FE are
 carried in RESULT-TLVs.
 In FULLDATA-TLV, the data is encoded in such a way that a receiver of
 such data, by virtue of being armed with knowledge of the path and
 the LFB definition, can infer or correlate the TLV "Value" contents.
 This is essentially an optimization that helps reduce the amount of
 description required for the transported data in the protocol
 grammar.  Refer to Appendix C for an example of FULLDATA-TLVs.
 A number of operations in ForCES will need to reference optional data
 within larger structures.  The SPARSEDATA-TLV encoding is provided to
 make it easier to encapsulate optionally appearing data components.
 Refer to Appendix C for an example of SPARSEDATA-TLV.
 RESULT-TLVs carry responses back from the FE based on a config issued
 by the CE.  Refer to Appendix C for examples of RESULT-TLVs and
 Section 7.1.7 for layout.

6.4.4. Addressing LFB Entities

 Section 6.4.1 and Section 6.4.2 discuss how to target an entity
 within an LFB.  However, the addressing mechanism used requires that
 an LFB type and instance are selected first.  The LFB selector is
 used to select an LFB type and instance being targeted.  Section 7
 goes into more details; for our purpose, we illustrate this concept
 using Figure 16 below.  More examples of layouts can be found reading
 further into the text (example: Figure 22).

Doria, et al. Standards Track [Page 43] RFC 5810 ForCES March 2010

    main hdr (Message type: example "config")
     |
     |
     |
     +- T = LFBselect
            |
            +-- LFBCLASSID (unique per LFB defined)
            |
            |
            +-- LFBInstance  (runtime configuration)
            |
            +-- T = An operation TLV describes what we do to an entity
                |   //Refer to the OPER-TLV values enumerated below
                |   //the TLVs that can be used for operations
                |
                |
                +--+-- one or more path encodings to target an entity
                   | // Refer to the discussion on keys and paths
                   |
                   |
                   +-- The associated data, if any, for the entity
                      // Refer to discussion on FULL/SPARSE DATA TLVs
                     Figure 16: Entity Addressing

7. Protocol Construction

 A protocol layer PDU consists of a common header (defined in
 Section 6.1 ) and a message body.  The common header is followed by a
 message-type-specific message body.  Each message body is formed from
 one or more top-level TLVs.  A top-level TLV may contain one or more
 sub-TLVs; these sub-TLVs are described in this document as OPER-TLVs,
 because they describe an operation to be done.

Doria, et al. Standards Track [Page 44] RFC 5810 ForCES March 2010

 +-------------+---------------+---------------------+---------------+
 |   Message   | Top-Level TLV |     OPER-TLV(s)     |   Reference   |
 |     Name    |               |                     |               |
 +-------------+---------------+---------------------+---------------+
 | Association |  (LFBselect)* |        REPORT       | Section 7.5.1 |
 |    Setup    |               |                     |               |
 | Association | ASRresult-TLV |         none        | Section 7.5.2 |
 |    Setup    |               |                     |               |
 |   Response  |               |                     |               |
 | Association | ASTreason-TLV |         none        | Section 7.5.3 |
 |   Teardown  |               |                     |               |
 |    Config   |  (LFBselect)+ |  (SET | SET-PROP |  | Section 7.6.1 |
 |             |               |    DEL | COMMIT |   |               |
 |             |               |       TRCOMP)+      |               |
 |    Config   |  (LFBselect)+ |   (SET-RESPONSE |   | Section 7.6.2 |
 |   Response  |               | SET-PROP-RESPONSE | |               |
 |             |               |    DEL-RESPONSE |   |               |
 |             |               |  COMMIT-RESPONSE)+  |               |
 |    Query    |  (LFBselect)+ |  (GET | GET-PROP)+  | Section 7.7.1 |
 |    Query    |  (LFBselect)+ |   (GET-RESPONSE |   | Section 7.7.2 |
 |   Response  |               | GET-PROP-RESPONSE)+ |               |
 |    Event    |   LFBselect   |        REPORT       |  Section 7.8  |
 |   Notifi-   |               |                     |               |
 |    cation   |               |                     |               |
 |    Packet   |  REDIRECT-TLV |         none        |  Section 7.9  |
 |   Redirect  |               |                     |               |
 |  Heartbeat  |      none     |         none        |  Section 7.10 |
 +-------------+---------------+---------------------+---------------+
                                Table 1
 The different messages are illustrated in Table 1.  The different
 message type numerical values are defined in Appendix A.1.  All the
 TLV values are defined in Appendix A.2.
 An LFBselect TLV (refer to Section 7.1.5) contains the LFB Classid
 and LFB instance being referenced as well as the OPER-TLV(s) being
 applied to that reference.
 Each type of OPER-TLV is constrained as to how it describes the paths
 and selectors of interest.  The following BNF describes the basic
 structure of an OPER-TLV and Table 2 gives the details for each type.

Doria, et al. Standards Track [Page 45] RFC 5810 ForCES March 2010

     OPER-TLV := 1*PATH-DATA-TLV
     PATH-DATA-TLV := PATH  [DATA]
     PATH := flags IDcount IDs [SELECTOR]
     SELECTOR :=  KEYINFO-TLV
     DATA := FULLDATA-TLV / SPARSEDATA-TLV / RESULT-TLV /
             1*PATH-DATA-TLV
     KEYINFO-TLV := KeyID FULLDATA-TLV
     FULLDATA-TLV := encoded data component which may nest
                    further FULLDATA-TLVs
     SPARSEDATA-TLV := encoded data that may have optionally
                      appearing components
     RESULT-TLV := Holds result code and optional FULLDATA-TLV
                      Figure 17: BNF of OPER-TLV
 o  PATH-DATA-TLV identifies the exact component targeted and may have
    zero or more paths associated with it.  The last PATH-DATA-TLV in
    the case of nesting of paths via the DATA construct in the case of
    SET, SET-PROP requests, and GET-RESPONSE/GET-PROP-RESPONSE is
    terminated by encoded data or response in the form of either
    FULLDATA-TLV or SPARSEDATA-TLV or RESULT-TLV.
 o  PATH provides the path to the data being referenced.
  • flags (16 bits) are used to further refine the operation to be

applied on the path. More on these later.

  • IDcount (16 bits): count of 32-bit IDs
  • IDs: zero or more 32-bit IDs (whose count is given by IDcount)

defining the main path. Depending on the flags, IDs could be

       field IDs only or a mix of field and dynamic IDs.  Zero is used
       for the special case of using the entirety of the containing
       context as the result of the path.
 o  SELECTOR is an optional construct that further defines the PATH.
    Currently, the only defined selector is the KEYINFO-TLV, used for
    selecting an array entry by the value of a key field.  The
    presence of a SELECTOR is correct only when the flags also
    indicate its presence.
 o  A KEYINFO-TLV contains information used in content keying.
  • A 32-bit KeyID is used in a KEYINFO-TLV. It indicates which

key for the current array is being used as the content key for

       array entry selection.

Doria, et al. Standards Track [Page 46] RFC 5810 ForCES March 2010

  • The key's data is the data to look for in the array, in the

fields identified by the key field. The information is encoded

       according to the rules for the contents of a FULLDATA-TLV, and
       represents the field or fields that make up the key identified
       by the KeyID.
 o  DATA may contain a FULLDATA-TLV, SPARSEDATA-TLV, a RESULT-TLV, or
    1 or more further PATH-DATA selections.  FULLDATA-TLV and
    SPARSEDATA-TLV are only allowed on SET or SET-PROP requests, or on
    responses that return content information (GET-RESPONSE, for
    example).  PATH-DATA may be included to extend the path on any
    request.
  • Note: Nested PATH-DATA-TLVs are supported as an efficiency

measure to permit common subexpression extraction.

  • FULLDATA-TLV and SPARSEDATA-TLV contain "the data" whose path

has been selected by the PATH. Refer to Section 7.1 for

       details.
  • The following table summarizes the applicability and

restrictions of the FULL/SPARSEDATA-TLVs and the RESULT-TLV to

       the OPER-TLVs.
 +-------------------+-------------------------------+---------------+
 |      OPER-TLV     |            DATA TLV           |   RESULT-TLV  |
 +-------------------+-------------------------------+---------------+
 |        SET        |                               |      none     |
 |      SET-PROP     |        (FULLDATA-TLV |        |      none     |
 |                   |        SPARSEDATA-TLV)+       |               |
 |    SET-RESPONSE   |              none             | (RESULT-TLV)+ |
 | SET-PROP-RESPONSE |              none             | (RESULT-TLV)+ |
 |        DEL        |                               |      none     |
 |    DEL-RESPONSE   |              none             | (RESULT-TLV)+ |
 |        GET        |              none             |      none     |
 |      GET-PROP     |              none             |      none     |
 |    GET-RESPONSE   |        (FULLDATA-TLV)+        | (RESULT-TLV)* |
 | GET-PROP-RESPONSE |        (FULLDATA-TLV)+        | (RESULT-TLV)* |
 |       REPORT      |        (FULLDATA-TLV)+        |      none     |
 |       COMMIT      |              none             |      none     |
 |  COMMIT-RESPONSE  |              none             | (RESULT-TLV)+ |
 |       TRCOMP      |              none             |      none     |
 +-------------------+-------------------------------+---------------+
                                   Table 2

Doria, et al. Standards Track [Page 47] RFC 5810 ForCES March 2010

 o  RESULT-TLV contains the indication of whether the individual SET
    or SET-PROP succeeded.  RESULT-TLV is included on the assumption
    that individual parts of a SET request can succeed or fail
    separately.
 In summary, this approach has the following characteristics:
 o  There can be one or more LFB class ID and instance ID combinations
    targeted in a message (batch).
 o  There can one or more operations on an addressed LFB class ID/
    instance ID combination (batch).
 o  There can be one or more path targets per operation (batch).
 o  Paths may have zero or more data values associated (flexibility
    and operation specific).
 It should be noted that the above is optimized for the case of a
 single LFB class ID and instance ID targeting.  To target multiple
 instances within the same class, multiple LFBselects are needed.

7.1. Discussion on Encoding

 Section 6.4.3 discusses the two types of DATA encodings (FULLDATA-TLV
 and SPARSEDATA-TLV) and the justifications for their existence.  In
 this section, we explain how they are encoded.

7.1.1. Data Packing Rules

 The scheme for encoding data used in this document adheres to the
 following rules:
 o  The Value ("V" of TLV) of FULLDATA-TLV will contain the data being
    transported.  This data will be as was described in the LFB
    definition.
 o  Variable-sized data within a FULLDATA-TLV will be encapsulated
    inside another FULLDATA-TLV inside the V of the outer TLV.  For an
    example of such a setup, refer to Appendices C and D.
 o  In the case of FULLDATA-TLVs:
  • When a table is referred to in the PATH (IDs) of a PATH-DATA-

TLV, then the FULLDATA-TLV's "V" will contain that table's row

       content prefixed by its 32-bit index/subscript.  On the other

Doria, et al. Standards Track [Page 48] RFC 5810 ForCES March 2010

       hand, the PATH may contain an index pointing to a row in table;
       in such a case, the FULLDATA-TLV's "V" will only contain the
       content with the index in order to avoid ambiguity.

7.1.2. Path Flags

 Only bit 0, the SELECTOR Bit, is currently used in the path flags as
 illustrated in Figure 18.
    0                   1
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | |                           |
    |S|   Reserved                |
    | |                           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    Figure 18: Path Flags
    The semantics of the flag are defined as follows:
 o  SELECTOR Bit: F_SELKEY(set to 1) indicates that a KEY Selector is
    present following this path information, and should be considered
    in evaluating the path content.

7.1.3. Relation of Operational Flags with Global Message Flags

 Global flags, such as the execution mode and the atomicity indicators
 defined in the header, apply to all operations in a message.  Global
 flags provide semantics that are orthogonal to those provided by the
 operational flags, such as the flags defined in path-data.  The scope
 of operational flags is restricted to the operation.

7.1.4. Content Path Selection

 The KEYINFO-TLV describes the KEY as well as associated KEY data.
 KEYs, used for content searches, are restricted and described in the
 LFB definition.

7.1.5. LFBselect-TLV

 The LFBselect TLV is an instance of a TLV as defined in Section 6.2.
 The definition is as follows:

Doria, et al. Standards Track [Page 49] RFC 5810 ForCES March 2010

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |        Type = LFBselect       |               Length          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                          LFB Class ID                         |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        LFB Instance ID                        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        OPER-TLV                               |
  .                                                               .
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  ~                           ...                                 ~
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        OPER-TLV                               |
  .                                                               .
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                       Figure 19: PL PDU Layout
 Type:
 The type of the TLV is "LFBselect"
 Length:
 Length of the TLV including the T and L fields, in octets.
 LFB Class ID:
 This field uniquely recognizes the LFB class/type.
 LFB Instance ID:
 This field uniquely identifies the LFB instance.
 OPER-TLV:
 It describes an operation nested in the LFBselect TLV.  Note that
 usually there SHOULD be at least one OPER-TLV present for an LFB
 select TLV.

7.1.6. OPER-TLV

 The OPER-TLV is a place holder in the grammar for TLVs that define
 operations.  The different types are defined in Table 3, below.

Doria, et al. Standards Track [Page 50] RFC 5810 ForCES March 2010

 +-------------------+--------+--------------------------------------+
 |      OPER-TLV     |   TLV  |               Comments               |
 |                   | "Type" |                                      |
 +-------------------+--------+--------------------------------------+
 |        SET        | 0x0001 |   From CE to FE.  Used to create or  |
 |                   |        |       add or update components       |
 |      SET-PROP     | 0x0002 |   From CE to FE.  Used to create or  |
 |                   |        |  add or update component properties  |
 |    SET-RESPONSE   | 0x0003 |     From FE to CE.  Used to carry    |
 |                   |        |           response of a SET          |
 | SET-PROP-RESPONSE | 0x0004 |     From FE to CE.  Used to carry    |
 |                   |        |        response of a SET-PROP        |
 |        DEL        | 0x0005 |   From CE to FE.  Used to delete or  |
 |                   |        |          remove an component         |
 |    DEL-RESPONSE   | 0x0006 |     From FE to CE.  Used to carry    |
 |                   |        |           response of a DEL          |
 |        GET        | 0x0007 |  From CE to FE.  Used to retrieve an |
 |                   |        |               component              |
 |      GET-PROP     | 0x0008 |  From CE to FE.  Used to retrieve an |
 |                   |        |          component property          |
 |    GET-RESPONSE   | 0x0009 |     From FE to CE.  Used to carry    |
 |                   |        |           response of a GET          |
 | GET-PROP-RESPONSE | 0x000A |     From FE to CE.  Used to carry    |
 |                   |        |        response of a GET-PROP        |
 |       REPORT      | 0x000B |   From FE to CE.  Used to carry an   |
 |                   |        |          asynchronous event          |
 |       COMMIT      | 0x000C |    From CE to FE.  Used to issue a   |
 |                   |        |      commit in a 2PC transaction     |
 |  COMMIT-RESPONSE  | 0x000D |   From FE to CE.  Used to confirm a  |
 |                   |        |      commit in a 2PC transaction     |
 |       TRCOMP      | 0x000E |   From CE to FE.  Used to indicate   |
 |                   |        |  NE-wide success of 2PC transaction  |
 +-------------------+--------+--------------------------------------+
                                Table 3
 Different messages use OPER-TLV and define how they are used (refer
 to Table 1 and Table 2).
 SET, SET-PROP, and GET/GET-PROP requests are issued by the CE and do
 not carry RESULT-TLVs.  On the other hand, SET-RESPONSE, SET-PROP-
 RESPONSE, and GET-RESPONSE/GET-PROP-RESPONSE carry RESULT-TLVs.
 A GET-RESPONSE in response to a successful GET will have FULLDATA-
 TLVs added to the leaf paths to carry the requested data.  For GET
 operations that fail, instead of the FULLDATA-TLV there will be a
 RESULT-TLV.

Doria, et al. Standards Track [Page 51] RFC 5810 ForCES March 2010

 For a SET-RESPONSE/SET-PROP-RESPONSE, each FULLDATA-TLV or
 SPARSEDATA-TLV in the original request will be replaced with a
 RESULT-TLV in the response.  If the request set the FailureACK flag,
 then only those items that failed will appear in the response.  If
 the request was for AlwaysACK, then all components of the request
 will appear in the response with RESULT-TLVs.
 Note that if a SET/SET-PROP request with a structure in a FULLDATA-
 TLV is issued, and some field in the structure is invalid, the FE
 will not attempt to indicate which field was invalid, but rather will
 indicate that the operation failed.  Note further that if there are
 multiple errors in a single leaf PATH-DATA/FULLDATA-TLB, the FE can
 select which error it chooses to return.  So if a FULLDATA-TLV for a
 SET/SET-PROP of a structure attempts to write one field that is read
 only, and attempts to set another field to an invalid value, the FE
 can return indication of either error.
 A SET/SET-PROP operation on a variable-length component with a length
 of 0 for the item is not the same as deleting it.  If the CE wishes
 to delete, then the DEL operation should be used whether the path
 refers to an array component or an optional structure component.

7.1.7. RESULT TLV

 The RESULT-TLV is an instance of TLV defined in Section 6.2.  The
 definition is as follows:
      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    Type = RESULT-TLV          |               Length          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Result Value  |                  Reserved                     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         Figure 20: RESULT-TLV

Doria, et al. Standards Track [Page 52] RFC 5810 ForCES March 2010

                         Defined Result Values
 +-----------------------------+-----------+-------------------------+
 |         Result Value        |   Value   |        Definition       |
 +-----------------------------+-----------+-------------------------+
 |          E_SUCCESS          |    0x00   |         Success         |
 |       E_INVALID_HEADER      |    0x01   |  Unspecified error with |
 |                             |           |         header.         |
 |      E_LENGTH_MISMATCH      |    0x02   |   Header length field   |
 |                             |           |  does not match actual  |
 |                             |           |      packet length.     |
 |      E_VERSION_MISMATCH     |    0x03   |  Unresolvable mismatch  |
 |                             |           |       in versions.      |
 |  E_INVALID_DESTINATION_PID  |    0x04   |    Destination PID is   |
 |                             |           | invalid for the message |
 |                             |           |        receiver.        |
 |        E_LFB_UNKNOWN        |    0x05   |   LFB Class ID is not   |
 |                             |           |    known by receiver.   |
 |       E_LFB_NOT_FOUND       |    0x06   |  LFB Class ID is known  |
 |                             |           |   by receiver but not   |
 |                             |           |    currently in use.    |
 | E_LFB_INSTANCE_ID_NOT_FOUND |    0x07   |  LFB Class ID is known  |
 |                             |           |    but the specified    |
 |                             |           |  instance of that class |
 |                             |           |     does not exist.     |
 |        E_INVALID_PATH       |    0x08   |  The specified path is  |
 |                             |           |       impossible.       |
 |  E_COMPONENT_DOES_NOT_EXIST |    0x09   |  The specified path is  |
 |                             |           |     possible but the    |
 |                             |           |    component does not   |
 |                             |           | exist (e.g., attempt to |
 |                             |           | modify a table row that |
 |                             |           |  has not been created). |
 |           E_EXISTS          |    0x0A   |   The specified object  |
 |                             |           |   exists but it cannot  |
 |                             |           | exist for the operation |
 |                             |           |    to succeed (e.g.,    |
 |                             |           |    attempt to add an    |
 |                             |           |  existing LFB instance  |
 |                             |           |   or array subscript).  |
 |         E_NOT_FOUND         |    0x0B   |   The specified object  |
 |                             |           |  does not exist but it  |
 |                             |           |    MUST exist for the   |
 |                             |           |   operation to succeed  |
 |                             |           |    (e.g., attempt to    |
 |                             |           |  delete a non-existing  |
 |                             |           |  LFB instance or array  |
 |                             |           |       subscript).       |

Doria, et al. Standards Track [Page 53] RFC 5810 ForCES March 2010

 |         E_READ_ONLY         |    0x0C   |   Attempt to modify a   |
 |                             |           |     read-only value.    |
 |   E_INVALID_ARRAY_CREATION  |    0x0D   |   Attempt to create an  |
 |                             |           | array with an unallowed |
 |                             |           |        subscript.       |
 |     E_VALUE_OUT_OF_RANGE    |    0x0E   |     Attempt to set a    |
 |                             |           |   parameter to a value  |
 |                             |           |      outside of its     |
 |                             |           |     allowable range.    |
 |     E_CONTENTS_TOO_LONG     |    0x0D   |     Attempt to write    |
 |                             |           |   contents larger than  |
 |                             |           | the target object space |
 |                             |           |    (i.e., exceeding a   |
 |                             |           |         buffer).        |
 |     E_INVALID_PARAMETERS    |    0x10   |   Any other error with  |
 |                             |           |     data parameters.    |
 |    E_INVALID_MESSAGE_TYPE   |    0x11   |   Message type is not   |
 |                             |           |       acceptable.       |
 |       E_INVALID_FLAGS       |    0x12   |  Message flags are not  |
 |                             |           |    acceptable for the   |
 |                             |           |   given message type.   |
 |        E_INVALID_TLV        |    0x13   | A TLV is not acceptable |
 |                             |           |  for the given message  |
 |                             |           |          type.          |
 |        E_EVENT_ERROR        |    0x14   | Unspecified error while |
 |                             |           |    handling an event.   |
 |       E_NOT_SUPPORTED       |    0x15   |   Attempt to perform a  |
 |                             |           |  valid ForCES operation |
 |                             |           |  that is unsupported by |
 |                             |           |  the message receiver.  |
 |        E_MEMORY_ERROR       |    0x16   | A memory error occurred |
 |                             |           |    while processing a   |
 |                             |           |    message (no error    |
 |                             |           | detected in the message |
 |                             |           |         itself).        |
 |       E_INTERNAL_ERROR      |    0x17   |   An unspecified error  |
 |                             |           |      occurred while     |
 |                             |           |   processing a message  |
 |                             |           |  (no error detected in  |
 |                             |           |   the message itself).  |
 |              -              | 0x18-0xFE |         Reserved        |
 |     E_UNSPECIFIED_ERROR     |    0xFF   |  Unspecified error (for |
 |                             |           |    when the FE cannot   |
 |                             |           |     decide what went    |
 |                             |           |         wrong).         |
 +-----------------------------+-----------+-------------------------+
                                Table 4

Doria, et al. Standards Track [Page 54] RFC 5810 ForCES March 2010

7.1.8. DATA TLV

 A FULLDATA-TLV has "T"= FULLDATA-TLV and a 16-bit length followed by
 the data value/contents.  Likewise, a SPARSEDATA-TLV has "T" =
 SPARSEDATA-TLV, a 16-bit length, followed by the data value/contents.
 In the case of the SPARSEDATA-TLV, each component in the Value part
 of the TLV will be further encapsulated in an ILV.
 Below are the encoding rules for the FULLDATA-TLV and SPARSEDATA-
 TLVs.  Appendix C is very useful in illustrating these rules:
 1.  Both ILVs and TLVs MUST be 32-bit aligned.  Any padding bits used
     for the alignment MUST be zero on transmission and MUST be
     ignored upon reception.
 2.  FULLDATA-TLVs may be used at a particular path only if every
     component at that path level is present.  In example 1(c) of
     Appendix C, this concept is illustrated by the presence of all
     components of the structure S in the FULLDATA-TLV encoding.  This
     requirement holds regardless of whether the fields are fixed or
     variable length, mandatory or optional.
  • If a FULLDATA-TLV is used, the encoder MUST lay out data for

each component in the same order in which the data was

         defined in the LFB specification.  This ensures the decoder
         is able to retrieve the data.  To use the example 1 again in
         Appendix C, this implies the encoder/decoder is assumed to
         have knowledge of how structure S is laid out in the
         definition.
  • In the case of a SPARSEDATA-TLV, it does not need to be

ordered since the "I" in the ILV uniquely identifies the

         component.  Examples 1(a) and 1(b) in Appendix C illustrate
         the power of SPARSEDATA-TLV encoding.
 3.  Inside a FULLDATA-TLV
  • The values for atomic, fixed-length fields are given without

any TLV encapsulation.

  • The values for atomic, variable-length fields are given

inside FULLDATA-TLVs.

  • The values for arrays are in the form of index/subscript,

followed by value as stated in "Data Packing Rules"

         (Section 7.1.1) and demonstrated by the examples in the
         appendices.

Doria, et al. Standards Track [Page 55] RFC 5810 ForCES March 2010

 4.  Inside a SPARSEDATA-TLV
  • The values of all fields MUST be given with ILVs (32-bit

index, 32-bit length).

 5.  FULLDATA-TLVs cannot contain an ILV.
 6.  A FULLDATA-TLV can also contain a FULLDATA-TLV for variable-sized
     components.  The decoding disambiguation is assumed from rule #3
     above.

7.1.9. SET and GET Relationship

 It is expected that a GET-RESPONSE would satisfy the following:
 o   It would have exactly the same path definitions as those sent in
     the GET.  The only difference is that a GET-RESPONSE will contain
     FULLDATA-TLVs.
 o   It should be possible to take the same GET-RESPONSE and convert
     it to a SET successfully by merely changing the T in the
     operational TLV.
 o   There are exceptions to this rule:
     1.  When a KEY selector is used with a path in a GET operation,
         that selector is not returned in the GET-RESPONSE; instead,
         the cooked result is returned.  Refer to the examples using
         KEYS to see this.
     2.  When dumping a whole table in a GET, the GET-RESPONSE that
         merely edits the T to be SET will end up overwriting the
         table.

7.2. Protocol Encoding Visualization

 The figure below shows a general layout of the PL PDU.  A main header
 is followed by one or more LFB selections each of which may contain
 one or more operations.

Doria, et al. Standards Track [Page 56] RFC 5810 ForCES March 2010

 main hdr (Config in this case)
      |
      |
      +--- T = LFBselect
      |        |
      |        +-- LFBCLASSID
      |        |
      |        |
      |        +-- LFBInstance
      |        |
      |        +-- T = SET
      |        |   |
      |        |   +--  // one or more path targets
      |        |        // with their data here to be added
      |        |
      |        +-- T  = DEL
      |        .   |
      |        .   +--  // one or more path targets to be deleted
      |
      |
      +--- T = LFBselect
      |        |
      |        +-- LFBCLASSID
      |        |
      |        |
      |        +-- LFBInstance
      |        |
      |        + -- T= SET
      |        |    .
      |        |    .
      |        + -- T= DEL
      |        |    .
      |        |    .
      |        |
      |        + -- T= SET
      |        |    .
      |        |    .
      |
      |
      +--- T = LFBselect
              |
              +-- LFBCLASSID
              |
              +-- LFBInstance
              .
              .
              .
                   Figure 21: PL PDU Logical Layout

Doria, et al. Standards Track [Page 57] RFC 5810 ForCES March 2010

 The figure below shows a more detailed example of the general layout
 of the operation within a targeted LFB selection.  The idea is to
 show the different nesting levels a path could take to get to the
 target path.
      T = SET
      |  |
      |  +- T = Path-data
      |       |
      |       + -- flags
      |       + -- IDCount
      |       + -- IDs
      |       |
      |       +- T = Path-data
      |          |
      |          + -- flags
      |          + -- IDCount
      |          + -- IDs
      |          |
      |          +- T = Path-data
      |             |
      |             + -- flags
      |             + -- IDCount
      |             + -- IDs
      |             + -- T = KEYINFO-TLV
      |             |    + -- KEY_ID
      |             |    + -- KEY_DATA
      |             |
      |             + -- T = FULLDATA-TLV
      |                  + -- data
      |
      |
      T = SET
      |  |
      |  +- T = Path-data
      |  |  |
      |  |  + -- flags
      |  |  + -- IDCount
      |  |  + -- IDs
      |  |  |
      |  |  + -- T = FULLDATA-TLV
      |  |          + -- data
      |  +- T = Path-data
      |     |

Doria, et al. Standards Track [Page 58] RFC 5810 ForCES March 2010

      |     + -- flags
      |     + -- IDCount
      |     + -- IDs
      |     |
      |     + -- T = FULLDATA-TLV
      |             + -- data
      T = DEL
         |
         +- T = Path-data
              |
              + -- flags
              + -- IDCount
              + -- IDs
              |
              +- T = Path-data
                 |
                 + -- flags
                 + -- IDCount
                 + -- IDs
                 |
                 +- T = Path-data
                    |
                    + -- flags
                    + -- IDCount
                    + -- IDs
                    + -- T = KEYINFO-TLV
                    |    + -- KEY_ID
                    |    + -- KEY_DATA
                    +- T = Path-data
                         |
                         + -- flags
                         + -- IDCount
                         + -- IDs
                  Figure 22: Sample Operation Layout
 Appendix D shows a more concise set of use cases on how the data
 encoding is done.

7.3. Core ForCES LFBs

 There are two LFBs that are used to control the operation of the
 ForCES protocol and to interact with FEs and CEs:
 o  FE Protocol LFB

Doria, et al. Standards Track [Page 59] RFC 5810 ForCES March 2010

 o  FE Object LFB
 Although these LFBs have the same form and interface as other LFBs,
 they are special in many respects.  They have fixed well-known LFB
 Class and Instance IDs.  They are statically defined (no dynamic
 instantiation allowed), and their status cannot be changed by the
 protocol: any operation to change the state of such LFBs (for
 instance, in order to disable the LFB) MUST result in an error.
 Moreover, these LFBs MUST exist before the first ForCES message can
 be sent or received.  All components in these LFBs MUST have pre-
 defined default values.  Finally, these LFBs do not have input or
 output ports and do not integrate into the intra-FE LFB topology.

7.3.1. FE Protocol LFB

 The FE Protocol LFB is a logical entity in each FE that is used to
 control the ForCES protocol.  The FE Protocol LFB Class ID is
 assigned the value 0x2.  The FE Protocol LFB Instance ID is assigned
 the value 0x1.  There MUST be one and only one instance of the FE
 Protocol LFB in an FE.  The values of the components in the FE
 Protocol LFB have pre-defined default values that are specified here.
 Unless explicit changes are made to these values using Config
 messages from the CE, these default values MUST be used for correct
 operation of the protocol.
 The formal definition of the FE Protocol Object LFB can be found in
 Appendix B.

7.3.1.1. FE Protocol Capabilities

 FE Protocol capabilities are read-only.

7.3.1.1.1. SupportableVersions

 ForCES protocol version(s) supported by the FE.

7.3.1.1.2. FE Protocol Components

 FE Protocol components (can be read and set).

7.3.1.1.2.1. CurrentRunningVersion

 Current running version of the ForCES protocol.

Doria, et al. Standards Track [Page 60] RFC 5810 ForCES March 2010

7.3.1.1.2.2. FEID

 FE unicast ID.

7.3.1.1.2.3. MulticastFEIDs

 FE multicast ID(s) list - This is a list of multicast IDs to which
 the FE belongs.  These IDs are configured by the CE.

7.3.1.1.2.4. CEHBPolicy

 CE heartbeat policy - This policy, along with the parameter 'CE
 Heartbeat Dead Interval (CE HDI)' as described below, defines the
 operating parameters for the FE to check the CE liveness.  The policy
 values with meanings are listed as follows:
 o  0 (default) - This policy specifies that the CE will send a
    Heartbeat message to the FE(s) whenever the CE reaches a time
    interval within which no other PL messages were sent from the CE
    to the FE(s); refer to Section 4.3.3 and Section 7.10 for details.
    The CE HDI component as described below is tied to this policy.
 o  1 - The CE will not generate any HB messages.  This actually means
    that the CE does not want the FE to check the CE liveness.
 o  Others - Reserved.

7.3.1.1.2.5. CEHDI

 CE Heartbeat Dead Interval (CE HDI) - The time interval the FE uses
 to check the CE liveness.  If FE has not received any messages from
 CE within this time interval, FE deduces lost connectivity, which
 implies that the CE is dead or the association to the CE is lost.
 Default value is 30 s.

7.3.1.1.2.6. FEHBPolicy

 FE heartbeat policy - This policy, along with the parameter 'FE
 Heartbeat Interval (FE HI)', defines the operating parameters for how
 the FE should behave so that the CE can deduce its liveness.  The
 policy values and the meanings are:
 o  0 (default) - The FE should not generate any Heartbeat messages.
    In this scenario, the CE is responsible for checking FE liveness
    by setting the PL header ACK flag of the message it sends to
    AlwaysACK.  The FE responds to the CE whenever the CE sends such
    Heartbeat Request messages.  Refer to Section 7.10 and
    Section 4.3.3 for details.

Doria, et al. Standards Track [Page 61] RFC 5810 ForCES March 2010

 o  1 - This policy specifies that the FE MUST actively send a
    Heartbeat message if it reaches the time interval assigned by the
    FE HI as long as no other messages were sent from the FE to the CE
    during that interval as described in Section 4.3.3.
 o  Others - Reserved.

7.3.1.1.2.7. FEHI

 FE Heartbeat Interval (FE HI) - The time interval the FE should use
 to send HB as long as no other messages were sent from the FE to the
 CE during that interval as described in Section 4.3.3.  The default
 value for an FE HI is 500 ms.

7.3.1.1.2.8. CEID

 Primary CEID - The CEID with which the FE is associated.

7.3.1.1.2.9. LastCEID

 Last Primary CEID - The CEID of the last CE with which the FE
 associated.  This CE ID is reported to the new Primary CEID.

7.3.1.1.2.10. BackupCEs

 The list of backup CEs an FE can use as backups.  Refer to Section 8
 for details.

7.3.1.1.2.11. CEFailoverPolicy

 CE failover policy - This specifies the behavior of the FE when the
 association with the CE is lost.  There is a very tight relation
 between CE failover policy and Section 7.3.1.1.2.8,
 Section 7.3.1.1.2.10, Section 7.3.1.1.2.12, and Section 8.  When an
 association is lost, depending on configuration, one of the policies
 listed below is activated.
 o  0 (default) - The FE should stop functioning immediately and
    transition to FE OperDisable.
 o  1 - The FE should continue running and do what it can even without
    an associated CE.  This basically requires that the FE support CE
    Graceful restart (and defines such support in its capabilities).
    If the CEFTI expires before the FE re-associates with either the
    primary CEID (Section 7.3.1.1.2.8) or one of possibly several
    backup CEs (Section 7.3.1.1.2.10), the FE will go operationally
    down.

Doria, et al. Standards Track [Page 62] RFC 5810 ForCES March 2010

 o  Others - Reserved.

7.3.1.1.2.12. CEFTI

 CE Failover Timeout Interval (CEFTI) - The time interval associated
 with the CE failover policy case '0' and '1'.  The default value is
 set to 300 seconds.  Note that it is advisable to set the CEFTI value
 much higher than the CE Heartbeat Dead Interval (CE HDI) since the
 effect of expiring this parameter is devastating to the operation of
 the FE.

7.3.1.1.2.13. FERestartPolicy

 FE restart policy - This specifies the behavior of the FE during an
 FE restart.  The restart may be from an FE failure or other reasons
 that have made the FE down and then need to restart.  The values are
 defined as follows:
 o  0(default)- Restart the FE from scratch.  In this case, the FE
    should start from the pre-association phase.
 o  Others - Reserved for future use.

7.3.2. FE Object LFB

 The FE Object LFB is a logical entity in each FE and contains
 components relative to the FE itself, and not to the operation of the
 ForCES protocol.
 The formal definition of the FE Object LFB can be found in [RFC5812].
 The model captures the high-level properties of the FE that the CE
 needs to know to begin working with the FE.  The class ID for this
 LFB class is also assigned in [RFC5812].  The singular instance of
 this class will always exist, and will always have instance ID 0x1
 within its class.  It is common, although not mandatory, for a CE to
 fetch much of the component and capability information from this LFB
 instance when the CE begins controlling the operation of the FE.

7.4. Semantics of Message Direction

 Recall: The PL provides a master(CE)-slave(FE) relationship.  The
 LFBs reside at the FE and are controlled by CE.
 When messages go from the CE, the LFB selector (class and instance)
 refers to the destination LFB selection that resides in the FE.
 When messages go from the FE to the CE, the LFB selector (class and
 instance) refers to the source LFB selection that resides in the FE.

Doria, et al. Standards Track [Page 63] RFC 5810 ForCES March 2010

7.5. Association Messages

 The ForCES Association messages are used to establish and tear down
 associations between FEs and CEs.

7.5.1. Association Setup Message

 This message is sent by the FE to the CE to set up a ForCES
 association between them.
 Message transfer direction:
    FE to CE
 Message header:
    The Message Type in the header is set to MessageType=
    'AssociationSetup'.  The ACK flag in the header MUST be ignored,
    and the Association Setup message always expects to get a response
    from the message receiver (CE), whether or not the setup is
    successful.  The correlator field in the header is set, so that FE
    can correlate the response coming back from the CE correctly.  The
    FE may set the source ID to 0 in the header to request that the CE
    should assign an FE ID for the FE in the Setup Response message.
 Message body:
    The Association Setup message body optionally consists of zero,
    one, or two LFBselect TLVs, as described in Section 7.1.5.  The
    Association Setup message only operates on the FE Object and FE
    Protocol LFBs; therefore, the LFB class ID in the LFBselect TLV
    only points to these two kinds of LFBs.
    The OPER-TLV in the LFBselect TLV is defined as a 'REPORT'
    operation.  More than one component may be announced in this
    message using the REPORT operation to let the FE declare its
    configuration parameters in an unsolicited manner.  These may
    contain components suggesting values such as the FE HB Interval or
    the FEID.  The OPER-TLV used is defined below.

Doria, et al. Standards Track [Page 64] RFC 5810 ForCES March 2010

 OPER-TLV for Association Setup:
   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |    Type = REPORT              |               Length          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                    PATH-DATA-TLV for REPORT                   |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                           Figure 23: OPER-TLV
 Type:
    Only one operation type is defined for the Association Setup
    message:
    Type = "REPORT" - This type of operation is for the FE to report
           something to the CE.
 PATH-DATA-TLV for REPORT:
    This is generically a PATH-DATA-TLV format that has been defined
    in Section 7 in the PATH-DATA BNF definition.  The PATH-DATA-TLV
    for the REPORT operation MAY contain FULLDATA-TLV(s) but SHALL NOT
    contain any RESULT-TLV in the data format.  The RESULT-TLV is
    defined in Section 7.1.7 and the FULLDATA-TLV is defined in
    Section 7.1.8.

Doria, et al. Standards Track [Page 65] RFC 5810 ForCES March 2010

 To better illustrate the above PDU format, a tree structure for the
 format is shown below:
 main hdr (type =  Association Setup)
      |
      |
      +--- T = LFBselect
      |        |
      |        +-- LFBCLASSID = FE object
      |        |
      |        |
      |        +-- LFBInstance = 0x1
      |
      +--- T = LFBselect
               |
               +-- LFBCLASSID = FE Protocol object
               |
               |
               +-- LFBInstance = 0x1
                     |
                     +---OPER-TLV = REPORT
                         |
                         +-- Path-data to one or more components
          Figure 24: PDU Format for Association Setup Message

7.5.2. Association Setup Response Message

 This message is sent by the CE to the FE in response to the Setup
 message.  It indicates to the FE whether or not the setup is
 successful, i.e., whether an association is established.
 Message transfer direction:
 CE to FE
 Message header:
 The Message Type in the header is set to MessageType=
 'AssociationSetupResponse'.  The ACK flag in the header MUST be
 ignored, and the Setup Response message never expects to get any more
 responses from the message receiver (FE).  The destination ID in the
 header will be set to the source ID in the corresponding Association
 Setup message, unless that source ID was 0.  If the corresponding
 source ID was 0, then the CE will assign an FE ID value and use that
 value for the destination ID.

Doria, et al. Standards Track [Page 66] RFC 5810 ForCES March 2010

  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |        Type = ASRresult       |               Length          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                  Association Setup Result                     |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                       Figure 25: ASResult OPER-TLV
 Type (16 bits):
 The type of the TLV is "ASResult".
 Length (16 bits):
 Length of the TLV including the T and L fields, in octets.
 Association Setup result (32 bits):
 This indicates whether the Setup message was successful or whether
 the FE request was rejected by the CE.  The defined values are:
     0 = success
     1 = FE ID invalid
     2 = permission denied

Doria, et al. Standards Track [Page 67] RFC 5810 ForCES March 2010

 To better illustrate the above PDU format, a tree structure for the
 format is shown below:
 main hdr (type =  Association Setup Response)
  |
  |
  +--- T = ASResult-TLV
    Figure 26: PDU Format for Association Setup Response Message

7.5.3. Association Teardown Message

 This message can be sent by the FE or CE to any ForCES element to end
 its ForCES association with that element.
 Message transfer direction:
 CE to FE, or FE to CE (or CE to CE)
 Message Header:
 The Message Type in the header is set to MessageType=
 "AssociationTeardown".  The ACK flag MUST be ignored.  The correlator
 field in the header MUST be set to zero and MUST be ignored by the
 receiver.
   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |        Type = ASTreason       |               Length          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                      Teardown Reason                          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         Figure 27: ASTreason-TLV
 Type (16 bits):
 The type of the TLV is "ASTreason".
 Length (16 bits):
 Length of the TLV including the T and L fields, in octets.
 Teardown reason (32 bits):
 This indicates the reason why the association is being terminated.
 Several reason codes are defined as follows.

Doria, et al. Standards Track [Page 68] RFC 5810 ForCES March 2010

     0 - normal teardown by administrator
     1 - error - loss of heartbeats
     2 - error - out of bandwidth
     3 - error - out of memory
     4 - error - application crash
     255 - error - other or unspecified
 To better illustrate the above PDU format, a tree structure for the
 format is shown below:
 main hdr (type =  Association Teardown)
  |
  |
  +--- T = ASTreason-TLV
    Figure 28: PDU Format for Association Teardown Message

7.6. Configuration Messages

 The ForCES Configuration messages are used by CE to configure the FEs
 in a ForCES NE and report the results back to the CE.

7.6.1. Config Message

 This message is sent by the CE to the FE to configure LFB components
 in the FE.  This message is also used by the CE to subscribe/
 unsubscribe to LFB events.
 As usual, a Config message is composed of a common header followed by
 a message body that consists of one or more TLV data formats.
 Detailed description of the message is as follows:
 Message transfer direction:
 CE to FE
 Message header:
 The Message Type in the header is set to MessageType= 'Config'.  The
 ACK flag in the header can be set to any value defined in
 Section 6.1, to indicate whether or not a response from the FE is
 expected by the message.

Doria, et al. Standards Track [Page 69] RFC 5810 ForCES March 2010

 OPER-TLV for Config:
   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Type                 |               Length          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        PATH-DATA-TLV                          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                      Figure 29: OPER-TLV for Config
 Type:
 The operation type for Config message.  Two types of operations for
 the Config message are defined:
     Type = "SET" - This operation is to set LFB components
     Type = "SET-PROP" - This operation is to set LFB component
            properties.
     Type = "DEL" - This operation is to delete some LFB components.
     Type = "COMMIT" - This operation is sent to the FE to commit in a
            2pc transaction.  A COMMIT TLV is an empty TLV, i.e., it
            has no "V"alue.  In other words, there is a length of 4
            (which is for the header only).
     Type = "TRCOMP" - This operation is sent to the FE to mark the
            success from an NE perspective of a 2pc transaction.  A
            TRCOMP TLV is an empty TLV, i.e., it has no "V"alue.  In
            other words, there is a length of 4 (which is for the
            header only).
 PATH-DATA-TLV:
 This is generically a PATH-DATA-TLV format that has been defined in
 Section 7 in the PATH-DATA-TLV BNF definition.  The restriction on
 the use of PATH-DATA-TLV for SET/SET-PROP operation is that it MUST
 contain either FULLDATA-TLV or SPARSEDATA-TLV(s), but MUST NOT
 contain any RESULT-TLV.  The restriction on the use of PATH-DATA-TLV
 for DEL operation is it MAY contain FULLDATA-TLV or
 SPARSEDATA-TLV(s), but MUST NOT contain any RESULT-TLV.  The
 RESULT-TLV is defined in Section 7.1.7 and FULLDATA-TLVs and
 SPARSEDATA-TLVs are defined in Section 7.1.8.

Doria, et al. Standards Track [Page 70] RFC 5810 ForCES March 2010

     Note:  For Event subscription, the events will be defined by the
            individual LFBs.
 To better illustrate the above PDU format, a tree structure for the
 format is shown below:
 main hdr (type = Config)
  |
  |
  +--- T = LFBselect
  .        |
  .        +-- LFBCLASSID = target LFB class
  .        |
           |
           +-- LFBInstance = target LFB instance
           |
           |
           +-- T = operation { SET }
           |   |
           |   +--  // one or more path targets
           |      // associated with FULLDATA-TLV or SPARSEDATA-TLV(s)
           |
           +-- T = operation { DEL }
           |   |
           |   +--  // one or more path targets
           |
           +-- T = operation { COMMIT } //A COMMIT TLV is an empty TLV
                    .
                    .
            Figure 30: PDU Format for Configuration Message

7.6.2. Config Response Message

 This message is sent by the FE to the CE in response to the Config
 message.  It indicates whether or not the Config was successful on
 the FE and also gives a detailed response regarding the configuration
 result of each component.
 Message transfer direction:
 FE to CE

Doria, et al. Standards Track [Page 71] RFC 5810 ForCES March 2010

 Message header:
 The Message Type in the header is set to MessageType= 'Config
 Response'.  The ACK flag in the header is always ignored, and the
 Config Response message never expects to get any further response
 from the message receiver (CE).
 OPER-TLV for Config Response:
   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |          Type                 |               Length          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                        PATH-DATA-TLV                          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                  Figure 31: OPER-TLV for Config Response
 Type:
        The operation type for Config Response message.  Two types of
        operations for the Config Response message are defined:
     Type = "SET-RESPONSE" - This operation is for the response of the
            SET operation of LFB components.
     Type = "SET-PROP-RESPONSE" - This operation is for the response
            of the SET-PROP operation of LFB component properties.
     Type = "DEL-RESPONSE" - This operation is for the response of the
            DELETE operation of LFB components.
     Type = "COMMIT-RESPONSE" - This operation is sent to the CE to
            confirm a commit success in a 2pc transaction.  A
            COMMIT-RESPONSE TLV MUST contain a RESULT-TLV indicating
            success or failure.
 PATH-DATA-TLV:
 This is generically a PATH-DATA-TLV format that has been defined in
 Section 7 in the PATH-DATA-TLV BNF definition.  The restriction on
 the use of PATH-DATA-TLV for SET-RESPONSE operation is that it MUST
 contain RESULT-TLV(s).  The restriction on the use of PATH-DATA-TLV
 for DEL-RESPONSE operation is it also MUST contain RESULT-TLV(s).
 The RESULT-TLV is defined in Section 7.1.7.

Doria, et al. Standards Track [Page 72] RFC 5810 ForCES March 2010

 To better illustrate the above PDU format, a tree structure for the
 format is shown below:
  main hdr (type = ConfigResponse)
   |
   |
   +--- T = LFBselect
   .        |
   .        +-- LFBCLASSID = target LFB class
   .        |
            |
            +-- LFBInstance = target LFB instance
            |
            |
            +-- T = operation { SET-RESPONSE }
            |   |
            |   +--  // one or more path targets
            |        // associated with FULL or SPARSEDATA-TLV(s)
            |
            +-- T = operation { DEL-RESPONSE }
            |   |
            |   +--  // one or more path targets
            |
            +-- T = operation { COMMIT-RESPONSE }
            |           |
            |           +--  RESULT-TLV
           Figure 32: PDU Format for Config Response Message

7.7. Query Messages

 The ForCES Query messages are used by the CE to query LFBs in the FE
 for information like LFB components, capabilities, statistics, etc.
 Query messages include the Query message and the Query Response
 message.

7.7.1. Query Message

 A Query message is composed of a common header and a message body
 that consists of one or more TLV data formats.  Detailed description
 of the message is as follows:
 Message transfer direction:
 from CE to FE

Doria, et al. Standards Track [Page 73] RFC 5810 ForCES March 2010

 Message header:
 The Message Type in the header is set to MessageType= 'Query'.  The
 ACK flag in the header is always ignored, and a full response for a
 Query message is always expected.  The Correlator field in the header
 is set, so that the CE can locate the response back from FE
 correctly.
 OPER-TLV for Query:
   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |    Type = GET/GET-PROP        |               Length          |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                    PATH-DATA-TLV for GET/GET-PROP             |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         Figure 33: TLV for Query
 Type:
 The operation type for query.  Two operation types are defined:
     Type = "GET" - This operation is to request to get LFB
            components.
     Type = "GET-PROP" - This operation is to request to get LFB
            component properties.
 PATH-DATA-TLV for GET/GET-PROP:
 This is generically a PATH-DATA-TLV format that has been defined in
 Section 7 in the PATH-DATA-TLV BNF definition.  The restriction on
 the use of PATH-DATA-TLV for GET/GET-PROP operation is it MUST NOT
 contain any SPARSEDATA-TLV or FULLDATA- TLV and RESULT-TLV in the
 data format.

Doria, et al. Standards Track [Page 74] RFC 5810 ForCES March 2010

 To better illustrate the above PDU format, a tree structure for the
 format is shown below:
 main hdr (type = Query)
  |
  |
  +--- T = LFBselect
  .        |
  .        +-- LFBCLASSID = target LFB class
  .        |
           |
           +-- LFBInstance = target LFB instance
           |
           |
           +-- T = operation { GET }
           |   |
           |   +--  // one or more path targets
           |
           +-- T = operation { GET }
           .   |
           .   +--  // one or more path targets
           .
                Figure 34: PDU Format for Query Message

7.7.2. Query Response Message

 When receiving a Query message, the receiver should process the
 message and come up with a query result.  The receiver sends the
 query result back to the message sender by use of the Query Response
 message.  The query result can be the information being queried if
 the query operation is successful, or can also be error codes if the
 query operation fails, indicating the reasons for the failure.
 A Query Response message is also composed of a common header and a
 message body consisting of one or more TLVs describing the query
 result.  Detailed description of the message is as follows:
 Message transfer direction:
 from FE to CE
 Message header:
 The Message Type in the header is set to MessageType=
 'QueryResponse'.  The ACK flag in the header is ignored.  As a
 response itself, the message does not expect a further response.

Doria, et al. Standards Track [Page 75] RFC 5810 ForCES March 2010

 OPER-TLV for Query Response:
   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |Type = GET-RESPONSE/GET-PROP-RESPONSE|    Length               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |        PATH-DATA-TLV for GET-RESPONSE/GET-PROP-RESPONSE       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                     Figure 35: TLV for Query Response
 Type:
 The operation type for query response.  One operation type is
 defined:
     Type = "GET-RESPONSE" - This operation is for the response of the
            GET operation of LFB components.
     Type = "GET-PROP-RESPONSE" - This operation is for the response
            of the GET-PROP operation of LFB components.
 PATH-DATA-TLV for GET-RESPONSE/GET-PROP-RESPONSE:
 This is generically a PATH-DATA-TLV format that has been defined in
 Section 7 in the PATH-DATA-TLV BNF definition.  The PATH-DATA- TLV
 for the GET-RESPONSE operation MAY contain SPARSEDATA-TLV,
 FULLDATA-TLV, and/or RESULT-TLV(s) in the data encoding.  The
 RESULT-TLV is defined in Section 7.1.7 and the SPARSEDATA-TLVs and
 FULLDATA-TLVs are defined in Section 7.1.8.

Doria, et al. Standards Track [Page 76] RFC 5810 ForCES March 2010

 To better illustrate the above PDU format, a tree structure for the
 format is shown below:
 main hdr (type = QueryResponse)
   |
   |
   +--- T = LFBselect
   .        |
   .        +-- LFBCLASSID = target LFB class
   .        |
            |
            +-- LFBInstance = target LFB instance
            |
            |
            +-- T = operation { GET-RESPONSE }
            |   |
            |   +--  // one or more path targets
            |
            +-- T = operation { GET-PROP-RESPONSE }
            .   |
            .   +--  // one or more path targets
            .
           Figure 36: PDU Format for Query Response Message

7.8. Event Notification Message

 Event Notification message is used by the FE to asynchronously notify
 the CE of events that happen in the FE.
 All events that can be generated in an FE are subscribable by the CE.
 The CE can subscribe to an event via a Config message with the SET-
 PROP operation, where the included path specifies the event, as
 defined by the LFB Library and described by the FE Model.
 As usual, an Event Notification message is composed of a common
 header and a message body that consists of one or more TLV data
 formats.  Detailed description of the message is as follows:
 Message transfer direction:
 FE to CE

Doria, et al. Standards Track [Page 77] RFC 5810 ForCES March 2010

 Message header:
 The Message Type in the message header is set to
 MessageType = 'EventNotification'.  The ACK flag in the header MUST
 be ignored by the CE, and the Event Notification message does not
 expect any response from the receiver.
 OPER-TLV for Event Notification:
  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    Type = REPORT              |               Length          |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                    PATH-DATA-TLV for REPORT                   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                  Figure 37: TLV for Event Notification
 Type:
 Only one operation type is defined for the Event Notification
 message:
    Type = "REPORT" - This type of operation is for the FE to report
           something to the CE.
 PATH-DATA-TLV for REPORT:
 This is generically a PATH-DATA-TLV format that has been defined in
 Section 7 in the PATH-DATA-TLV BNF definition.  The PATH-DATA- TLV
 for the REPORT operation MAY contain FULLDATA-TLV or
 SPARSEDATA-TLV(s) but MUST NOT contain any RESULT-TLV in the data
 format.

Doria, et al. Standards Track [Page 78] RFC 5810 ForCES March 2010

 To better illustrate the above PDU format, a tree structure for the
 format is shown below:
 main hdr (type = Event Notification)
   |
   |
   +--- T = LFBselect
              |
              +-- LFBCLASSID = target LFB class
              |
              |
              +-- LFBInstance = target LFB instance
              |
              |
              +-- T = operation { REPORT }
              |   |
              |   +--  // one or more path targets
              |        // associated with FULL/SPARSE DATA TLV(s)
              +-- T = operation { REPORT }
              .   |
              .   +--  // one or more path targets
              .        // associated with FULL/SPARSE DATA TLV(s)
         Figure 38: PDU Format for Event Notification Message

7.9. Packet Redirect Message

 A Packet Redirect message is used to transfer data packets between
 the CE and FE.  Usually, these data packets are control packets, but
 they may be just data path packets that need further (exception or
 high-touch) processing.  It is also feasible that this message
 carries no data packets and rather just meta data.
 The Packet Redirect message data format is formatted as follows:
 Message transfer direction:
 CE to FE or FE to CE
 Message header:
 The Message Type in the header is set to MessageType=
 'PacketRedirect'.

Doria, et al. Standards Track [Page 79] RFC 5810 ForCES March 2010

 Message body:
 This consists of one or more TLVs that contain or describe the packet
 being redirected.  The TLV is specifically a Redirect TLV (with the
 TLV Type="Redirect").  Detailed data format of a Redirect TLV for a
 Packet Redirect message is as follows:
  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |        Type = Redirect        |               Length          |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                        Meta Data TLV                          |
 .                                                               .
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                        Redirect Data TLV                      |
 .                                                               .
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                       Figure 39: Redirect_Data TLV
 Meta Data TLV:
 This is a TLV that specifies meta data associated with followed
 redirected data.  The TLV is as follows:
  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    Type = METADATA-TLV        |               Length          |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                        Meta Data ILV                          |
 .                                                               .
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 ~                           ...                                 ~
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                        Meta Data ILV                          |
 .                                                               .
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         Figure 40: METADATA-TLV

Doria, et al. Standards Track [Page 80] RFC 5810 ForCES March 2010

 Meta Data ILV:
 This is an Identifier-Length-Value format that is used to describe
 one meta data.  The ILV has the format as:
  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                        Meta Data ID                           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                        Length                                 |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                        Meta Data Value                        |
 .                                                               .
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         Figure 41: Meta Data ILV
 where Meta Data ID is an identifier for the meta data, which is
 statically assigned by the LFB definition.
 Redirect Data TLV:
 This is a TLV describing one packet of data to be directed via the
 redirect operation.  The TLV format is as follows:
  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    Type = REDIRECTDATA-TLV    |               Length          |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                        Redirected Data                        |
 .                                                               .
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                       Figure 42: Redirect Data TLV
 Redirected Data:
 This field contains the packet that is to be redirected in network
 byte order.  The packet should be 32 bits aligned as is the data for
 all TLVs.  The meta data infers what kind of packet is carried in
 value field and therefore allows for easy decoding of data
 encapsulated.

Doria, et al. Standards Track [Page 81] RFC 5810 ForCES March 2010

 To better illustrate the above PDU format, a tree structure for the
 format is shown below:
 main hdr (type = PacketRedirect)
         |
         |
         +--- T = Redirect
         .        |
         .        +-- T = METADATA-TLV
                  |          |
                  |          +--  Meta Data ILV
                  |          |
                  |          +--  Meta Data ILV
                  |          .
                  |          .
                  |
                  +-- T = REDIRECTDATA-TLV
                      |
                      +--  // Redirected Data
           Figure 43: PDU Format for Packet Redirect Message

7.10. Heartbeat Message

 The Heartbeat (HB) message is used for one ForCES element (FE or CE)
 to asynchronously notify one or more other ForCES elements in the
 same ForCES NE on its liveness.  Section 4.3.3 describes the traffic-
 sensitive approach used.
 A Heartbeat message is sent by a ForCES element periodically.  The
 parameterization and policy definition for heartbeats for an FE are
 managed as components of the FE Protocol Object LFB, and can be set
 by CE via a Config message.  The Heartbeat message is a little
 different from other protocol messages in that it is only composed of
 a common header, with the message body left empty.  A detailed
 description of the message is as follows:
 Message transfer direction:
 FE to CE or CE to FE
 Message header:
 The Message Type in the message header is set to MessageType =
 'Heartbeat'.  Section 4.3.3 describes the HB mechanisms used.  The
 ACK flag in the header MUST be set to either 'NoACK' or 'AlwaysACK'
 when the HB is sent.

Doria, et al. Standards Track [Page 82] RFC 5810 ForCES March 2010

  • When set to 'NoACK', the HB is not soliciting for a response.
  • When set to 'AlwaysACK', the HB Message sender is always

expecting a response from its receiver. According to the HB

         policies defined in Section 7.3.1, only the CE can send such
         an HB message to query FE liveness.  For simplicity and
         because of the minimal nature of the HB message, the response
         to an HB message is another HB message, i.e., no specific HB
         Response message is defined.  Whenever an FE receives an HB
         message marked with 'AlwaysACK' from the CE, the FE MUST send
         an HB message back immediately.  The HB message sent by the
         FE in response to the 'AlwaysACK' MUST modify the source and
         destination IDs so that the ID of the FE is the source ID and
         the CE ID of the sender is the destination ID, and MUST
         change the ACK information to 'NoACK'.  A CE MUST NOT respond
         to an HB message with 'AlwaysACK' set.
  • When set to anything else other than 'NoACK' or 'AlwaysACK',

the HB message is treated as if it was a 'NoACK'.

 The correlator field in the HB message header SHOULD be set
 accordingly when a response is expected so that a receiver can
 correlate the response correctly.  The correlator field MAY be
 ignored if no response is expected.
 Message body:
 The message body is empty for the Heartbeat message.

8. High Availability Support

 The ForCES protocol provides mechanisms for CE redundancy and
 failover, in order to support High Availability as defined in
 [RFC3654].  FE redundancy and FE to FE interaction is currently out
 of scope of this document.  There can be multiple redundant CEs and
 FEs in a ForCES NE.  However, at any one time only one primary CE can
 control the FEs though there can be multiple secondary CEs.  The FE
 and the CE PL are aware of the primary and secondary CEs.  This
 information (primary, secondary CEs) is configured in the FE and in
 the CE PLs during pre-association by the FEM and the CEM
 respectively.  Only the primary CE sends control messages to the FEs.

8.1. Relation with the FE Protocol

 High Availability parameterization in an FE is driven by configuring
 the FE Protocol Object LFB (refer to Appendix B and Section 7.3.1).
 The FE Heartbeat Interval, CE Heartbeat Dead Interval, and CE

Doria, et al. Standards Track [Page 83] RFC 5810 ForCES March 2010

 Heartbeat policy help in detecting connectivity problems between an
 FE and CE.  The CE failover policy defines the reaction on a detected
 failure.
 Figure 44 extends the state machine illustrated in Figure 4 to allow
 for new states that facilitate connection recovery.
     (CE issues Teardown ||    +-----------------+
        Lost association) &&   | Pre-association |
       CE failover policy = 0  | (Association    |
           +------------>-->-->|   in            +<----+
           |                   | progress)       |     |
           |     CE issues     +--------+--------+     |
           |     Association        |                  | CFTI
           |       Setup            V                  | timer
           |     ___________________+                  | expires
           |     |                                     |
           |     V                                     ^
         +-+-----------+                          +-------+-----+
         |             |                          |  Not        |
         |             |  (CE issues Teardown ||  |  Associated |
         |             |    Lost association) &&  |             |
         | Associated  |  CE failover policy = 1  | (May        |
         |             |                          | Continue    |
         |             |---------->------->------>|  Forwarding)|
         |             |                          |             |
         +-------------+                          +-------------+
              ^                                         V
              |                                         |
              |            CE issues                    |
              |            Association                  |
              |            Setup                        |
              +_________________________________________+
              Figure 44: FE State Machine Considering HA
 Section 4.2 describes transitions between the pre-association,
 associated, and not associated states.
 When communication fails between the FE and CE (which can be caused
 by either the CE or link failure but not FE related), either the TML
 on the FE will trigger the FE PL regarding this failure or it will be
 detected using the HB messages between FEs and CEs.  The
 communication failure, regardless of how it is detected, MUST be
 considered as a loss of association between the CE and corresponding
 FE.

Doria, et al. Standards Track [Page 84] RFC 5810 ForCES March 2010

 If the FE's FEPO CE failover policy is configured to mode 0 (the
 default), it will immediately transition to the pre-association
 phase.  This means that if association is again established, all FE
 state will need to be re-established.
 If the FE's FEPO CE failover policy is configured to mode 1, it
 indicates that the FE is capable of HA restart recovery.  In such a
 case, the FE transitions to the not associated state and the CEFTI
 timer is started.  The FE MAY continue to forward packets during this
 state.  It MAY also recycle through any configured secondary CEs in a
 round-robin fashion.  It first adds its primary CE to the tail of
 backup CEs and sets its primary CE to be the first secondary.  It
 then attempts to associate with the CE designated as the new primary
 CE.  If it fails to re-associate with any CE and the CEFTI expires,
 the FE then transitions to the pre-association state.
 If the FE, while in the not associated state, manages to reconnect to
 a new primary CE before CEFTI expires, it transitions to the
 associated state.  Once re-associated, the FE tries to recover any
 state that may have been lost during the not associated state.  How
 the FE achieves this is out of scope for this document.
 Figure 45 below illustrates the ForCES message sequences that the FE
 uses to recover the connection.
       FE                   CE Primary        CE Secondary
       |                       |                    |
       |  Asso Estb,Caps exchg |                    |
     1 |<--------------------->|                    |
       |                       |                    |
       |       All msgs        |                    |
     2 |<--------------------->|                    |
       |                       |                    |
       |                       |                    |
       |                   FAILURE                  |
       |                                            |
       |         Asso Estb,Caps exchange            |
     3 |<------------------------------------------>|
       |                                            |
       |              Event Report (pri CE down)    |
     4 |------------------------------------------->|
       |                                            |
       |                   All Msgs                 |
     5 |<------------------------------------------>|
            Figure 45: CE Failover for Report Primary Mode

Doria, et al. Standards Track [Page 85] RFC 5810 ForCES March 2010

 A CE-to-CE synchronization protocol would be needed to support fast
 failover as well as to address some of the corner cases; however,
 this will not be defined by the ForCES protocol as it is out of scope
 for this specification.
 An explicit message (a Config message setting primary CE component in
 the FE Protocol Object) from the primary CE can also be used to
 change the primary CE for an FE during normal protocol operation.
 Also note that the FEs in a ForCES NE could also use a multicast CE
 ID, i.e., they could be associated with a group of CEs (this assumes
 the use of a CE-CE synchronization protocol, which is out of scope
 for this specification).  In this case, the loss of association would
 mean that communication with the entire multicast group of CEs has
 been lost.  The mechanisms described above will apply for this case
 as well during the loss of association.  If, however, the secondary
 CE was also using the multicast CE ID that was lost, then the FE will
 need to form a new association using a different CE ID.  If the
 capability exists, the FE MAY first attempt to form a new association
 with the original primary CE using a different non-multicast CE ID.

8.2. Responsibilities for HA

 TML level:
 1.  The TML controls logical connection availability and failover.
 2.  The TML also controls peer HA management.
 At this level, control of all lower layers, for example, transport
 level (such as IP addresses, MAC addresses, etc.) and associated
 links going down are the role of the TML.
 PL level:
 All other functionality, including configuring the HA behavior during
 setup, the CE IDs used to identify primary and secondary CEs,
 protocol messages used to report CE failure (Event Report), Heartbeat
 messages used to detect association failure, messages to change the
 primary CE (Config), and other HA-related operations described
 before, are the PL responsibility.
 To put the two together, if a path to a primary CE is down, the TML
 would take care of failing over to a backup path, if one is
 available.  If the CE is totally unreachable, then the PL would be
 informed and it would take the appropriate actions described earlier.

Doria, et al. Standards Track [Page 86] RFC 5810 ForCES March 2010

9. Security Considerations

 The ForCES framework document [RFC3746], Section 8, goes into
 extensive detail on a variety of security threats, the possible
 effects of those threats on the protocol, and responses to those
 threats.  This document does not repeat that discussion; the reader
 is referred to the ForCES framework document [RFC3746] for those
 details and how the ForCES architecture addresses them.
 ForCES PL uses security services provided by the ForCES TML.  The TML
 provides security services such as endpoint authentication service,
 message authentication service, and confidentiality service.
 Endpoint authentication service is invoked at the time of the pre-
 association connection establishment phase and message authentication
 is performed whenever the FE or CE receives a packet from its peer.
 The following are the general security mechanisms that need to be in
 place for ForCES PL.
 o  Security mechanisms are session controlled -- that is, once the
    security is turned on depending upon the chosen security level (No
    Security, Authentication, Confidentiality), it will be in effect
    for the entire duration of the session.
 o  An operator should configure the same security policies for both
    primary and backup FEs and CEs (if available).  This will ensure
    uniform operations and avoid unnecessary complexity in policy
    configuration.

9.1. No Security

 When "No Security" is chosen for ForCES protocol communication, both
 endpoint authentication and message authentication service needs to
 be performed by ForCES PL.  Both these mechanism are weak and do not
 involve cryptographic operation.  An operator can choose "No
 Security" level when the ForCES protocol endpoints are within a
 single box, for example.
 In order to have interoperable and uniform implementation across
 various security levels, each CE and FE endpoint MUST implement this
 level.
 What is described below (in Section 9.1.1 and Section 9.1.2) are
 error checks and not security procedures.  The reader is referred to
 Section 9.2 for security procedures.

Doria, et al. Standards Track [Page 87] RFC 5810 ForCES March 2010

9.1.1. Endpoint Authentication

 Each CE and FE PL maintains a list of associations as part of its
 configuration.  This is done via the CEM and FEM interfaces.  An FE
 MUST connect to only those CEs that are configured via the FEM;
 similarly, a CE should accept the connection and establish
 associations for the FEs which are configured via the CEM.  The CE
 should validate the FE identifier before accepting the connections
 during the pre-association phase.

9.1.2. Message Authentication

 When a CE or FE initiates a message, the receiving endpoint MUST
 validate the initiator of the message by checking the common header
 CE or FE identifiers.  This will ensure proper protocol functioning.
 This extra processing step is recommended even when the underlying
 TML layer security services exist.

9.2. ForCES PL and TML Security Service

 This section is applicable if an operator wishes to use the TML
 security services.  A ForCES TML MUST support one or more security
 services such as endpoint authentication service, message
 authentication service, and confidentiality service, as part of TML
 security layer functions.  It is the responsibility of the operator
 to select an appropriate security service and configure security
 policies accordingly.  The details of such configuration are outside
 the scope of the ForCES PL and are dependent on the type of transport
 protocol and the nature of the connection.
 All these configurations should be done prior to starting the CE and
 FE.
 When certificates-based authentication is being used at the TML, the
 certificate can use a ForCES-specific naming structure as certificate
 names and, accordingly, the security policies can be configured at
 the CE and FE.
 The reader is asked to refer to specific TML documents for details on
 the security requirements specific to that TML.

9.2.1. Endpoint Authentication Service

 When TML security services are enabled, the ForCES TML performs
 endpoint authentication.  Security association is established between
 CE and FE and is transparent to the ForCES PL.

Doria, et al. Standards Track [Page 88] RFC 5810 ForCES March 2010

9.2.2. Message Authentication Service

 This is a TML-specific operation and is transparent to the ForCES PL.
 For details, refer to Section 5.

9.2.3. Confidentiality Service

 This is a TML-specific operation and is transparent to the ForCES PL.
 For details, refer to Section 5.

10. Acknowledgments

 The authors of this document would like to acknowledge and thank the
 ForCES Working Group and especially the following: Furquan Ansari,
 Alex Audu, Steven Blake, Shuchi Chawla, Alan DeKok, Ellen M.
 Deleganes, Xiaoyi Guo, Yunfei Guo, Evangelos Haleplidis, Zsolt
 Haraszti, Fenggen Jia, John C. Lin, Alistair Munro, Jeff Pickering,
 T. Sridhlar, Guangming Wang, Chaoping Wu, and Lily L. Yang, for their
 contributions.  We would also like to thank David Putzolu and Patrick
 Droz for their comments and suggestions on the protocol and for their
 infinite patience.  We would also like to thank Sue Hares and Alia
 Atlas for extensive reviews of the document.
 Alia Atlas did a wonderful job of shaping the document to make it
 more readable by providing the IESG feedback.
 Ross Callon was instrumental in getting us over major humps to
 getting this document published.
 The editors have used the xml2rfc [RFC2629] tools in creating this
 document and are very grateful for the existence and quality of these
 tools.  The editor is also grateful to Elwyn Davies for his help in
 correcting the XML source of this document.

11. References

11.1. Normative References

 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2914]  Floyd, S., "Congestion Control Principles", BCP 41,
            RFC 2914, September 2000.
 [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
            IANA Considerations Section in RFCs", BCP 26, RFC 5226,
            May 2008.

Doria, et al. Standards Track [Page 89] RFC 5810 ForCES March 2010

 [RFC5390]  Rosenberg, J., "Requirements for Management of Overload in
            the Session Initiation Protocol", RFC 5390, December 2008.
 [RFC5811]  Hadi Salim, J. and K. Ogawa, "SCTP-Based Transport Mapping
            Layer (TML) for the Forwarding and Control Element
            Separation (ForCES) Protocol", RFC 5811, March 2010.
 [RFC5812]  Halpern, J. and J. Hadi Salim, "Forwarding and Control
            Element Separation (ForCES) Forwarding Element Model",
            RFC 5812, March 2010.

11.2. Informative References

 [2PCREF]   Gray, J., "Notes on database operating systems", in
            "Operating Systems: An Advanced Course" Lecture Notes in
            Computer Science, Vol. 60, pp. 394-481, Springer-Verlag,
            1978.
 [ACID]     Haerder, T. and A. Reuter, "Principles of Transaction-
            Orientated Database Recovery", 1983.
 [RFC2629]  Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
            June 1999.
 [RFC3654]  Khosravi, H. and T. Anderson, "Requirements for Separation
            of IP Control and Forwarding", RFC 3654, November 2003.
 [RFC3746]  Yang, L., Dantu, R., Anderson, T., and R. Gopal,
            "Forwarding and Control Element Separation (ForCES)
            Framework", RFC 3746, April 2004.

Doria, et al. Standards Track [Page 90] RFC 5810 ForCES March 2010

Appendix A. IANA Considerations

 Following the policies outlined in "Guidelines for Writing an IANA
 Considerations Section in RFCs" (RFC 5226 [RFC5226]), the following
 namespaces are defined in ForCES.
 o  Message Type Namespace, Section 7
 o  Operation Type Namespace, Section 7.1.6
 o  Header Flags, Section 6.1
 o  TLV Type, Section 7
 o  TLV Result Values, Section 7.1.7
 o  LFB Class ID, Section 7.1.5 (resolved by model document,
    [RFC5812].
 o  Result: Association Setup Response, Section 7.5.2
 o  Reason: Association Teardown Message, Section 7.5.3

A.1. Message Type Namespace

 The Message Type is an 8-bit value.  The following is the guideline
 for defining the Message Type namespace:
 Message Types 0x00 - 0x1F
    Message Types in this range are part of the base ForCES protocol.
    Message Types in this range are allocated through an IETF
    consensus action [RFC5226].
    Values assigned by this specification:
     0x00               Reserved
     0x01               AssociationSetup
     0x02               AssociationTeardown
     0x03               Config
     0x04               Query
     0x05               EventNotification
     0x06               PacketRedirect
     0x07 - 0x0E        Reserved
     0x0F               Hearbeat
     0x11               AssociationSetupResponse
     0x12               Reserved
     0x13               ConfigResponse
     0x14               QueryResponse

Doria, et al. Standards Track [Page 91] RFC 5810 ForCES March 2010

 Message Types 0x20 - 0x7F
    Message Types in this range are Specification Required [RFC5226].
    Message Types using this range MUST be documented in an RFC or
    other permanent and readily available reference.
 Message Types 0x80 - 0xFF
    Message Types in this range are reserved for vendor private
    extensions and are the responsibility of individual vendors.  IANA
    management of this range of the Message Type namespace is
    unnecessary.

A.2. Operation Selection

 The Operation Selection (OPER-TLV) namespace is 16 bits long.  The
 following is the guideline for managing the OPER-TLV namespace.
 OPER-TLV Type 0x0000-0x0FF
    OPER-TLV Types in this range are allocated through an IETF
    consensus process [RFC5226].
    Values assigned by this specification:
               0x0000           Reserved
               0x0001           SET
               0x0002           SET-PROP
               0x0003           SET-RESPONSE
               0x0004           SET-PROP-RESPONSE
               0x0005           DEL
               0x0006           DEL-RESPONSE
               0x0007           GET
               0x0008           GET-PROP
               0x0009           GET-RESPONSE
               0x000A           GET-PROP-RESPONSE
               0x000B           REPORT
               0x000C           COMMIT
               0x000D           COMMIT-RESPONSE
               0x000E           TRCOMP
 OPER-TLV Type 0x0100-0x7FFF
    OPER-TLV Types using this range MUST be documented in an RFC or
    other permanent and readily available reference [RFC5226].
 OPER-TLV Type 0x8000-0xFFFF
    OPER-TLV Types in this range are reserved for vendor private
    extensions and are the responsibility of individual vendors.  IANA
    management of this range of the OPER-TLV Type namespace is
    unnecessary.

Doria, et al. Standards Track [Page 92] RFC 5810 ForCES March 2010

A.3. Header Flags

    The Header flag field is 32 bits long.  Header flags are part of
    the ForCES base protocol.  Header flags are allocated through an
    IETF consensus action [RFC5226].

A.4. TLV Type Namespace

 The TLV Type namespace is 16 bits long.  The following is the
 guideline for managing the TLV Type namespace.
 TLV Type 0x0000-0x01FF
    TLV Types in this range are allocated through an IETF consensus
    process [RFC5226].
    Values assigned by this specification:
               0x0000           Reserved
               0x0001           REDIRECT-TLV
               0x0010           ASResult-TLV
               0x0011           ASTreason-TLV
               0x1000           LFBselect-TLV
               0x0110           PATH-DATA-TLV
               0x0111           KEYINFO-TLV
               0x0112           FULLDATA-TLV
               0x0113           SPARSEDATA-TLV
               0x0114           RESULT-TLV
               0x0115           METADATA-TLV
               0x0116           REDIRECTDATA-TLV
 TLV Type 0x0200-0x7FFF
    TLV Types using this range MUST be documented in an RFC or other
    permanent and readily available reference [RFC5226].
 TLV Type 0x8000-0xFFFF
    TLV Types in this range are reserved for vendor private extensions
    and are the responsibility of individual vendors.  IANA management
    of this range of the TLV Type namespace is unnecessary.

Doria, et al. Standards Track [Page 93] RFC 5810 ForCES March 2010

A.5. RESULT-TLV Result Values

 The RESULT-TLV RTesult Value is an 8-bit value.
              0x00        E_SUCCESS
              0x01        E_INVALID_HEADER
              0x02        E_LENGTH_MISMATCH
              0x03        E_VERSION_MISMATCH
              0x04        E_INVALID_DESTINATION_PID
              0x05        E_LFB_UNKNOWN
              0x06        E_LFB_NOT_FOUND
              0x07        E_LFB_INSTANCE_ID_NOT_FOUND
              0x08        E_INVALID_PATH
              0x09        E_COMPONENT_DOES_NOT_EXIST
              0x0A        E_EXISTS
              0x0B        E_NOT_FOUND
              0x0C        E_READ_ONLY
              0x0D        E_INVALID_ARRAY_CREATION
              0x0E        E_VALUE_OUT_OF_RANGE
              0x0F        E_CONTENTS_TOO_LONG
              0x10        E_INVALID_PARAMETERS
              0x11        E_INVALID_MESSAGE_TYPE
              0x12        E_E_INVALID_FLAGS
              0x13        E_INVALID_TLV
              0x14        E_EVENT_ERROR
              0x15        E_NOT_SUPPORTED
              0x16        E_MEMORY_ERROR
              0x17        E_INTERNAL_ERROR
              0x18-0xFE   Reserved
              0xFF        E_UNSPECIFIED_ERROR
 All values not assigned in this specification are designated as
 Assignment by Expert Review.

A.6. Association Setup Response

 The Association Setup Response namespace is 32 bits long.  The
 following is the guideline for managing the Association Setup
 Response namespace.
 Association Setup Response 0x0000-0x00FF
    Association Setup Responses in this range are allocated through an
    IETF consensus process [RFC5226].

Doria, et al. Standards Track [Page 94] RFC 5810 ForCES March 2010

    Values assigned by this specification:
        0x0000   Success
        0x0001   FE ID Invalid
        0x0002   Permission Denied
 Association Setup Response 0x0100-0x0FFF
    Association Setup Responses in this range are Specification
    Required [RFC5226].  Values using this range MUST be documented in
    an RFC or other permanent and readily available reference
    [RFC5226].
 Association Setup Response 0x1000-0xFFFF
    Association Setup Responses in this range are reserved for vendor
    private extensions and are the responsibility of individual
    vendors.  IANA management of this range of the Association Setup
    Response namespace is unnecessary.

A.7. Association Teardown Message

 The Association Teardown Message namespace is 32 bits long.  The
 following is the guideline for managing the Association Teardown
 Message namespace.
 Association Teardown Message 0x00000000-0x0000FFFF
    Association Teardown Messages in this range are allocated through
    an IETF consensus process [RFC5226].
    Values assigned by this specification:
         0x00000000        Normal - teardown by administrator
         0x00000001        Error  - loss of heartbeats
         0x00000002        Error  - loss of bandwidth
         0x00000003        Error  - out of Memory
         0x00000004        Error  - application crash
         0x000000FF        Error  - unspecified
 Association Teardown Message 0x00010000-0x7FFFFFFF
    Association Teardown Messages in this range are Specification
    Required [RFC5226].  Association Teardown Messages using this
    range MUST be documented in an RFC or other permanent and readily
    available references.  [RFC5226].
 Association Teardown Message 0x80000000-0xFFFFFFFFF
    Association Teardown Messages in this range are reserved for
    vendor private extensions and are the responsibility of individual

Doria, et al. Standards Track [Page 95] RFC 5810 ForCES March 2010

    vendors.  IANA management of this range of the Association
    Teardown Message namespace is unnecessary.

Appendix B. ForCES Protocol LFB Schema

 The schema described below conforms to the LFB schema described in
 the ForCES model [RFC5812].
 Section 7.3.1 describes the details of the different components
 defined in this definition.
 <LFBLibrary xmlns="urn:ietf:params:xml:ns:forces:lfbmodel:1.0"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     provides="FEPO">
 <!-- XXX  -->
   <dataTypeDefs>
      <dataTypeDef>
         <name>CEHBPolicyValues</name>
                <synopsis>
                    The possible values of CE heartbeat policy
                </synopsis>
            <atomic>
            <baseType>uchar</baseType>
            <specialValues>
               <specialValue value="0">
                 <name>CEHBPolicy0</name>
                 <synopsis>
                      The CE heartbeat policy 0
                 </synopsis>
                 </specialValue>
               <specialValue value="1">
                  <name>CEHBPolicy1</name>
                  <synopsis>
                       The CE heartbeat policy 1
                  </synopsis>
               </specialValue>
             </specialValues>
             </atomic>
       </dataTypeDef>
       <dataTypeDef>
          <name>FEHBPolicyValues</name>
               <synopsis>
                   The possible values of FE heartbeat policy
              </synopsis>
            <atomic>
            <baseType>uchar</baseType>
            <specialValues>

Doria, et al. Standards Track [Page 96] RFC 5810 ForCES March 2010

              <specialValue value="0">
                <name>FEHBPolicy0</name>
                <synopsis>
                     The FE heartbeat policy 0
                </synopsis>
              </specialValue>
              <specialValue value="1">
                 <name>FEHBPolicy1</name>
                 <synopsis>
                      The FE heartbeat policy 1
                 </synopsis>
                </specialValue>
             </specialValues>
             </atomic>
       </dataTypeDef>
       <dataTypeDef>
       <name>FERestartPolicyValues</name>
             <synopsis>
                 The possible values of FE restart policy
             </synopsis>
            <atomic>
            <baseType>uchar</baseType>
            <specialValues>
               <specialValue value="0">
                 <name>FERestartPolicy0</name>
                 <synopsis>
                      The FE restart policy 0
                 </synopsis>
                 </specialValue>
             </specialValues>
             </atomic>
       </dataTypeDef>
       <dataTypeDef>
       <name>CEFailoverPolicyValues</name>
             <synopsis>
                 The possible values of CE failover policy
             </synopsis>
            <atomic>
            <baseType>uchar</baseType>
            <specialValues>
              <specialValue value="0">
                 <name>CEFailoverPolicy0</name>
                 <synopsis>
                      The CE failover policy 0
                 </synopsis>
               </specialValue>

Doria, et al. Standards Track [Page 97] RFC 5810 ForCES March 2010

             <specialValue value="1">
                <name>CEFailoverPolicy1</name>
                <synopsis>
                     The CE failover policy 1
                </synopsis>
              </specialValue>
             </specialValues>
             </atomic>
       </dataTypeDef>
      <dataTypeDef>
         <name>FEHACapab</name>
                <synopsis>
                    The supported HA features
                </synopsis>
            <atomic>
            <baseType>uchar</baseType>
            <specialValues>
               <specialValue value="0">
                 <name>GracefullRestart</name>
                 <synopsis>
                      The FE supports Graceful Restart
                 </synopsis>
                 </specialValue>
               <specialValue value="1">
                  <name>HA</name>
                  <synopsis>
                       The FE supports HA
                  </synopsis>
               </specialValue>
             </specialValues>
             </atomic>
       </dataTypeDef>
   </dataTypeDefs>
   <LFBClassDefs>
     <LFBClassDef LFBClassID="2">
       <name>FEPO</name>
       <synopsis>
          The FE Protocol Object
       </synopsis>
       <version>1.0</version>
   <components>
         <component componentID="1" access="read-only">
             <name>CurrentRunningVersion</name>
             <synopsis>Currently running ForCES version</synopsis>
             <typeRef>uchar</typeRef>

Doria, et al. Standards Track [Page 98] RFC 5810 ForCES March 2010

           </component>
         <component componentID="2" access="read-only">
           <name>FEID</name>
           <synopsis>Unicast FEID</synopsis>
           <typeRef>uint32</typeRef>
         </component>
         <component componentID="3" access="read-write">
            <name>MulticastFEIDs</name>
            <synopsis>
               the table of all multicast IDs
            </synopsis>
            <array type="variable-size">
             <typeRef>uint32</typeRef>
            </array>
         </component>
         <component componentID="4" access="read-write">
           <name>CEHBPolicy</name>
           <synopsis>
            The CE Heartbeat Policy
           </synopsis>
           <typeRef>CEHBPolicyValues</typeRef>
         </component>
         <component componentID="5" access="read-write">
           <name>CEHDI</name>
           <synopsis>
             The CE Heartbeat Dead Interval in millisecs
           </synopsis>
           <typeRef>uint32</typeRef>
         </component>
         <component componentID="6" access="read-write">
           <name>FEHBPolicy</name>
           <synopsis>
             The FE Heartbeat Policy
           </synopsis>
           <typeRef>FEHBPolicyValues</typeRef>
         </component>
         <component componentID="7" access="read-write">
           <name>FEHI</name>
           <synopsis>
             The FE Heartbeat Interval in millisecs
           </synopsis>
           <typeRef>uint32</typeRef>
         </component>
         <component componentID="8" access="read-write">
           <name>CEID</name>
           <synopsis>
              The Primary CE this FE is associated with
           </synopsis>

Doria, et al. Standards Track [Page 99] RFC 5810 ForCES March 2010

           <typeRef>uint32</typeRef>
         </component>
         <component componentID="9" access="read-write">
            <name>BackupCEs</name>
            <synopsis>
               The table of all backup CEs other than the primary
            </synopsis>
            <array type="variable-size">
             <typeRef>uint32</typeRef>
            </array>
         </component>
         <component componentID="10" access="read-write">
           <name>CEFailoverPolicy</name>
           <synopsis>
             The CE Failover Policy
           </synopsis>
           <typeRef>CEFailoverPolicyValues</typeRef>
         </component>
         <component componentID="11" access="read-write">
           <name>CEFTI</name>
           <synopsis>
             The CE Failover Timeout Interval in millisecs
           </synopsis>
           <typeRef>uint32</typeRef>
         </component>
         <component componentID="12" access="read-write">
           <name>FERestartPolicy</name>
           <synopsis>
              The FE Restart Policy
           </synopsis>
           <typeRef>FERestartPolicyValues</typeRef>
         </component>
         <component componentID="13" access="read-write">
           <name>LastCEID</name>
           <synopsis>
              The Primary CE this FE was last associated with
           </synopsis>
           <typeRef>uint32</typeRef>
         </component>
       </components>
      <capabilities>
           <capability componentID="30">
              <name>SupportableVersions</name>
              <synopsis>
                 the table of ForCES versions that FE supports

Doria, et al. Standards Track [Page 100] RFC 5810 ForCES March 2010

              </synopsis>
              <array type="variable-size">
               <typeRef>uchar</typeRef>
              </array>
            </capability>
         <capability componentID="31">
            <name>HACapabilities</name>
            <synopsis>
               the table of HA capabilities the FE supports
            </synopsis>
            <array type="variable-size">
             <typeRef>FEHACapab</typeRef>
            </array>
         </capability>
       </capabilities>
       <events baseID="61">
         <event eventID="1">
           <name>PrimaryCEDown</name>
           <synopsis>
               The pimary CE has changed
           </synopsis>
           <eventTarget>
               <eventField>LastCEID</eventField>
           </eventTarget>
           <eventChanged/>
           <eventReports>
              <eventReport>
                <eventField>LastCEID</eventField>
              </eventReport>
           </eventReports>
         </event>
       </events>
     </LFBClassDef>
   </LFBClassDefs>
 </LFBLibrary>

Doria, et al. Standards Track [Page 101] RFC 5810 ForCES March 2010

B.1. Capabilities

 Supportable Versions enumerates all ForCES versions that an FE
 supports.
 FEHACapab enumerates the HA capabilities of the FE.  If the FE is not
 capable of graceful restarts or HA, then it will not be able to
 participate in HA as described in Section 8.1.

B.2. Components

 All components are explained in Section 7.3.1.

Doria, et al. Standards Track [Page 102] RFC 5810 ForCES March 2010

Appendix C. Data Encoding Examples

 In this section a few examples of data encoding are discussed.  These
 example, however, do not show any padding.
 ==========
 Example 1:
 ==========
 Structure with three fixed-lengthof, mandatory fields.
         struct S {
         uint16 a
         uint16 b
         uint16 c
         }
 (a) Describing all fields using SPARSEDATA-TLV
         PATH-DATA-TLV
           Path to an instance of S ...
           SPARSEDATA-TLV
             ComponentIDof(a), lengthof(a), valueof(a)
             ComponentIDof(b), lengthof(b), valueof(b)
             ComponentIDof(c), lengthof(c), valueof(c)
 (b) Describing a subset of fields
         PATH-DATA-TLV
           Path to an instance of S ...
           SPARSEDATA-TLV
             ComponentIDof(a), lengthof(a), valueof(a)
             ComponentIDof(c), lengthof(c), valueof(c)
 Note: Even though there are non-optional components in structure S,
 since one can uniquely identify components, one can selectively send
 components of structure S (e.g., in the case of an update from CE to
 FE).
 (c) Describing all fields using a FULLDATA-TLV
         PATH-DATA-TLV
           Path to an instance of S ...
           FULLDATA-TLV
             valueof(a)
             valueof(b)
             valueof(c)

Doria, et al. Standards Track [Page 103] RFC 5810 ForCES March 2010

 ==========
 Example 2:
 ==========
 Structure with three fixed-lengthof fields, one mandatory, two
 optional.
         struct T {
         uint16 a
         uint16 b (optional)
         uint16 c (optional)
         }
 This example is identical to example 1, as illustrated below.
 (a) Describing all fields using SPARSEDATA-TLV
         PATH-DATA-TLV
           Path to an instance of S ...
           SPARSEDATA-TLV
             ComponentIDof(a), lengthof(a), valueof(a)
             ComponentIDof(b), lengthof(b), valueof(b)
             ComponentIDof(c), lengthof(c), valueof(c)
 (b) Describing a subset of fields using SPARSEDATA-TLV
         PATH-DATA-TLV
           Path to an instance of S ...
           SPARSEDATA-TLV
             ComponentIDof(a), lengthof(a), valueof(a)
             ComponentIDof(c), lengthof(c), valueof(c)
 (c) Describing all fields using a FULLDATA-TLV
         PATH-DATA-TLV
           Path to an instance of S ...
           FULLDATA-TLV
             valueof(a)
             valueof(b)
             valueof(c)
 Note: FULLDATA-TLV _cannot_ be used unless all fields are being
 described.

Doria, et al. Standards Track [Page 104] RFC 5810 ForCES March 2010

 ==========
 Example 3:
 ==========
 Structure with a mix of fixed-lengthof and variable-lengthof fields,
 some mandatory, some optional.  Note in this case, b is variable
 sized.
         struct U {
         uint16 a
         string b (optional)
         uint16 c (optional)
         }
 (a) Describing all fields using SPARSEDATA-TLV
         Path to an instance of U ...
         SPARSEDATA-TLV
           ComponentIDof(a), lengthof(a), valueof(a)
           ComponentIDof(b), lengthof(b), valueof(b)
           ComponentIDof(c), lengthof(c), valueof(c)
 (b) Describing a subset of fields using SPARSEDATA-TLV
         Path to an instance of U ...
         SPARSEDATA-TLV
           ComponentIDof(a), lengthof(a), valueof(a)
           ComponentIDof(c), lengthof(c), valueof(c)
 (c) Describing all fields using FULLDATA-TLV
         Path to an instance of U ...
           FULLDATA-TLV
             valueof(a)
             FULLDATA-TLV
               valueof(b)
             valueof(c)
 Note: The variable-length field requires the addition of a FULLDATA-
 TLV within the outer FULLDATA-TLV as in the case of component b
 above.

Doria, et al. Standards Track [Page 105] RFC 5810 ForCES March 2010

 ==========
 Example 4:
 ==========
 Structure containing an array of another structure type.
         struct V {
         uint32 x
         uint32 y
         struct U z[]
         }
 (a) Encoding using SPARSEDATA-TLV, with two instances of z[], also
 described with SPARSEDATA-TLV, assuming only the 10th and 15th
 subscripts of z[] are encoded.
      path to instance of V ...
      SPARSEDATA-TLV
       ComponentIDof(x), lengthof(x), valueof(x)
       ComponentIDof(y), lengthof(y), valueof(y)
       ComponentIDof(z), lengthof(all below)
         ComponentID = 10 (i.e index 10 from z[]), lengthof(all below)
             ComponentIDof(a), lengthof(a), valueof(a)
             ComponentIDof(b), lengthof(b), valueof(b)
         ComponentID = 15 (index 15 from z[]), lengthof(all below)
             ComponentIDof(a), lengthof(a), valueof(a)
             ComponentIDof(c), lengthof(c), valueof(c)
 Note the holes in the components of z (10 followed by 15).  Also note
 the gap in index 15 with only components a and c appearing but not b.

Doria, et al. Standards Track [Page 106] RFC 5810 ForCES March 2010

Appendix D. Use Cases

 Assume LFB with the following components for the following use cases.
 foo1, type u32, ID = 1
 foo2, type u32, ID = 2
 table1: type array, ID = 3
         components are:
         t1, type u32, ID = 1
         t2, type u32, ID = 2  // index into table2
         KEY: nhkey, ID = 1, V = t2
 table2: type array, ID = 4
         components are:
         j1, type u32, ID = 1
         j2, type u32, ID = 2
         KEY: akey, ID = 1, V = { j1,j2 }
 table3: type array, ID = 5
         components are:
         someid, type u32, ID = 1
         name, type string variable sized, ID = 2
 table4: type array, ID = 6
         components are:
         j1, type u32, ID = 1
         j2, type u32, ID = 2
         j3, type u32, ID = 3
         j4, type u32, ID = 4
         KEY: mykey, ID = 1, V = { j1}
 table5: type array, ID = 7
         components are:
         p1, type u32, ID = 1
         p2, type array, ID = 2, array components of type-X
 Type-X:
         x1, ID 1, type u32
         x2, ID2 , type u32
                 KEY: tkey, ID = 1, V = { x1}
 All examples will use valueof(x) to indicate the value of the
 referenced component x.  In the case where F_SEL** are missing (bits
 equal to 00) then the flags will not show any selection.

Doria, et al. Standards Track [Page 107] RFC 5810 ForCES March 2010

 All the examples only show use of FULLDATA-TLV for data encoding;
 although SPARSEDATA-TLV would make more sense in certain occasions,
 the emphasis is on showing the message layout.  Refer to Appendix C
 for examples that show usage of both FULLDATA-TLV and SPARSEDATA-TLV.
 1.   To get foo1
 OPER = GET-TLV
         PATH-DATA-TLV: IDCount = 1, IDs = 1
 Result:
 OPER = GET-RESPONSE-TLV
         PATH-DATA-TLV:
                 flags=0, IDCount = 1, IDs = 1
                 FULLDATA-TLV L = 4+4, V =  valueof(foo1)
 2.   To set foo2 to 10
 OPER = SET-TLV
         PATH-DATA-TLV:
                 flags = 0,  IDCount = 1, IDs = 2
                 FULLDATA-TLV: L = 4+4, V=10
 Result:
 OPER = SET-RESPONSE-TLV
         PATH-DATA-TLV:
                 flags = 0,  IDCount = 1, IDs = 2
                 RESULT-TLV
 3.   To dump table2
    OPER = GET-TLV
         PATH-DATA-TLV:
                 IDCount = 1, IDs = 4
    Result:
    OPER = GET-RESPONSE-TLV
         PATH-DATA-TLV:
                 flags = 0, IDCount = 1, IDs = 4
                 FULLDATA-TLV: L = XXX, V=
                      a series of: index, valueof(j1), valueof(j2)
                      representing the entire table
      Note:   One should be able to take a GET-RESPONSE-TLV and
         convert it to a SET-TLV.  If the result in the above example
         is sent back in a SET-TLV (instead of a GET-RESPONSE_TLV),
         then the entire contents of the table will be replaced at
         that point.

Doria, et al. Standards Track [Page 108] RFC 5810 ForCES March 2010

 4.   Multiple operations example.  To create entry 0-5 of table2
      (Error conditions are ignored)
 OPER = SET-TLV
         PATH-DATA-TLV:
                 flags = 0 , IDCount = 1, IDs = 4
                 PATH-DATA-TLV
                   flags = 0, IDCount = 1, IDs = 0
                   FULLDATA-TLV valueof(j1), valueof(j2) of entry 0
                 PATH-DATA-TLV
                   flags = 0, IDCount = 1, IDs = 1
                   FULLDATA-TLV valueof(j1), valueof(j2) of entry 1
                 PATH-DATA-TLV
                   flags = 0, IDCount = 1, IDs = 2
                   FULLDATA-TLV valueof(j1), valueof(j2) of entry 2
                 PATH-DATA-TLV
                   flags = 0, IDCount = 1, IDs = 3
                   FULLDATA-TLV valueof(j1), valueof(j2) of entry 3
                 PATH-DATA-TLV
                   flags = 0, IDCount = 1, IDs = 4
                   FULLDATA-TLV valueof(j1), valueof(j2) of entry 4
                 PATH-DATA-TLV
                   flags = 0, IDCount = 1, IDs = 5
                   FULLDATA-TLV valueof(j1), valueof(j2) of entry 5
 Result:
 OPER = SET-RESPONSE-TLV
         PATH-DATA-TLV:
                 flags = 0 , IDCount = 1, IDs = 4
                 PATH-DATA-TLV
                     flags = 0, IDCount = 1, IDs = 0
                     RESULT-TLV
                 PATH-DATA-TLV
                     flags = 0, IDCount = 1, IDs = 1
                     RESULT-TLV
                 PATH-DATA-TLV
                     flags = 0, IDCount = 1, IDs = 2
                     RESULT-TLV
                 PATH-DATA-TLV
                     flags = 0, IDCount = 1, IDs = 3
                     RESULT-TLV
                 PATH-DATA-TLV
                     flags = 0, IDCount = 1, IDs = 4
                     RESULT-TLV
                 PATH-DATA-TLV
                     flags = 0, IDCount = 1, IDs = 5
                     RESULT-TLV

Doria, et al. Standards Track [Page 109] RFC 5810 ForCES March 2010

 5.   Block operations (with holes) example.  Replace entry 0,2 of
      table2.
 OPER = SET-TLV
         PATH-DATA-TLV:
              flags =  0 , IDCount = 1, IDs = 4
              PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 0
                 FULLDATA-TLV containing valueof(j1), valueof(j2) of 0
              PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 2
                 FULLDATA-TLV containing valueof(j1), valueof(j2) of 2
 Result:
 OPER = SET-TLV
         PATH-DATA-TLV:
              flags =  0 , IDCount = 1, IDs = 4
              PATH-DATA-TLV
                  flags = 0, IDCount = 1, IDs = 0
                  RESULT-TLV
              PATH-DATA-TLV
                  flags = 0, IDCount = 1, IDs = 2
                  RESULT-TLV
 6.   Getting rows example.  Get first entry of table2.
 OPER = GET-TLV
         PATH-DATA-TLV:
                 IDCount = 2, IDs = 4.0
 Result:
 OPER = GET-RESPONSE-TLV
         PATH-DATA-TLV:
                 IDCount = 2, IDs = 4.0
                  FULLDATA-TLV containing valueof(j1), valueof(j2)

Doria, et al. Standards Track [Page 110] RFC 5810 ForCES March 2010

 7.   Get entry 0-5 of table2.
 OPER = GET-TLV
         PATH-DATA-TLV:
                 flags = 0, IDCount = 1, IDs = 4
                 PATH-DATA-TLV
                     flags = 0, IDCount = 1, IDs = 0
                 PATH-DATA-TLV
                     flags = 0, IDCount = 1, IDs = 1
                 PATH-DATA-TLV
                     flags = 0, IDCount = 1, IDs = 2
                 PATH-DATA-TLV
                     flags = 0, IDCount = 1, IDs = 3
                 PATH-DATA-TLV
                     flags = 0, IDCount = 1, IDs = 4
                 PATH-DATA-TLV
                     flags = 0, IDCount = 1, IDs = 5
 Result:
 OPER = GET-RESPONSE-TLV
         PATH-DATA-TLV:
                 flags = 0, IDCount = 1, IDs = 4
                 PATH-DATA-TLV
                     flags = 0, IDCount = 1, IDs = 0
                     FULLDATA-TLV containing valueof(j1), valueof(j2)
                 PATH-DATA-TLV
                     flags = 0, IDCount = 1, IDs = 1
                     FULLDATA-TLV containing valueof(j1), valueof(j2)
                 PATH-DATA-TLV
                     flags = 0, IDCount = 1, IDs = 2
                     FULLDATA-TLV containing valueof(j1), valueof(j2)
                 PATH-DATA-TLV
                     flags = 0, IDCount = 1, IDs = 3
                     FULLDATA-TLV containing valueof(j1), valueof(j2)
                 PATH-DATA-TLV
                     flags = 0, IDCount = 1, IDs = 4
                     FULLDATA-TLV containing valueof(j1), valueof(j2)
                 PATH-DATA-TLV
                     flags = 0, IDCount = 1, IDs = 5
                     FULLDATA-TLV containing valueof(j1), valueof(j2)

Doria, et al. Standards Track [Page 111] RFC 5810 ForCES March 2010

 8.   Create a row in table2, index 5.
 OPER = SET-TLV
         PATH-DATA-TLV:
              flags = 0, IDCount = 2, IDs = 4.5
              FULLDATA-TLV containing valueof(j1), valueof(j2)
 Result:
 OPER = SET-RESPONSE-TLV
         PATH-DATA-TLV:
              flags = 0, IDCount = 1, IDs = 4.5
              RESULT-TLV
 9.   Dump contents of table1.
 OPER = GET-TLV
         PATH-DATA-TLV:
                 flags = 0, IDCount = 1, IDs = 3
 Result:
 OPER = GET-RESPONSE-TLV
         PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 3
                 FULLDATA-TLV, Length = XXXX
                         (depending on size of table1)
                         index, valueof(t1),valueof(t2)
                         index, valueof(t1),valueof(t2)
                         .
                         .
                         .

Doria, et al. Standards Track [Page 112] RFC 5810 ForCES March 2010

 10.  Using keys.  Get row entry from table4 where j1=100.  Recall, j1
      is a defined key for this table and its KeyID is 1.
 OPER = GET-TLV
         PATH-DATA-TLV:
                 flags = F_SELKEY  IDCount = 1, IDs = 6
                 KEYINFO-TLV = KeyID=1, KEY_DATA=100
 Result:
 If j1=100 was at index 10
 OPER = GET-RESPONSE-TLV
         PATH-DATA-TLV:
                 flags = 0, IDCount = 1, IDs = 6.10
                 FULLDATA-TLV containing
                   valueof(j1), valueof(j2),valueof(j3),valueof(j4)
 11.  Delete row with KEY match (j1=100, j2=200) in table2.  Note that
      the j1,j2 pair is a defined key for the table2.
 OPER = DEL-TLV
         PATH-DATA-TLV:
                 flags = F_SELKEY  IDCount = 1, IDs = 4
                 KEYINFO-TLV:  {KeyID =1 KEY_DATA=100,200}
 Result:
 If (j1=100, j2=200) was at entry 15:
 OPER = DELETE-RESPONSE-TLV
         PATH-DATA-TLV:
                 flags = 0  IDCount = 2, IDs = 4.15
                 RESULT-TLV

Doria, et al. Standards Track [Page 113] RFC 5810 ForCES March 2010

 12.  Dump contents of table3.  It should be noted that this table has
      a column with a component name that is variable sized.  The
      purpose of this use case is to show how such a component is to
      be encoded.
 OPER = GET-TLV
         PATH-DATA-TLV:
              flags = 0 IDCount = 1, IDs = 5
 Result:
 OPER = GET-RESPONSE-TLV
     PATH-DATA-TLV:
        flags = 0  IDCount = 1, IDs = 5
            FULLDATA-TLV, Length = XXXX
             index, someidv, TLV: T=FULLDATA-TLV, L = 4+strlen(namev),
                    V = valueof(v)
             index, someidv, TLV: T=FULLDATA-TLV, L = 4+strlen(namev),
                    V = valueof(v)
             index, someidv, TLV: T=FULLDATA-TLV, L = 4+strlen(namev),
                    V = valueof(v)
             index, someidv, TLV: T=FULLDATA-TLV, L = 4+strlen(namev),
                    V = valueof(v)
                .
                .
                .

Doria, et al. Standards Track [Page 114] RFC 5810 ForCES March 2010

 13.  Multiple atomic operations.
      Note 1:   This emulates adding a new nexthop entry and then
         atomically updating the L3 entries pointing to an old NH to
         point to a new one.  The assumption is that both tables are
         in the same LFB.
      Note:   Observe the two operations on the LFB instance; both are
         SET operations.
 //Operation 1: Add a new entry to table2 index #20.
 OPER = SET-TLV
         Path-TLV:
                 flags = 0, IDCount = 2,  IDs = 4.20
                 FULLDATA-TLV, V= valueof(j1),valueof(j2)
 // Operation 2: Update table1 entry which
 // was pointing with t2 = 10 to now point to 20
 OPER = SET-TLV
         PATH-DATA-TLV:
                 flags = F_SELKEY, IDCount = 1, IDs = 3
                 KEYINFO-TLV = KeyID=1 KEY_DATA=10
                 PATH-DATA-TLV
                         flags = 0  IDCount = 1, IDs = 2
                         FULLDATA-TLV, V= 20
 Result:
 //first operation, SET
 OPER = SET-RESPONSE-TLV
         PATH-DATA-TLV
                 flags = 0 IDCount = 3, IDs = 4.20
                 RESULT-TLV code = success
                         FULLDATA-TLV, V = valueof(j1),valueof(j2)
 // second operation SET - assuming entry 16 was updated
 OPER = SET-RESPONSE-TLV
         PATH-DATA-TLV
                 flags = 0 IDCount = 2, IDs = 3.16
                 PATH-DATA-TLV
                         flags = 0  IDCount = 1, IDs = 2
                         RESULT-TLV code = success
                                 FULLDATA-TLV, Length = XXXX v=20

Doria, et al. Standards Track [Page 115] RFC 5810 ForCES March 2010

 14.  Selective setting.  On table4 -- for indices 1, 3, 5, 7, and 9.
      Replace j1 to 100, j2 to 200, j3 to 300.  Leave j4 as is.
 PER = SET-TLV
     PATH-DATA-TLV
         flags = 0, IDCount = 1, IDs = 6
         PATH-DATA-TLV
             flags = 0, IDCount = 1, IDs = 1
             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 1
                 FULLDATA-TLV, Length = XXXX, V = {100}
             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 2
                 FULLDATA-TLV, Length = XXXX, V = {200}
             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 3
                 FULLDATA-TLV, Length = XXXX, V = {300}
         PATH-DATA-TLV
             flags = 0, IDCount = 1, IDs = 3
             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 1
                 FULLDATA-TLV, Length = XXXX, V = {100}
             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 2
                 FULLDATA-TLV, Length = XXXX, V = {200}
             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 3
                 FULLDATA-TLV, Length = XXXX, V = {300}

Doria, et al. Standards Track [Page 116] RFC 5810 ForCES March 2010

         PATH-DATA-TLV
             flags = 0, IDCount = 1, IDs = 5
             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 1
                 FULLDATA-TLV, Length = XXXX, V = {100}
             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 2
                 FULLDATA-TLV, Length = XXXX, V = {200}
             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 3
                 FULLDATA-TLV, Length = XXXX, V = {300}
         PATH-DATA-TLV
             flags = 0, IDCount = 1, IDs = 7
             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 1
                 FULLDATA-TLV, Length = XXXX, V = {100}
             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 2
                 FULLDATA-TLV, Length = XXXX, V = {200}
             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 3
                 FULLDATA-TLV, Length = XXXX, V = {300}
         PATH-DATA-TLV
             flags = 0, IDCount = 1, IDs = 9
             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 1
                 FULLDATA-TLV, Length = XXXX, V = {100}
             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 2
                 FULLDATA-TLV, Length = XXXX, V = {200}
             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 3
                 FULLDATA-TLV, Length = XXXX, V = {300}
 response:
 OPER = SET-RESPONSE-TLV
     PATH-DATA-TLV
         flags = 0, IDCount = 1, IDs = 6
         PATH-DATA-TLV
             flags = 0, IDCount = 1, IDs = 1
             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 1
                 RESULT-TLV
             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 2
                 RESULT-TLV

Doria, et al. Standards Track [Page 117] RFC 5810 ForCES March 2010

             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 3
                 RESULT-TLV
         PATH-DATA-TLV
             flags = 0, IDCount = 1, IDs = 3
             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 1
                 RESULT-TLV
             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 2
                 RESULT-TLV
             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 3
                 RESULT-TLV
         PATH-DATA-TLV
             flags = 0, IDCount = 1, IDs = 5
             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 1
                 RESULT-TLV
             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 2
                 RESULT-TLV
             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 3
                 RESULT-TLV
         PATH-DATA-TLV
             flags = 0, IDCount = 1, IDs = 7
             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 1
                 RESULT-TLV
             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 2
                 RESULT-TLV
             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 3
                 RESULT-TLV
         PATH-DATA-TLV
             flags = 0, IDCount = 1, IDs = 9
             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 1
                 RESULT-TLV
             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 2
                 RESULT-TLV
             PATH-DATA-TLV
                 flags = 0, IDCount = 1, IDs = 3
                 RESULT-TLV

Doria, et al. Standards Track [Page 118] RFC 5810 ForCES March 2010

 15.  Manipulation of table of table examples.  Get x1 from table10
      row with index 4, inside table5 entry 10.
 operation = GET-TLV
         PATH-DATA-TLV
                 flags = 0  IDCount = 5, IDs=7.10.2.4.1
 Results:
 operation = GET-RESPONSE-TLV
         PATH-DATA-TLV
                 flags = 0  IDCount = 5, IDs=7.10.2.4.1
                 FULLDATA-TLV: L=XXXX, V = valueof(x1)
 16.  From table5's row 10 table10, get X2s based on the value of x1
      equaling 10 (recall x1 is KeyID 1).
 operation = GET-TLV
         PATH-DATA-TLV
                 flag = F_SELKEY, IDCount=3, IDS = 7.10.2
                 KEYINFO-TLV, KeyID = 1, KEYDATA = 10
                 PATH-DATA-TLV
                         IDCount = 1, IDS = 2 //select x2
 Results:
 If x1=10 was at entry 11:
 operation = GET-RESPONSE-TLV
         PATH-DATA-TLV
                 flag = 0, IDCount=5, IDS = 7.10.2.11
                 PATH-DATA-TLV
                         flags = 0  IDCount = 1, IDS = 2
                         FULLDATA-TLV: L=XXXX, V = valueof(x2)
 17.  Further example of manipulating a table of tables
 Consider table6, which is defined as:
 table6: type array, ID = 8
         components are:
         p1, type u32, ID = 1
         p2, type array, ID = 2, array components of type type-A
 type-A:
         a1, type u32, ID 1,
         a2, type array ID2 ,array components of type type-B
 type-B:
         b1, type u32, ID 1
         b2, type u32, ID 2

Doria, et al. Standards Track [Page 119] RFC 5810 ForCES March 2010

 If for example one wanted to set by replacing:
 table6.10.p1 to 111
 table6.10.p2.20.a1 to 222
 table6.10.p2.20.a2.30.b1 to 333
 in one message and one operation.
 There are two ways to do this:
    a) using nesting
    b) using a flat path data
 A. Method using nesting
    in one message with a single operation
 operation = SET-TLV
         PATH-DATA-TLV
                 flags = 0  IDCount = 2, IDs=6.10
                 PATH-DATA-TLV
                         flags = 0, IDCount = 1, IDs=1
                         FULLDATA-TLV: L=XXXX,
                                 V = {111}
                 PATH-DATA-TLV
                         flags = 0  IDCount = 2, IDs=2.20
                         PATH-DATA-TLV
                                 flags = 0, IDCount = 1, IDs=1
                                 FULLDATA-TLV: L=XXXX,
                                         V = {222}
                         PATH-DATA-TLV :
                                 flags = 0, IDCount = 3, IDs=2.30.1
                                 FULLDATA-TLV: L=XXXX,
                                         V = {333}

Doria, et al. Standards Track [Page 120] RFC 5810 ForCES March 2010

 Result:
 operation = SET-RESPONSE-TLV
         PATH-DATA-TLV
                 flags = 0  IDCount = 2, IDs=6.10
                 PATH-DATA-TLV
                         flags = 0, IDCount = 1, IDs=1
                         RESULT-TLV
                 PATH-DATA-TLV
                         flags = 0  IDCount = 2, IDs=2.20
                         PATH-DATA-TLV
                                 flags = 0, IDCount = 1, IDs=1
                                 RESULT-TLV
                         PATH-DATA-TLV :
                                 flags = 0, IDCount = 3, IDs=2.30.1
                                 RESULT-TLV
 B. Method using a flat path data in
    one message with a single operation
 operation = SET-TLV
         PATH-DATA-TLV :
                 flags = 0, IDCount = 3, IDs=6.10.1
                 FULLDATA-TLV: L=XXXX,
                         V = {111}
         PATH-DATA-TLV :
                 flags = 0, IDCount = 5, IDs=6.10.1.20.1
                 FULLDATA-TLV: L=XXXX,
                         V = {222}
         PATH-DATA-TLV :
                 flags = 0, IDCount = 7, IDs=6.10.1.20.1.30.1
                 FULLDATA-TLV: L=XXXX,
                         V = {333}
 Result:
 operation = SET-TLV
         PATH-DATA-TLV :
                 flags = 0, IDCount = 3, IDs=6.10.1
                 RESULT-TLV
         PATH-DATA-TLV :
                 flags = 0, IDCount = 5, IDs=6.10.1.20.1
                 RESULT-TLV
         PATH-DATA-TLV :
                 flags = 0, IDCount = 7, IDs=6.10.1.20.1.30.1
                 RESULT-TLV

Doria, et al. Standards Track [Page 121] RFC 5810 ForCES March 2010

 18.  Get a whole LFB (all its components, etc.).
      For example:   At startup a CE might well want the entire FE
         Object LFB.  So, in a request targeted at class 1, instance
         1, one might find:
 operation = GET-TLV
         PATH-DATA-TLV
                 flags = 0  IDCount = 0
 result:
 operation = GET-RESPONSE-TLV
         PATH-DATA-TLV
                 flags = 0  IDCount = 0
                 FULLDATA-TLV encoding of the FE Object LFB

Doria, et al. Standards Track [Page 122] RFC 5810 ForCES March 2010

Authors' Addresses

 Avri Doria (editor)
 Lulea University of Technology
 Rainbow Way
 Lulea  SE-971 87
 Sweden
 Phone: +46 73 277 1788
 EMail: avri@ltu.se
 Jamal Hadi Salim (editor)
 Znyx
 Ottawa, Ontario
 Canada
 Phone:
 EMail: hadi@mojatatu.com
 Robert Haas (editor)
 IBM
 Saumerstrasse 4
 8803 Ruschlikon
 Switzerland
 Phone:
 EMail: rha@zurich.ibm.com
 Hormuzd M Khosravi (editor)
 Intel
 2111 NE 25th Avenue
 Hillsboro, OR  97124
 USA
 Phone: +1 503 264 0334
 EMail: hormuzd.m.khosravi@intel.com

Doria, et al. Standards Track [Page 123] RFC 5810 ForCES March 2010

 Weiming Wang  (editor)
 Zhejiang Gongshang University
 18, Xuezheng Str., Xiasha University Town
 Hangzhou  310018
 P.R. China
 Phone: +86-571-28877721
 EMail: wmwang@zjgsu.edu.cn
 Ligang Dong
 Zhejiang Gongshang University
 18, Xuezheng Str., Xiasha University Town
 Hangzhou  310018
 P.R. China
 Phone: +86-571-28877751
 EMail: donglg@zjgsu.edu.cn
 Ram Gopal
 Nokia
 5, Wayside Road
 Burlington, MA  310035
 USA
 Phone: +1-781-993-3685
 EMail: ram.gopal@nsn.com
 Joel Halpern
 P.O. Box 6049
 Leesburg, VA  20178
 USA
 Phone: +1-703-371-3043
 EMail: jmh@joelhalpern.com

Doria, et al. Standards Track [Page 124]

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