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rfc:rfc5787

Internet Engineering Task Force (IETF) D. Papadimitriou Request for Comments: 5787 Alcatel-Lucent Category: Experimental March 2010 ISSN: 2070-1721

              OSPFv2 Routing Protocols Extensions for
       Automatically Switched Optical Network (ASON) Routing

Abstract

 The ITU-T has defined an architecture and requirements for operating
 an Automatically Switched Optical Network (ASON).
 The Generalized Multiprotocol Label Switching (GMPLS) protocol suite
 is designed to provide a control plane for a range of network
 technologies including optical networks such as time division
 multiplexing (TDM) networks including SONET/SDH and Optical Transport
 Networks (OTNs), and lambda switching optical networks.
 The requirements for GMPLS routing to satisfy the requirements of
 ASON routing, and an evaluation of existing GMPLS routing protocols
 are provided in other documents.  This document defines extensions to
 the OSPFv2 Link State Routing Protocol to meet the requirements for
 routing in an ASON.
 Note that this work is scoped to the requirements and evaluation
 expressed in RFC 4258 and RFC 4652 and the ITU-T Recommendations
 current when those documents were written.  Future extensions of
 revisions of this work may be necessary if the ITU-T Recommendations
 are revised or if new requirements are introduced into a revision of
 RFC 4258.

Status of This Memo

 This document is not an Internet Standards Track specification; it is
 published for examination, experimental implementation, and
 evaluation.
 This document defines an Experimental Protocol for the Internet
 community.  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).  Not
 all documents approved by the IESG are a candidate for any level of
 Internet Standard; see Section 2 of RFC 5741.

Papdimitriou Experimental [Page 1] RFC 5787 ASON Routing for OSPFv2 Protocols March 2010

 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/rfc5787.

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.

Papdimitriou Experimental [Page 2] RFC 5787 ASON Routing for OSPFv2 Protocols March 2010

Table of Contents

 1. Introduction ....................................................4
    1.1. Conventions Used in This Document ..........................5
 2. Routing Areas, OSPF Areas, and Protocol Instances ...............5
 3. Reachability ....................................................6
    3.1. Node IPv4 Local Prefix Sub-TLV .............................6
    3.2. Node IPv6 Local Prefix Sub-TLV .............................7
 4. Link Attribute ..................................................8
    4.1. Local Adaptation ...........................................8
    4.2. Bandwidth Accounting .......................................9
 5. Routing Information Scope .......................................9
    5.1. Terminology and Identification .............................9
    5.2. Link Advertisement (Local and Remote TE Router ID
         Sub-TLV) ..................................................10
    5.3. Reachability Advertisement (Local TE Router ID sub-TLV) ...11
 6. Routing Information Dissemination ..............................12
    6.1. Import/Export Rules .......................................13
    6.2. Discovery and Selection ...................................13
         6.2.1. Upward Discovery and Selection .....................13
         6.2.2. Downward Discovery and Selection ...................14
         6.2.3. Router Information Experimental Capabilities TLV ...16
    6.3. Loop Prevention ...........................................16
         6.3.1. Associated RA ID ...................................17
         6.3.2. Processing .........................................18
    6.4. Resiliency ................................................19
    6.5. Neighbor Relationship and Routing Adjacency ...............20
    6.6. Reconfiguration ...........................................20
 7. OSPFv2 Scalability .............................................21
 8. Security Considerations ........................................21
 9. Experimental Code Points .......................................21
    9.1. Sub-TLVs of the Link TLV ..................................22
    9.2. Sub-TLVs of the Node Attribute TLV ........................22
    9.3. Sub-TLVs of the Router Address TLV ........................23
    9.4. TLVs of the Router Information LSA ........................23
 10. References ....................................................24
    10.1. Normative References .....................................24
    10.2. Informative References ...................................25
 11. Acknowledgements ..............................................26
 Appendix A. ASON Terminology ......................................27
 Appendix B. ASON Routing Terminology ..............................28

Papdimitriou Experimental [Page 3] RFC 5787 ASON Routing for OSPFv2 Protocols March 2010

1. Introduction

 The Generalized Multiprotocol Label Switching (GMPLS) [RFC3945]
 protocol suite is designed to provide a control plane for a range of
 network technologies including optical networks such as time division
 multiplexing (TDM) networks including SONET/SDH and Optical Transport
 Networks (OTNs), and lambda switching optical networks.
 The ITU-T defines the architecture of the Automatically Switched
 Optical Network (ASON) in [G.8080].
 [RFC4258] details the routing requirements for the GMPLS suite of
 routing protocols to support the capabilities and functionality of
 ASON control planes identified in [G.7715] and in [G.7715.1].
 [RFC4652] evaluates the IETF Link State routing protocols against the
 requirements identified in [RFC4258].  Section 7.1 of [RFC4652]
 summarizes the capabilities to be provided by OSPFv2 [RFC2328] in
 support of ASON routing.  This document details the OSPFv2 specifics
 for ASON routing.
 Multi-layer transport networks are constructed from multiple networks
 of different technologies operating in a client-server relationship.
 The ASON routing model includes the definition of routing levels that
 provide scaling and confidentiality benefits.  In multi-level
 routing, domains called routing areas (RAs) are arranged in a
 hierarchical relationship.  Note that as described in [RFC4652] there
 is no implied relationship between multi-layer transport networks and
 multi-level routing.  The multi-level routing mechanisms described in
 this document work for both single-layer and multi-layer networks.
 Implementations may support a hierarchical routing topology (multi-
 level) for multiple transport network layers and/or a hierarchical
 routing topology for a single transport network layer.
 This document details the processing of the generic (technology-
 independent) link attributes that are defined in [RFC3630],
 [RFC4202], and [RFC4203] and that are extended in this document.  As
 detailed in Section 4.2, technology-specific traffic engineering
 attributes (and their processing) may be defined in other documents
 that complement this document.
 Note that this work is scoped to the requirements and evaluation
 expressed in [RFC4258] and [RFC4652] and the ITU-T Recommendations
 current when those documents were written.  Future extensions of
 revisions of this work may be necessary if the ITU-T Recommendations
 are revised or if new requirements are introduced into a revision of
 [RFC4258].

Papdimitriou Experimental [Page 4] RFC 5787 ASON Routing for OSPFv2 Protocols March 2010

 This document is classified as Experimental.  Significant changes to
 routing protocols are of concern to the stability of the Internet.
 The extensions described in this document are intended for cautious
 use in self-contained environments.  The objective is to determine
 whether these extensions are stable and functional, whether there is
 a demand for implementation and deployment, and whether the
 extensions have any impact on existing routing protocol deployments.

1.1. Conventions Used in This Document

 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].
 The reader is assumed to be familiar with the terminology and
 requirements developed in [RFC4258] and the evaluation outcomes
 detailed in [RFC4652].
 General ASON terminology is provided in Appendix A.  ASON routing
 terminology is described in Appendix B.

2. Routing Areas, OSPF Areas, and Protocol Instances

 An ASON routing area (RA) represents a partition of the data plane,
 and its identifier is used within the control plane as the
 representation of this partition.
 RAs are arranged in hierarchical levels such that any one RA may
 contain multiple other RAs, and is wholly contained by a single RA.
 Thus, an RA may contain smaller RAs inter-connected by links.  The
 limit of the subdivision results in an RA that contains just two sub-
 networks interconnected by a single link.
 An ASON RA can be mapped to an OSPF area, but the hierarchy of ASON
 RA levels does not map to the hierarchy of OSPF routing areas.
 Instead, successive hierarchical levels of RAs MUST be represented by
 separate instances of the protocol.  Thus, inter-level routing
 information exchange (as described in Section 6) involves the export
 and import of routing information between protocol instances.
 An ASON RA may therefore be identified by the combination of its OSPF
 instance identifier and its OSPF area identifier.  With proper and
 careful network-wide configuration, this can be achieved using just
 the OSPF area identifier, and this process is RECOMMENDED in this
 document.  These concepts and the subsequent handling of network
 reconfiguration is discussed in Section 6.

Papdimitriou Experimental [Page 5] RFC 5787 ASON Routing for OSPFv2 Protocols March 2010

3. Reachability

 In order to advertise blocks of reachable address prefixes, a
 summarization mechanism is introduced that complements the techniques
 described in [RFC5786].
 This extension takes the form of a network mask (a 32-bit number
 indicating the range of IP addresses residing on a single IP
 network/subnet).  The set of local addresses is carried in an OSPFv2
 TE LSA Node Attribute TLV (a specific sub-TLV is defined per address
 family, i.e., IPv4 and IPv6, used as network-unique identifiers).
 The proposed solution is to advertise the local address prefixes of a
 router as new sub-TLVs of the (OSPFv2 TE LSA) Node Attribute top-
 level TLV.  This document defines the following sub-TLVs:
  1. Node IPv4 Local Prefix sub-TLV: Length: variable
  2. Node IPv6 Local Prefix sub-TLV: Length: variable

3.1. Node IPv4 Local Prefix Sub-TLV

 The Type field of the Node IPv4 Local Prefix sub-TLV is assigned a
 value in the range 32768-32777 agreed to by all participants in the
 experiment.  The Value field of this sub-TLV contains one or more
 local IPv4 prefixes.  The Length is measured in bytes and, as defined
 in [RFC3630], reports the length in bytes of the Value part of the
 sub-TLV.  It is set to 8 x n, where n is the number of local IPv4
 prefixes included in the sub-TLV.
 The Node IPv4 Local Prefix sub-TLV has the following format:
   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 (8 x n)        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                         Network Mask 1                        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                         IPv4 Address 1                        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                                                               |
  //                             ...                              //
  |                                                               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                         Network Mask n                        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                         IPv4 Address n                        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Papdimitriou Experimental [Page 6] RFC 5787 ASON Routing for OSPFv2 Protocols March 2010

 Network mask i: A 32-bit number indicating the IPv4 address mask for
 the ith advertised destination prefix.
 Each <Network mask, IPv4 Address> pair listed as part of this sub-TLV
 represents a reachable destination prefix hosted by the advertising
 Router ID.
 The local addresses that can be learned from Opaque TE LSAs (that is,
 the router address and TE interface addresses) SHOULD NOT be
 advertised in the node IPv4 Local Prefix sub-TLV.

3.2. Node IPv6 Local Prefix Sub-TLV

 The Type field of the Node IPv6 Local Prefix sub-TLV is assigned a
 value in the range 32768-32777 agreed to by all participants in the
 experiment.  The Value field of this sub-TLV contains one or more
 local IPv6 prefixes.  IPv6 Prefix representation uses [RFC5340],
 Section A.4.1.
 The Node IPv6 Local Prefix sub-TLV has the following format:
  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             |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | PrefixLength  | PrefixOptions |             (0)               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 |                     IPv6 Address Prefix 1                     |
 |                                                               |
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 //                             ...                              //
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | PrefixLength  | PrefixOptions |             (0)               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 |                     IPv6 Address Prefix n                     |
 |                                                               |
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Papdimitriou Experimental [Page 7] RFC 5787 ASON Routing for OSPFv2 Protocols March 2010

 Length reports the length of the Value part of the sub-TLV in bytes.
 It is set to the sum over all of the local prefixes included in the
 sub-TLV of (4 + (number of 32-bit words in the prefix) * 4).
 The encoding of each prefix potentially using fewer than four 32-bit
 words is described below.
   PrefixLength: Length in bits of the prefix.
   PrefixOptions: 8-bit field describing various capabilities
     associated with the prefix (see [RFC5340], Section A.4.2).
   IPv6 Address Prefix i: The ith IPv6 address prefix in the list.
     Each prefix is encoded in an even multiple of 32-bit words using
     the fewest pairs of 32-bit words necessary to include the entire
     prefix.  Thus, each prefix is encoded in either 64 or 128 bits
     with trailing zero bit padding as necessary.
 The local addresses that can be learned from TE LSAs, i.e., router
 address and TE interface addresses, SHOULD NOT be advertised in the
 node IPv6 Local Prefix sub-TLV.

4. Link Attribute

 [RFC4652] provides a map between link attributes and characteristics
 and their representation in sub-TLVs of the top-level Link TLV of the
 Opaque TE LSA [RFC3630] and [RFC4203], with the exception of the
 local adaptation (see below).  Advertisement of this information
 SHOULD be supported on a per-layer basis, i.e., one Opaque TE LSA per
 switching capability (and per bandwidth granularity, e.g., low-order
 virtual container and high-order virtual container).

4.1. Local Adaptation

 Local adaptation is defined as a TE link attribute (i.e., sub-TLV)
 that describes the cross/inter-layer relationships.
 The Interface Switching Capability Descriptor (ISCD) TE Attribute
 [RFC4202] identifies the ability of the TE link to support cross-
 connection to another link within the same layer, and the ability to
 use a locally terminated connection that belongs to one layer as a
 data link for another layer (adaptation capability).  However, the
 information associated with the ability to terminate connections
 within that layer (referred to as the termination capability) is
 embedded with the adaptation capability.

Papdimitriou Experimental [Page 8] RFC 5787 ASON Routing for OSPFv2 Protocols March 2010

 For instance, a link between two optical cross-connects will contain
 at least one ISCD attribute describing the lambda switching capable
 (LSC) switching capability; whereas a link between an optical cross-
 connect and an IP/MPLS LSR will contain at least two ISCD attributes:
 one for the description of the LSC termination capability and one for
 the packet switching capable (PSC) adaptation capability.
 In OSPFv2, the Interface Switching Capability Descriptor (ISCD) is a
 sub-TLV (of type 15) of the top-level Link TLV (of type 2) [RFC4203].
 The adaptation and termination capabilities are advertised using two
 separate ISCD sub-TLVs within the same top-level Link TLV.
 Per [RFC4202] and [RFC4203], an interface MAY have more than one ISCD
 sub-TLV.  Hence, the corresponding advertisements should not result
 in any compatibility issues.
 Further refinement of the ISCD sub-TLV for multi-layer networks is
 outside the scope of this document.

4.2. Bandwidth Accounting

 GMPLS routing defines an Interface Switching Capability Descriptor
 (ISCD) that delivers, among other things, information about the
 (maximum/minimum) bandwidth per priority that a Label Switched Path
 (LSP) can make use of.  Per [RFC4202] and [RFC4203], one or more ISCD
 sub-TLVs can be associated with an interface.  This information,
 combined with the Unreserved Bandwidth (sub-TLV defined in [RFC3630],
 Section 2.5.8), provides the basis for bandwidth accounting.
 In the ASON context, additional information may be included when the
 representation and information in the other advertised fields are not
 sufficient for a specific technology (e.g., SDH).  The definition of
 technology-specific information elements is beyond the scope of this
 document.  Some technologies will not require additional information
 beyond what is already defined in [RFC3630], [RFC4202], and
 [RFC4203].

5. Routing Information Scope

5.1. Terminology and Identification

 The definition of short-hand terminology introduced in [RFC4652] is
 repeated here for clarity.
  1. Pi is a physical (bearer/data/transport plane) node.

Papdimitriou Experimental [Page 9] RFC 5787 ASON Routing for OSPFv2 Protocols March 2010

  1. Li is a logical control plane entity that is associated to a single

data plane (abstract) node. Each Li is identified by a unique TE

   Router ID.  The latter is a control plane identifier, defined as
   the Router Address top-level TLV of the Type 1 TE LSA [RFC3630].
   Note: The Router Address top-level TLV definition, processing, and
   usage remain per [RFC3630].  This TLV specifies a stable IP address
   of the advertising router (Ri) that is always reachable if there is
   any IP connectivity to it (e.g., via the Data Communication
   Network).  Moreover, each advertising router advertises a unique,
   reachable IP address for each Pi on behalf of which it makes
   advertisements.
  1. Ri is a logical control plane entity that is associated to a

control plane "router". The latter is the source for topology

   information that it generates and shares with other control plane
   "routers".  The Ri is identified by the (advertising) Router ID
   (32-bit) [RFC2328].
   The Router ID, which is represented by Ri and which corresponds to
   the RC-ID [RFC4258], does not enter into the identification of the
   logical entities representing the data plane resources such as
   links.  The Routing Database (RDB) is associated to the Ri.
 Note: Aside from the Li/Pi mappings, these identifiers are not
 assumed to be in a particular entity relationship except that the Ri
 may have multiple Lis in its scope.  The relationship between Ri and
 Li is simple at any moment in time: an Li may be advertised by only
 one Ri at any time.  However, an Ri may advertise a set of one or
 more Lis.  Hence, the OSPFv2 routing protocol must support a single
 Ri advertising on behalf of more than one Li.

5.2. Link Advertisement (Local and Remote TE Router ID Sub-TLV)

 A Router ID (Ri) advertising on behalf multiple TE Router IDs (Lis)
 creates a 1:N relationship between the Router ID and the TE Router
 ID.  As the link local and link remote (unnumbered) ID association is
 not unique per node (per Li unicity), the advertisement needs to
 indicate the remote Lj value and rely on the initial discovery
 process to retrieve the [Li;Lj] relationship.  In brief, as
 unnumbered links have their ID defined on a per-Li basis, the remote
 Lj needs to be identified to scope the link remote ID to the local
 Li.  Therefore, the routing protocol MUST be able to disambiguate the
 advertised TE links so that they can be associated with the correct
 TE Router ID.

Papdimitriou Experimental [Page 10] RFC 5787 ASON Routing for OSPFv2 Protocols March 2010

 For this purpose, a new sub-TLV of the (OSPFv2 TE LSA) top-level Link
 TLV is introduced that defines the Local and Remote TE Router ID.
 The Type field of the Local and Remote TE Router ID sub-TLV is
 assigned a value in the range 32768-32777 agreed to by all
 participants in the experiment.  The Length field takes the value 8.
 The Value field of this sub-TLV contains 4 octets of the Local TE
 Router Identifier followed by 4 octets of the Remote TE Router
 Identifier.  The value of the Local and Remote TE Router Identifier
 SHOULD NOT be set to 0.
 The format of the Local and Remote TE Router ID sub-TLV is:
  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 (8)           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                 Local TE Router Identifier                    |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                 Remote TE Router Identifier                   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 This sub-TLV is only required to be included as part of the top-level
 Link TLV if the Router ID is advertising on behalf of more than one
 TE Router ID.  In any other case, this sub-TLV SHOULD be omitted
 except if the operator plans to start off with 1 Li and progressively
 add more Lis (under the same Ri) such as to maintain consistency.
 Note: The Link ID sub-TLV that identifies the other end of the link
 (i.e., Router ID of the neighbor for point-to-point links) MUST
 appear exactly once per Link TLV.  This sub-TLV MUST be processed as
 defined in [RFC3630].

5.3. Reachability Advertisement (Local TE Router ID sub-TLV)

 When the Router ID is advertised on behalf of multiple TE Router IDs
 (Lis), the routing protocol MUST be able to associate the advertised
 reachability information with the correct TE Router ID.
 For this purpose, a new sub-TLV of the (OSPFv2 TE LSA) top-level Node
 Attribute TLV is introduced.  This TLV associates the local prefixes
 (see above) to a given TE Router ID.

Papdimitriou Experimental [Page 11] RFC 5787 ASON Routing for OSPFv2 Protocols March 2010

 The Type field of the Local TE Router ID sub-TLV is assigned a value
 in the range 32768-32777 agreed to by all participants in the
 experiment.  The Length field takes the value 4.  The Value field of
 this sub-TLV contains the Local TE Router Identifier [RFC3630]
 encoded over 4 octets.
 The format of the Local TE Router ID sub-TLV is:
  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 (4)           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                 Local TE Router Identifier                    |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 This sub-TLV is only required to be included as part of the Node
 Attribute TLV if the Router ID is advertising on behalf of more than
 one TE Router ID.  In any other case, this sub-TLV SHOULD be omitted.

6. Routing Information Dissemination

 An ASON routing area (RA) represents a partition of the data plane,
 and its identifier is used within the control plane as the
 representation of this partition.  An RA may contain smaller RAs
 inter-connected by links.  The limit of the subdivision results is an
 RA that contains two sub-networks interconnected by a single link.
 ASON RA levels do not reflect routing protocol levels (such as OSPF
 areas).
 Successive hierarchical levels of RAs can be represented by separate
 instances of the protocol.
 Routing controllers (RCs) supporting RAs disseminate information
 downward and upward in this hierarchy.  The vertical routing
 information dissemination mechanisms described in this section do not
 introduce or imply a new OSPF routing area hierarchy.  RCs supporting
 RAs at multiple levels are structured as separate OSPF instances with
 routing information exchanges between levels described by import and
 export rules operating between OSPF instances.
 The implication is that an RC that performs import/export of routing
 information as described in this document does not implement an Area
 Border Router (ABR) functionality.

Papdimitriou Experimental [Page 12] RFC 5787 ASON Routing for OSPFv2 Protocols March 2010

6.1. Import/Export Rules

 RCs supporting RAs disseminate information upward and downward in the
 hierarchy by importing/exporting routing information as Opaque TE
 LSAs (Opaque Type 1) of LS Type 10.  The information that MAY be
 exchanged between adjacent levels includes the Router Address, Link,
 and Node Attribute top-level TLVs.
 The Opaque TE LSA import/export rules are governed as follows:
  1. If the export target interface is associated with the same RA as is

associated with the import interface, the Opaque LSA MUST NOT be

   imported.
  1. If a match is found between the advertising Router ID in the header

of the received Opaque TE LSA and one of the Router IDs belonging

   to the RA of the export target interface, the Opaque LSA MUST NOT
   be imported.
  1. If these two conditions are not met, the Opaque TE LSA MAY be

imported according to local policy. If imported, the LSA MAY be

   disseminated according to local policy.  If disseminated, the
   normal OSPF flooding rules MUST be followed and the advertising
   Router ID MUST be set to the importing router's Router ID.
 The imported/exported routing information content MAY be transformed,
 e.g., filtered or aggregated, as long as the resulting routing
 information is consistent.  In particular, when more than one RC is
 bound to adjacent levels and both are allowed to import/export
 routing information, it is expected that these transformations are
 performed in a consistent manner.  Definition of these policy-based
 mechanisms is outside the scope of this document.
 In practice, and in order to avoid scalability and processing
 overhead, routing information imported/exported downward/upward in
 the hierarchy is expected to include reachability information (see
 Section 3) and, upon strict policy control, link topology
 information.

6.2 Discovery and Selection

6.2.1. Upward Discovery and Selection

 In order to discover RCs that are capable of disseminating routing
 information up the routing hierarchy, the following capability
 descriptor bit is set in the OSPF Router Information Experimental
 Capabilities TLV (see Section 6.2.3) carried in the Router
 Information LSA ([RFC4970]).

Papdimitriou Experimental [Page 13] RFC 5787 ASON Routing for OSPFv2 Protocols March 2010

  1. U bit: When set, this flag indicates that the RC is capable of

disseminating routing information upward to the adjacent level.

 In the case that multiple RCs are advertised from the same RA with
 their U bit set, the RC with the highest Router ID, among those RCs
 with the U bit set, SHOULD be selected as the RC for upward
 dissemination of routing information.  The other RCs MUST NOT
 participate in the upward dissemination of routing information as
 long as the Opaque LSA information corresponding to the highest
 Router ID RC does not reach MaxAge.  This mechanism prevents more
 than one RC advertising routing information upward in the routing
 hierarchy from the same RA.
 Note that if the information to allow the selection of the RC that
 will be used to disseminate routing information up the hierarchy from
 a specific RA cannot be discovered automatically, it MUST be manually
 configured.
 Once an RC has been selected, it remains unmodified even if an RC
 with a higher Router ID is introduced and advertises its capability
 to disseminate routing information upward the adjacent level (i.e., U
 bit set).  This hysteresis mechanism prevents from disturbing the
 upward routing information dissemination process in case, e.g., of
 flapping.

6.2.2. Downward Discovery and Selection

 The same discovery mechanism is used for selecting the RC responsible
 for dissemination of routing information downward in the hierarchy.
 However, an additional restriction MUST be applied such that the RC
 selection process takes into account that an upper level may be
 adjacent to one or more lower (RA) levels.  For this purpose, a
 specific TLV indexing the (lower) RA ID to which the RCs are capable
 of disseminating routing information is needed.
 The Downstream Associated RA ID TLV is carried in the OSPF Router
 Information LSA [RFC4970].  The Type field of the Downstream
 Associated RA ID TLV is assigned a value in the range 32768-32777
 agreed to by all participants in the experiment.  The Length of this
 TLV is n x 4 octets.  The Value field of this sub-TLV contains the
 list of Associated RA IDs.  Each Associated RA ID value is encoded
 following the OSPF area ID (32 bits) encoding rules defined in
 [RFC2328].

Papdimitriou Experimental [Page 14] RFC 5787 ASON Routing for OSPFv2 Protocols March 2010

 The format of the Downstream Associated RA ID TLV is:
  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 (4 x n)        |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                     Associated RA ID 1                        |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 //                             ...                              //
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                     Associated RA ID n                        |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 To discover RCs that are capable of disseminating routing information
 downward through the routing hierarchy, the following capability
 descriptor bit is set in the OSPF Router Information Experimental
 Capabilities TLV (see Section 6.2.3) carried in the Router
 Information LSA ([RFC4970]).
 Note that the Downstream Associated RA ID TLV MUST be present when
 the D bit is set.
  1. D bit: when set, this flag indicates that the RC is capable of

disseminating routing information downward to the adjacent levels.

 If multiple RCs are advertised for the same Associated RA ID, the RC
 with the highest Router ID, among the RCs with the D bit set, MUST be
 selected as the RC for downward dissemination of routing information.
 The other RCs for the same Associated RA ID MUST NOT participate in
 the downward dissemination of routing information as long as the
 Opaque LSA information corresponding to the highest Router ID RC does
 not reach MaxAge.  This mechanism prevents more than one RC from
 advertising routing information downward through the routing
 hierarchy.
 Note that if the information to allow the selection of the RC that
 will be used to disseminate routing information down the hierarchy to
 a specific RA cannot be discovered automatically, it MUST be manually
 configured.
 The OSPF Router information Opaque LSA (Opaque type of 4, Opaque ID
 of 0) and its content, in particular the Router Informational
 Capabilities TLV [RFC4970] and TE Node Capability Descriptor TLV
 [RFC5073], MUST NOT be re-originated.

Papdimitriou Experimental [Page 15] RFC 5787 ASON Routing for OSPFv2 Protocols March 2010

6.2.3. Router Information Experimental Capabilities TLV

 A new TLV is defined for inclusion in the Router Information LSA to
 carry experimental capabilities because the assignment policy for
 bits in the Router Informational Capabilities TLV is "Standards
 Action" [RFC5226] prohibiting its use from Experimental documents.
 The format of the Router Information Experimental Capabilities 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             |             Length            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |             Experimental Capabilities                         |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    Type     A value in the range 32768-32777 agreed to by all
             participants in the experiment.
    Length   A 16-bit field that indicates the length of the value
             portion in octets and will be a multiple of 4 octets
             dependent on the number of capabilities advertised.
             Initially, the length will be 4, denoting 4 octets of
             informational capability bits.
    Value    A variable-length sequence of capability bits rounded to
             a multiple of 4 octets padded with undefined bits.
 The following experimental capability bits are assigned:
    Bit       Capabilities
    0         The U bit (see Section 6.2.1)
    1         The D bit (see Section 6.2.2)

6.3. Loop Prevention

 When more than one RC is bound to an adjacent level of the hierarchy,
 and is configured or selected to redistribute routing information
 upward and downward, a specific mechanism is required to avoid
 looping of routing information.  Looping is the re-introduction of
 routing information that has been advertised from the upper level
 back to the upper level.  This specific case occurs, for example,
 when the RC advertising routing information downward in the hierarchy
 is not the same one that advertises routing upward in the hierarchy.

Papdimitriou Experimental [Page 16] RFC 5787 ASON Routing for OSPFv2 Protocols March 2010

 When these conditions are met, it is necessary to have a means by
 which an RC receiving an Opaque TE LSA imported/exported downward by
 an RC associated to the same RA does not import/export the content of
 this LSA back upward into the (same) upper level.
 Note that configuration and operational simplification can be
 obtained when both functionalities are configured on a single RC (per
 pair of adjacent levels) fulfilling both roles.  Figure 1 provides an
 example where such simplification applies.
            ....................................................
            .                                                  .
            .            RC_5 ------------ RC_6                .
            .             |                 |                  .
            .             |                 |            RA_Y  .
   Upper    .           *********         *********            .
   Layer    ............* RC_1a *.........* RC_2a *.............
      __________________* |     *_________* |     *__________________
            ............* RC_1b *...   ...* RC 2b *.............
   Lower    .           *********  .   .  *********            .
   Layer    .             |        .   .    |                  .
            .  RA_Z       |        .   .    |            RA_X  .
            .            RC_3      .   .   RC_4                .
            .                      .   .                       .
            ........................   .........................
             Figure 1.  Hierarchical Environment (Example)
 In this case, the procedure described in this section MAY be omitted,
 as long as these conditions are permanently guaranteed.  In all other
 cases, without exception, the procedure described in this section
 MUST be applied.

6.3.1. Associated RA ID

 We need some way of filtering the downward/upward re-originated
 Opaque TE LSA.  Per [RFC5250], the information contained in Opaque
 LSAs may be used directly by OSPF.  By adding the RA ID associated
 with the incoming routing information, the loop prevention problem
 can be solved.
 This additional information, referred to as the Associated RA ID, MAY
 be carried in Opaque LSAs that include any of the following top-level
 TLVs:
  1. Router Address top-level TLV
  2. Link top-level TLV
  3. Node Attribute top-level TLV

Papdimitriou Experimental [Page 17] RFC 5787 ASON Routing for OSPFv2 Protocols March 2010

 The Associated RA ID reflects the identifier of the area from which
 the routing information is received.  For example, for a multi-level
 hierarchy, this identifier does not reflect the originating RA ID; it
 will reflect the RA from which the routing information is imported.
 The Type field of the Associated RA ID sub-TLV is assigned a value in
 the range 32768-32777 agreed to by all participants in the
 experiment.  The same value MUST be used for the Type regardless of
 which TLV the sub-TLV appears in.
 The Length of the Associated RA ID TLV is 4 octets.  The Value field
 of this sub-TLV contains the Associated RA ID.  The Associated RA ID
 value is encoded following the OSPF area ID (32 bits) encoding rules
 defined in [RFC2328].
 The format of the Associated RA ID TLV is defined 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             |           Length (4)          |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                       Associated RA ID                        |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

6.3.2. Processing

 When fulfilling the rules detailed in Section 6.1, a given Opaque LSA
 is imported/exported downward or upward the routing hierarchy, and
 the Associated RA ID TLV is added to the received Opaque LSA list of
 TLVs such as to identify the area from which this routing information
 has been received.
 When the RC adjacent to the lower or upper routing level receives
 this Opaque LSA, the following rule is applied (in addition to the
 rule governing the import/export of Opaque LSAs as detailed in
 Section 6.1).
  1. If a match is found between the Associated RA ID of the received

Opaque TE LSA and the RA ID belonging to the area of the export

   target interface, the Opaque TE LSA MUST NOT be imported.
  1. Otherwise, this Opaque LSA MAY be imported and disseminated

downward or upward the routing hierarchy following the OSPF

   flooding rules.
 This mechanism ensures that no race condition occurs when the
 conditions depicted in Figure 2 are met.

Papdimitriou Experimental [Page 18] RFC 5787 ASON Routing for OSPFv2 Protocols March 2010

                         RC_5 ------------- RC_6
                          |                 |
                          |                 |            RA_Y
   Upper                *********         *********
   Layer    ............* RC_1a *.........* RC_2a *.............
      __________________* |     *_________* |     *__________________
            ............* RC_1b *.........* RC_2b *.............
   Lower                *********         *********
   Layer                  |                 |
                          |                 |            RA_X
                         RC_3 --- . . . --- RC_4
             Figure 2.  Race Condition Prevention (Example)
 Assume that RC_1b is configured for exporting routing information
 upward toward RA_Y (upward the routing hierarchy) and that RC_2a is
 configured for exporting routing information toward RA_X (downward
 the routing hierarchy).
 Assume that routing information advertised by RC_3 would reach RC_4
 faster across RA_Y through hierarchy.
 If RC_2b is not able to prevent from importing that information, RC_4
 may receive that information before the same advertisement would
 propagate in RA_X (from RC_3) to RC_4.  For this purpose, RC_1a
 inserts the Associated RA X to the imported routing information from
 RA_X.  Because RC_2b finds a match between the Associated RA ID (X)
 of the received Opaque TE LSA and the ID (X) of the RA of the export
 target interface, this LSA MUST NOT be imported.

6.4. Resiliency

 OSPF creates adjacencies between neighboring routers for the purpose
 of exchanging routing information.  After a neighbor has been
 discovered, bidirectional communication is ensured, and a routing
 adjacency is formed between RCs, loss of communication may result in
 partitioned OSPF areas and so in partitioned RAs.
 Consider for instance (see Figure 2) the case where RC_1a and RC_1b
 are configured for exchanging routing information downward and upward
 RA_Y, respectively, and that RC_2a and RC_2b are not configured for
 exchanging any routing information toward RA_X.  If the communication
 between RC_1a and RC_2a is broken (due, e.g., to RC_5 - RC_6
 communication failure), RA_Y could be partitioned.
 In these conditions, it is RECOMMENDED that RC_2a be re-configurable
 such as to allow for exchanging routing information downward to RA_X.
 This reconfiguration MAY be performed manually or automatically.  In

Papdimitriou Experimental [Page 19] RFC 5787 ASON Routing for OSPFv2 Protocols March 2010

 the latter cases, automatic reconfiguration uses the mechanism
 described in Section 6.2 (forcing MaxAge of the corresponding opaque
 LSA information in case the originating RC becomes unreachable).
 Manual reconfiguration MUST be supported.

6.5. Neighbor Relationship and Routing Adjacency

 It is assumed that (point-to-point) IP control channels are
 provisioned/configured between RCs belonging to the same routing
 level.  Provisioning/configuration techniques are outside the scope
 of this document.
 Once established, the OSPF Hello protocol is responsible for
 establishing and maintaining neighbor relationships.  This protocol
 also ensures that communication between neighbors is bidirectional.
 Routing adjacency can subsequently be formed between RCs following
 mechanisms defined in [RFC2328].

6.6 Reconfiguration

 This section details the RA ID reconfiguration steps.
 Reconfiguration of the RA ID occurs when the RA ID is modified, e.g.,
 from value Z to value X or Y (see Figure 2).
 The process of reconfiguring the RA ID involves:
  1. Disable the import/export of routing information from the upper and

lower levels (to prevent any LS information update).

  1. Change the RA ID of the local level RA from, e.g., Z to X or Y.

Perform a Link State Database (LSDB) checksum on all routers to

   verify that LSDBs are consistent.
  1. Enable import of upstream and downstream routing information such

as to re-synchronize local-level LSDBs from any LS information that

   may have occurred in an upper or a lower routing level.
  1. Enable export of routing information downstream such as to re-sync

the downstream level with the newly reconfigured RA ID (as part of

   the re-advertised Opaque TE LSA).
  1. Enable export of routing information upstream such as to re-sync

the upstream level with the newly reconfigured RA ID (as part of

   the re-advertised Opaque TE LSA).
 Note that the re-sync operation needs to be carried out only between
 the directly adjacent upper and lower routing levels.

Papdimitriou Experimental [Page 20] RFC 5787 ASON Routing for OSPFv2 Protocols March 2010

7. OSPFv2 Scalability

  1. Routing information exchange upward/downward in the hierarchy

between adjacent RAs SHOULD by default be limited to reachability

   information.  In addition, several transformations such as prefix
   aggregation are RECOMMENDED when allowing the amount of information
   imported/exported by a given RC to be decreased without impacting
   consistency.
  1. Routing information exchange upward/downward in the hierarchy

involving TE attributes MUST be under strict policy control.

   Pacing and min/max thresholds for triggered updates are strongly
   RECOMMENDED.
  1. The number of routing levels MUST be maintained under strict policy

control.

8. Security Considerations

 This document specifies the contents and processing of Opaque LSAs in
 OSPFv2 [RFC2328].  Opaque TE and RI LSAs defined in this document are
 not used for SPF computation, and so have no direct effect on IP
 routing.  Additionally, ASON routing domains are delimited by the
 usual administrative domain boundaries.
 Any mechanisms used for securing the exchange of normal OSPF LSAs can
 be applied equally to all Opaque TE and RI LSAs used in the ASON
 context.  Authentication of OSPFv2 LSA exchanges (such as OSPF
 cryptographic authentication [RFC2328] and [RFC5709]) can be used to
 secure against passive attacks and provide significant protection
 against active attacks.  [RFC5709] defines a mechanism for
 authenticating OSPF packets by making use of the HMAC algorithm in
 conjunction with the SHA family of cryptographic hash functions.
 [RFC2154] adds 1) digital signatures to authenticate OSPF LSA data,
 2) a certification mechanism for distribution of routing information,
 and 3) a neighbor-to-neighbor authentication algorithm to protect
 local OSPFv2 protocol exchanges.

9. Experimental Code Points

 This document is classified as Experimental.  It defines new TLVs and
 sub-TLVs for inclusion in OSPF LSAs.  According to the assignment
 policies for the registries of code points for these TLVs and sub-
 TLVs, values must be assigned from the experimental ranges and must
 not be recorded by IANA or mentioned in this document.
 The following sections summarize the TLVs and sub-TLVs concerned.

Papdimitriou Experimental [Page 21] RFC 5787 ASON Routing for OSPFv2 Protocols March 2010

9.1. Sub-TLVs of the Link TLV

 This document defines the following sub-TLVs of the Link TLV carried
 in the OSPF TE LSA:
  1. Local and Remote TE Router ID sub-TLV
  2. Associated RA ID sub-TLV
 The defining text for code point assignment for sub-TLVs of the OSPF
 TE Link TLV says ([RFC3630]):
    o  Types in the range 10-32767 are to be assigned via Standards
       Action.
    o  Types in the range 32768-32777 are for experimental use; these
       will not be registered with IANA, and MUST NOT be mentioned by
       RFCs.
    o  Types in the range 32778-65535 are not to be assigned at this
       time.
 That means that the new sub-TLVs must be assigned type values from
 the range 32768-32777.  It is a matter for experimental
 implementations to assign their own code points, and to agree with
 cooperating implementations participating in the same experiments
 what values to use.
 Note that the same value for the Associated RA ID sub-TLV MUST be
 used when it appears in the Link TLV, the Node Attribute TLV, and the
 Router Address TLV.

9.2. Sub-TLVs of the Node Attribute TLV

 This document defines the following sub-TLVs of the Node Attribute
 TLV carried in the OSPF TE LSA.
  1. Node IPv4 Local Prefix sub-TLV
  2. Node IPv6 Local Prefix sub-TLV
  3. Local TE Router ID sub-TLV
  4. Associated RA ID sub-TLV
 The defining text for code point assignment for sub-TLVs of the OSPF
 Node Attribute TLV says ([RFC5786]):
    o  Types in the range 3-32767 are to be assigned via Standards
       Action.

Papdimitriou Experimental [Page 22] RFC 5787 ASON Routing for OSPFv2 Protocols March 2010

    o  Types in the range 32768-32777 are for experimental use; these
       will not be registered with IANA, and MUST NOT be mentioned by
       RFCs.
    o  Types in the range 32778-65535 are not to be assigned at this
       time.  Before any assignments can be made in this range, there
       MUST be a Standards Track RFC that specifies IANA
       Considerations that covers the range being assigned.
 That means that the new sub-TLVs must be assigned type values from
 the range 32768-32777.  It is a matter for experimental
 implementations to assign their own code points, and to agree with
 cooperating implementations participating in the same experiments
 what values to use.
 Note that the same value for the Associated RA ID sub-TLV MUST be
 used when it appears in the Link TLV, the Node Attribute TLV, and the
 Router Address TLV.

9.3. Sub-TLVs of the Router Address TLV

 The OSPF Router Address TLV is defined in [RFC3630].  No sub-TLVs are
 defined in that document and there is no registry or allocation
 policy for sub-TLVs of the Router Address TLV.
 This document defines the following new sub-TLV for inclusion in the
 OSPF Router Address TLV:
  1. Associated RA ID sub-TLV
 Note that the same value for the Associated RA ID sub-TLV MUST be
 used when it appears in the Link TLV, the Node Attribute TLV, and the
 Router Address TLV.  This is consistent with potential for a future
 definition of a registry with policies that match the other existing
 registries.

9.4. TLVs of the Router Information LSA

 This document defines two new TLVs to be carried in the Router
 Information LSA.
  1. Downstream Associated RA ID TLV
  2. Router Information Experimental Capabilities TLV
 The defining text for code point assignment for TLVs of the OSPF
 Router Information LSA says ([RFC4970]):
    o  1-32767 Standards Action.

Papdimitriou Experimental [Page 23] RFC 5787 ASON Routing for OSPFv2 Protocols March 2010

    o  Types in the range 32768-32777 are for experimental use; these
       will not be registered with IANA and MUST NOT be mentioned by
       RFCs.
    o  Types in the range 32778-65535 are reserved and are not to be
       assigned at this time.  Before any assignments can be made in
       this range, there MUST be a Standards Track RFC that specifies
       IANA Considerations that covers the range being assigned.
 That means that the new TLVs must be assigned type values from the
 range 32768-32777.  It is a matter for experimental implementations
 to assign their own code points, and to agree with cooperating
 implementations participating in the same experiments what values to
 use.

10. References

10.1. Normative References

 [RFC2119]    Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2154]    Murphy, S., Badger, M., and B. Wellington, "OSPF with
              Digital Signatures", RFC 2154, June 1997.
 [RFC2328]    Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.
 [RFC3630]    Katz, D., Kompella, K., and D. Yeung, "Traffic
              Engineering (TE) Extensions to OSPF Version 2", RFC
              3630, September 2003.
 [RFC3945]    Mannie, E., Ed., "Generalized Multi-Protocol Label
              Switching (GMPLS) Architecture", RFC 3945, October 2004.
 [RFC4202]    Kompella, K., Ed., and Y. Rekhter, Ed., "Routing
              Extensions in Support of Generalized Multi-Protocol
              Label Switching (GMPLS)", RFC 4202, October 2005.
 [RFC4203]    Kompella, K., Ed., and Y. Rekhter, Ed., "OSPF Extensions
              in Support of Generalized Multi-Protocol Label Switching
              (GMPLS)", RFC 4203, October 2005.
 [RFC4970]    Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R.,
              and S. Shaffer, "Extensions to OSPF for Advertising
              Optional Router Capabilities", RFC 4970, July 2007.

Papdimitriou Experimental [Page 24] RFC 5787 ASON Routing for OSPFv2 Protocols March 2010

 [RFC5226]    Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.
 [RFC5250]    Berger, L., Bryskin, I., Zinin, A., and R. Coltun, "The
              OSPF Opaque LSA Option", RFC 5250, July 2008.
 [RFC5340]    Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
              for IPv6", RFC 5340, July 2008.
 [RFC5786]    Aggarwal, R. and K. Kompella, "Advertising a Router's
              Local Addresses in OSPF TE Extensions", RFC 5786, March
              2010.

10.2. Informative References

 [RFC4258]    Brungard, D., Ed., "Requirements for Generalized Multi-
              Protocol Label Switching (GMPLS) Routing for the
              Automatically Switched Optical Network (ASON)", RFC
              4258, November 2005.
 [RFC4652]    Papadimitriou, D., Ed., Ong, L., Sadler, J., Shew, S.,
              and D. Ward, "Evaluation of Existing Routing Protocols
              against Automatic Switched Optical Network (ASON)
              Routing Requirements", RFC 4652, October 2006.
 [RFC5073]    Vasseur, J., Ed., and J. Le Roux, Ed., "IGP Routing
              Protocol Extensions for Discovery of Traffic Engineering
              Node Capabilities", RFC 5073, December 2007.
 [RFC5709]    Bhatia, M., Manral, V., Fanto, M., White, R., Barnes,
              M., Li, T., and R. Atkinson, "OSPFv2 HMAC-SHA
              Cryptographic Authentication", RFC 5709, October 2009.
 For information on the availability of ITU Documents, please see
 http://www.itu.int.
 [G.7715]     ITU-T Rec. G.7715/Y.1306, "Architecture and Requirements
              for the Automatically Switched Optical Network (ASON)",
              June 2002.
 [G.7715.1]   ITU-T Draft Rec. G.7715.1/Y.1706.1, "ASON Routing
              Architecture and Requirements for Link State Protocols",
              November 2003.
 [G.805]      ITU-T Rec. G.805, "Generic functional architecture of
              transport networks)", March 2000.

Papdimitriou Experimental [Page 25] RFC 5787 ASON Routing for OSPFv2 Protocols March 2010

 [G.8080]     ITU-T Rec. G.8080/Y.1304, "Architecture for the
              Automatically Switched Optical Network (ASON)," November
              2001 (and Revision, January 2003).

11. Acknowledgements

 The author would like to thank Dean Cheng, Acee Lindem, Pandian
 Vijay, Alan Davey, Adrian Farrel, Deborah Brungard, and Ben Campbell
 for their useful comments and suggestions.
 Lisa Dusseault and Jari Arkko provided useful comments during IESG
 review.
 Question 14 of Study Group 15 of the ITU-T provided useful and
 constructive input.

Papdimitriou Experimental [Page 26] RFC 5787 ASON Routing for OSPFv2 Protocols March 2010

Appendix A. ASON Terminology

 This document makes use of the following terms:
 Administrative domain: (See Recommendation [G.805].)  For the
    purposes of [G7715.1], an administrative domain represents the
    extent of resources that belong to a single player such as a
    network operator, a service provider, or an end-user.
    Administrative domains of different players do not overlap amongst
    themselves.
 Control plane: performs the call control and connection control
    functions.  Through signaling, the control plane sets up and
    releases connections, and may restore a connection in case of a
    failure.
 (Control) Domain: represents a collection of (control) entities that
    are grouped for a particular purpose.  The control plane is
    subdivided into domains matching administrative domains.  Within
    an administrative domain, further subdivisions of the control
    plane are recursively applied.  A routing control domain is an
    abstract entity that hides the details of the RC distribution.
 External NNI (E-NNI): interfaces are located between protocol
    controllers between control domains.
 Internal NNI (I-NNI): interfaces are located between protocol
    controllers within control domains.
 Link: (See Recommendation G.805.)  A "topological component" that
    describes a fixed relationship between a "subnetwork" or "access
    group" and another "subnetwork" or "access group".  Links are not
    limited to being provided by a single server trail.
 Management plane: performs management functions for the transport
    plane, the control plane, and the system as a whole.  It also
    provides coordination between all the planes.  The following
    management functional areas are performed in the management plane:
    performance, fault, configuration, accounting, and security
    management.
 Management domain: (See Recommendation G.805.)  A management domain
    defines a collection of managed objects that are grouped to meet
    organizational requirements according to geography, technology,
    policy, or other structure, and for a number of functional areas
    such as configuration, security, (FCAPS), for the purpose of
    providing control in a consistent manner.  Management domains can
    be disjoint, contained, or overlapping.  As such, the resources

Papdimitriou Experimental [Page 27] RFC 5787 ASON Routing for OSPFv2 Protocols March 2010

    within an administrative domain can be distributed into several
    possible overlapping management domains.  The same resource can
    therefore belong to several management domains simultaneously, but
    a management domain shall not cross the border of an
    administrative domain.
 Subnetwork Point (SNP): The SNP is a control plane abstraction that
    represents an actual or potential transport plane resource.  SNPs
    (in different subnetwork partitions) may represent the same
    transport resource.  A one-to-one correspondence should not be
    assumed.
 Subnetwork Point Pool (SNPP): A set of SNPs that are grouped together
    for the purposes of routing.
 Termination Connection Point (TCP): A TCP represents the output of a
    Trail Termination function or the input to a Trail Termination
    Sink function.
 Transport plane: provides bidirectional or unidirectional transfer of
    user information, from one location to another.  It can also
    provide transfer of some control and network management
    information.  The transport plane is layered; it is equivalent to
    the Transport Network defined in Recommendation G.805.
 User Network Interface (UNI): interfaces are located between protocol
    controllers between a user and a control domain.  Note: There is
    no routing function associated with a UNI reference point.

Appendix B. ASON Routing Terminology

 This document makes use of the following terms:
 Routing Area (RA): an RA represents a partition of the data plane,
    and its identifier is used within the control plane as the
    representation of this partition.  Per [G.8080], an RA is defined
    by a set of sub-networks, the links that interconnect them, and
    the interfaces representing the ends of the links exiting that RA.
    An RA may contain smaller RAs inter-connected by links.  The limit
    of subdivision results in an RA that contains two sub-networks
    interconnected by a single link.
 Routing Database (RDB): a repository for the local topology, network
    topology, reachability, and other routing information that is
    updated as part of the routing information exchange and may
    additionally contain information that is configured.  The RDB may
    contain routing information for more than one routing area (RA).

Papdimitriou Experimental [Page 28] RFC 5787 ASON Routing for OSPFv2 Protocols March 2010

 Routing Components: ASON routing architecture functions.  These
    functions can be classified as protocol independent (Link Resource
    Manager or LRM, Routing Controller or RC) or protocol specific
    (Protocol Controller or PC).
 Routing Controller (RC): handles (abstract) information needed for
    routing and the routing information exchange with peering RCs by
    operating on the RDB.  The RC has access to a view of the RDB.
    The RC is protocol independent.
 Note: Since the RDB may contain routing information pertaining to
    multiple RAs (and possibly to multiple layer networks), the RCs
    accessing the RDB may share the routing information.
 Link Resource Manager (LRM): supplies all the relevant component and
    TE link information to the RC.  It informs the RC about any state
    changes of the link resources it controls.
 Protocol Controller (PC): handles protocol-specific message exchanges
    according to the reference point over which the information is
    exchanged (e.g., E-NNI, I-NNI), and internal exchanges with the
    RC.  The PC function is protocol dependent.

Author's Address

 Dimitri Papadimitriou
 Alcatel-Lucent Bell
 Copernicuslaan 50
 B-2018 Antwerpen
 Belgium
 Phone: +32 3 2408491
 EMail: dimitri.papadimitriou@alcatel-lucent.be

Papdimitriou Experimental [Page 29]

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