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rfc:rfc2124

Network Working Group P. Amsden Request for Comments: 2124 J. Amweg Category: Informational P. Calato

                                                            S. Bensley
                                                              G. Lyons
                                                Cabletron Systems Inc.
                                                            March 1997
   Cabletron's Light-weight Flow Admission Protocol Specification
                            Version 1.0

Status of this Memo

 This memo provides information for the Internet community.  This memo
 does not specify an Internet standard of any kind.  Distribution of
 this memo is unlimited.

Abstract

 Light-weight Flow Admission Protocol, LFAP, allows an external Flow
 Admission Service (FAS) to manage flow admission at the switch,
 allowing flexible Flow Admission Services to be deployed by a vendor
 or customer without changes to, or undue burden on, the switch.
 Specifically, this document specifies the protocol between the switch
 Connection Control Entity (CCE) and the external FAS. Using LFAP, a
 Flow Admission Service can: allow or disallow flows, define the
 parameters under which a given flow is to operate (operating policy)
 or, redirect the flow to an alternate destination. The FAS may also
 maintain details of current or historical flows for billing, capacity
 planning and other purposes.

Table of Contents

1. Introduction ………………………………………….. 2 2. Message Flows …………………………………………. 3 3. Message Contents and Format …………………………….. 4

   3.1.  IE Formats .............................................    5
   3.2.  Flow Admission Request (FAR) Message ...................   14
   3.3.  Flow Admission Acknowledge (FAA) Message ...............   15
   3.4.  Flow Admission Update (FAU) Message ....................   15
   3.5  Flow Update Notification (FUN) Message ..................   16
   3.6.  Flow Update Acknowledge (FUA) Message ..................   16
   3.7.  Flow Change Request (FCR) Message ......................   17
   3.8.  Flow Change Acknowledge (FCA) Message ..................   17
   3.9.  Administrative Request (AR) Message ....................   18
   3.10.  Administrative Request Acknowledge (ARA) Message ......   18

4. Error Handling ………………………………………… 18

Amsden, et. al. Informational [Page 1] RFC 2124 LFAP March 1997

   4.1.  FAA Related Error Handling .............................   19
   4.2.  FUA Related Error Handling .............................   19
   4.3.  FCA Related Error Handling .............................   19
   4.4.  ARA Related Error Handling .............................   20

5. Security Considerations ………………………………… 20 6. Author's Addresses …………………………………….. 20 7. References ……………………………………………. 21

1. Introduction

 Light-weight Flow Admission Protocol, LFAP, allows an external Flow
 Admission Service (FAS) to manage flow admission at the switch,
 allowing flexible Flow Admission Services to be deployed by a vendor
 or customer without changes to, or undue burden on, the switch. It
 provides a means for network managers, or management systems, to
 establish connection admission parameters for multiple switches in a
 single management domain by configuring policy information and other
 data via a single centralized connection admission control point.
 Specifically, this document specifies the protocol between the switch
 Connection Control Entity (CCE) and the external FAS. Using LFAP, a
 Flow Admission Service can: allow or disallow flows, define the
 parameters under which a given flow is to operate (operating policy)
 or, redirect the flow to an alternate destination. The FAS may also
 maintain details of current or historical flows for billing, capacity
 planning and other purposes.
 A significant advantage of this protocol is that it relieves switch
 vendors from the complexity of policy enforcement under any number of
 policy representation schemes. Similarly, switch configuration
 managers do not need to translate organization-determined policy or
 usage procedures, limitations and guidelines into an arbitrarily
 large set of vendor-specific representations. Finally, use of such a
 scheme makes possible plug-and-play connection management at the
 present time - in the absence of a standardized representation for
 connection policies.
 This document describes the message flow between switch CCE and FAS,
 the messages used and error handling that applies. This constitutes
 the LFAP interface definition.

Amsden, et. al. Informational [Page 2] RFC 2124 LFAP March 1997

2. Message Flows

 Initiating message flows between CCE and FAS entities always
 originate at the switch.  Therefore, the switch is the point at which
 connectivity is originated.  The CCE must have IP reachability using
 some approach described elsewhere (e.g.  [1577] or [LANE]) and an IP
 address for the FAS must be preconfigured at the switch CCE.  The CCE
 establishes TCP connectivity using the registered port number - ###.
 As shown below, Flow Admission Request (FAR) messages are sent by a
 switch's Call Control Entity (CCE) to the Flow Admission Service
 (FAS). These messages are sent when a flow is about to be set up by
 the switch and contain specific information relating to the flow -
 such as flow identifier, source/destination and qualifying
 information about the flow - that may be required to determine the
 admissibility of the flow and any operating policies that apply to
 the flow if it is admitted.
 The FAS responds with a Flow Admission Acknowledge (FAA) message (to
 the CCE) with a status indicating connection admissibility and any
 operating policy information that applies to the flow.  If a FAA
 message contains mandatory operating policies that the switch CCE
 does not understand, the switch would abort the flow using the Flow
 Admission Update (FAU) message.
  ,--------------------.            ,--------------------.
  |        FAS         |            |       Switch       |
  |                    |            |        CCE         |
  `--+----+----+-------'            `------+-----+----+--'
   ^ | ^  ^ |  ^ |  ^ ^              ^ ^  ^ |  ^ |  | ^ |
   | | |  | |  | |  | |     AR       | |  | |  | |  | | |
   | | |  | |  | |  | '--------------' |  | |  | |  | | |
   | | |  | |  | |  |       ARA        |  | |  | |  | | |
   | | |  | |  | |  '------------------'  | |  | |  | | |
   | | |  | |  | |          FUA           | |  | |  | | |
   | | |  | |  | `------------------------' |  | |  | | |
   | | |  | |  |            FUN             |  | |  | | |
   | | |  | |  `----------------------------'  | |  | | |
   | | |  | |               FCR                | |  | | |
   | | |  | `----------------------------------' |  | | |
   | | |  |                 FCA                  |  | | |
   | | |  `--------------------------------------'  | | |
   | | |                    FAU                     | | |
   | | '--------------------------------------------' | |
   | |                      FAA                       | |
   | `------------------------------------------------' |
   |                        FAR                         |
   `----------------------------------------------------'

Amsden, et. al. Informational [Page 3] RFC 2124 LFAP March 1997

 When a connection is established, periodically during the course of
 maintaining the connection and when a change in connection state
 occurs, the switch CCE sends a Flow Update Notification (FUN) message
 to the FAS.  The FAS, in turn, responds with a Flow Update
 Acknowledge (FUA) message with a Flow failure code if a an error
 condition has been detected. An example of error conditions would be
 receipt of a FUN message indicating octets received and sent for a
 connection never admitted.
 The FAS may send a Flow Change Request (FCR) to the CCE either to
 effect a change in the state of a specific connection or to set any
 new/changed policy information that applies to the flow.
 The CCE replies with a Flow Change Acknowledge (FCA) message and may
 respond  with a flow failure code indicating the offending flow or
 policy change.
 Either the CCE or the FAS may initiate a Administrative Request (AR).
 The CCE uses it to get a Flow Identifier Prefix. The FAS uses it to
 request FUN messages be returned on some set of flows.
 The requested entity (FAS or CCE) replies with a Administrative
 Request Acknowledge. The FAS uses the ARA to return the requested
 Flow Prefix. The CCE uses the ARA to return any Flow Identifiers that
 were in error on the AR.

3. Message Contents and Format

 LFAP defines nine messages: "Flow Admission Request", "Flow Admission
 Acknowledge", "Flow Admission Update", "Flow Update Notification",
 "Flow Update Acknowledge", "Flow Change Request", "Flow Change
 Acknowledge", "Administrative Request" and "Administrative Request
 Acknowledge" (FAR, FAA, FAU, FUN, FUA, FCR, FCA, AR, ARA
 respectively).
 FAR messages are sent by a switch call control entity (CCE) to the
 Flow Admission Service (FAS). FAA messages are responses from the FAS
 to the CCE. FUA messages are responses from the CCE only under error
 conditions. FUN messages originate at switches and are acknowledged
 by FUA messages from the FAS. FCR messages are sent by the FAS to the
 CCE and are acknowledged by FCA messages. AR messages are sent by
 either the Entity (FAS or CCE) and are acknowledged by the ARA
 messages.

Amsden, et. al. Informational [Page 4] RFC 2124 LFAP March 1997

  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    |    Op Code    |   Reserved    |    Status     |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |          Message ID           |         Message Length        |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 ~                 Information Element (IE) Fields               ~
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 The general message format for all LFAP messages is as shown above.
 Version is 1 and Op Codes are as follows:
           FAR - 1
           FAA - 2
           FAU - 3
           FUN - 4
           FUA - 5
           FCR - 6
           FCA - 7
           AR  - 8
           ARA - 9
 The Status field serves as a Status on the overall message. The
 values that Status may assume are:
        STATUS:
           SUCCESS   = 0
           CORRUPTED = 1
           VERSION   = 2
 Message ID is used to associate each original message with its
 corresponding response and must be unique for the combination of
 sender and responder while an original message is pending. The
 Message Length excludes the 8 octets of the message header.

3.1. IE Formats

 IE fields consist of 2-octet TYPE, 2-octet LENGTH and a variable
 length VALUE sub-fields. All IEs are even multiples of 4 octets in
 length, left-aligned and zero filled if necessary. Length is computed
 excluding the 4 octet TYPE and LENGTH fields.
 Individual IEs are formated as described in following sections.

Amsden, et. al. Informational [Page 5] RFC 2124 LFAP March 1997

Byte Count IE

 Contains the count of octets sent and received associated with the
 identified connection. IE format 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 = 1 or 2         |          LENGTH = 16          |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 +-+-+-+-+-                Bytes Received               -+-+-+-+-+
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 +-+-+-+-+-                  Bytes Sent                 -+-+-+-+-+
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 Type 1 Means that the byte count is a running counter and is the
        count from the beginning of the flow establishment.
 Type 2 Means that the byte count is a delta counter and is the
        count since the last FUN message.

Packet Count IE

 Contains the count of packets cells or frames sent and received
 associated with the identified connection. IE format 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 = 3 or 4         |          LENGTH = 16          |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 +-+-+-+-+-        Packets/Cells/Frames Received        -+-+-+-+-+
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 +-+-+-+-+-          Packets/Cells/Frames Sent          -+-+-+-+-+
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 Type 3 Means that the packet/cell/frame count is a running counter
        and is the count from the beginning of the flow establishment.
 Type 4 Means that the packet/cell/frame count is a delta counter
        and is the count since the last FUN message.

Amsden, et. al. Informational [Page 6] RFC 2124 LFAP March 1997

Client Data IE

 For use in determination of admission policy relative to a specific
 connection request based on arbitrary client data (OCTET STRING
 [8824]).  IE format 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 = 5            |            LENGTH             |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 ~                           Client Data                         ~
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Destination Address IE

 Destination address associated with a message. IE format 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 = 6            |             LENGTH            |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |     Address Family Number     |         Address Length        |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 ~                             Address                           ~
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 The Address Length field contains the length of the address excluding
 any pad of zeros used to align the address field.
    Address Family Numbers include:
        1 - 14 (decimal) as specified in [1700]
        15               E.164 with NSAP format subaddress

Flow ID IE

 In order to accumulate the flow accounting statistics across multiple
 FAS's in case of a FAS failure a globally unique flow identifier
 needs to be formed.  To accomplish this the FAS assigns a prefix if
 requested by the CCE.  The CCE then assigns a CCE flow identifier
 that it guaranties to be unique for the use of the FAS flow
 identifier prefix for each flow admitted.  If the CCE needs to reuse

Amsden, et. al. Informational [Page 7] RFC 2124 LFAP March 1997

 a CCE flow ID it must acquire a new FAS prefix.  If a CCE cannot
 support the FAS flow identifier then it does not request a FAS prefix
 and uses a FAS length of 0 in all updates to the flow.  If the CCE
 does not support the FAS identifier prefix then when a CCE fails over
 all calls will need to be readmitted and will be seen as two separate
 calls at the accumulation point.  Flow ID IE is copied exactly in all
 messages that refer to this flow.  IE format 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 = 7            |FAS Length = 8 |CCE Length = 4 |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 |+-+-+-+-+-   FAS assigned Flow Identifier Prefix      -+-+-+-+-+
 |                                                               |
 +-+-+-+-+-+-+-+-+                              +-+-+-+--+-+-+-+-+
 |                 CCE assigned Flow Identifier                  |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Flow State IE

 Flow state is the intended end state for the Flow associated with the
 message containing this IE. IE format 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 = 8            |          LENGTH = 4           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                          Flow State                           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    Flow state has one of the following values and meanings:
        0 - INACTIVE    - Flow is inactive
        1 - ACTIVE      - Flow is active

Policy IE's

 There are two basic types of Policy IE's Optional and Mandatory. In
 the case of optional operating policy if the combination of policy
 and value given cannot be interpreted by a switch CCE it may be
 safely ignored. In the case of mandatory operating policy if the
 combination of policy and value given cannot be interpreted by a
 switch CCE it must abort the flow state. Examples of optional
 operating policies are Checkpoint Timer and Connection Priority.

Amsden, et. al. Informational [Page 8] RFC 2124 LFAP March 1997

 There are also two forms of the policy ID. The first is where the
 policy ID is a number and the second is where the policy ID is an
 Object Identifier. The policy ID's with number values are identified
 in this document and its proposed changes over time. The Object
 Identifier IDs can be used by individual implementers to apply
 proprietary or experimental additions to this document and still be
 compliant with the general form of this document.
 Operating Policy IEs are comprised of Policy ID, a length and a
 value. In the case of the policies defined in this document a length
 is required and specified here. In the case of policies using the OID
 format the length may be implied by the OID or be part of the policy
 value as determined by individual implementation.

Policy IE format for Policy ID's defined in this document

  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 = 9 + 10       |             LENGTH            |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |           Policy ID           |    Policy Value length        |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |                                                               |
 ~                          Policy Value                         ~
 |                                                               |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 ~                   Additional Policy Pairs                     ~
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 Type 9 is an Optional Policy and type 10 is a Mandatory Policy.
 The following policy ID's and policy values are presently defined or
 under consideration.
Policy               ID         Value    Meaning
Usage               01xx                 The purpose of this set of
                                         policies is for usage
                                         constraints. This set of
                                         policies in the future may
                                         include Connection Count,
                                         Maximum Bandwidth and Connect
                                         Time.

Amsden, et. al. Informational [Page 9] RFC 2124 LFAP March 1997

Routing             02xx                 The purpose of these polices
                                         is to allow for various
                                         routing policies to be
                                         enforced in the a switching
                                         environment. This set of
                                         policies may include
                                         Optimization, Designated
                                         Transit List, Restricted
                                         Transit List and Path Cost.
 Administrative      03xx
   Keep Statistics  0301       = 0       Keep statistics on this flow
                               Not= 0    Do Not keep statistics on flow
   Connection       0302       1 - 255   Priority of this connection
       Priority                          Less is higher
   Checkpoint       0303       1 - 2^31  Seconds between FUN on a flow
       Timer
   Checkpoint
       Threshold    0304       1 - 2^63  # of bytes to collect before
                                         sending a FUN on a flow
Connectionless      04xx                 The purpose of these policies
                                         is to control connection
                                         unaware calls. This set will
                                         include Inactivity Timer and
                                         Bandwidth allocation.

Policy IE format when Policy ID is a Object Identifier

  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 = 11 + 12        |             LENGTH            |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 ~                           Policy OID                          ~
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 ~                            Policy                             ~
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 ~                   Additional Policy Pairs                     ~
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 Type 11 is an optional policy and type 12 is a mandatory policy.

Amsden, et. al. Informational [Page 10] RFC 2124 LFAP March 1997

Service Identifier IE

 Used in determination of admission policy relative to a specific
 connection request based on service type. Service Identifier is
 specified as an OCTET STRING [8824].
  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 = 13           |             LENGTH            |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 ~                      Service Identifier                       ~
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Source Address IE

 Source address associated with a message. TYPE is 14, format is as
 shown for Destination Address IE.

Source Switch Address IE

 Source Switch address associated with a message. TYPE is 15, format
 is as shown for Destination Address IE.

Destination Switch Address IE

 Destination Switch address associated with a message. TYPE is 16,
 format is as shown for Destination Address IE.

Time IE

 The time (as a SNMPv2 TimeStamp [1443]) associated with the
 status/statistics observed. TYPE is 17 and format 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 = 17           |          LENGTH = 4           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                              Time                             |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Amsden, et. al. Informational [Page 11] RFC 2124 LFAP March 1997

Multiple Record IE

 The Multiple Record IE is composed of 4 parts.  The record
 descriptor, fixed information, record format IEs and individual
 records.  The record descriptor consist of two fields the first field
 is the length of the fixed information field.  The second is the
 length of the Record format section.  The fixed information is the
 IE's that apply to all the records that follow. The Record Format is
 the list of IE's that make up each record. The individual record
 section contains the individual records that are being reported in
 the format given by the Record Format section.
  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 = 18           |          LENGTH               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |  Length of fixed Information  |   Length of Record Format     |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 ~                     Fixed Information                         ~
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 ~                       Record Format                           ~
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 |                    Individual Record (1)                      |
 |                    Individual Record (2)                      |
 |                    Individual Record (3)                      |
 |                             .                                 |
 ~                             .                                 ~
 |                             .                                 |
 |                    Individual Record (n)                      |
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Amsden, et. al. Informational [Page 12] RFC 2124 LFAP March 1997

Flow Failure Code IE

 Flow failure code is the reason why a operation an a given flow
 failed. IE format 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 = 19           |          LENGTH = 4           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                     Flow Failure Code                         |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Flow failure code has one of the following values and meanings:
   0 - POLICY_REJECT        - A policy reject has occurred
   1 - NO_SUCH_FLOW         - The specified was flow was not found
   2 - AMBIGUOUS            - Duplicate FAR caused this error
   3 - DESTINATION_UNKNOWN  - The redirect destination was unknown

Command Code IE

 Command Code is a administrative request command to perform a
 particular function. IE format 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 = 20           |          LENGTH = 4           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                       Command  Code                           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Command code has one of the following values and meanings:
   0 - RETURN_INDICATED_FLOWS    - Return FUNs indicated
   1 - RETURN_ALL_CHANGED_FLOWS  - Return FUNs indicated
   2 - RETURN_ALL_FLOWS          - Return FUNs indicated
   3 - RETURN_FLOW_PREFIX        - Return a new flow prefix

Amsden, et. al. Informational [Page 13] RFC 2124 LFAP March 1997

Flow Identifier Prefix IE

 The flow Identifier prefix IE gives the prefix that the FAS has
 created to maintain a globally unique ID. IE format 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 = 21           |          Length = 8           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 |+-+-+-+-+-   FAS assigned Flow Identifier Prefix      -+-+-+-+-+
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

3.2. Flow Admission Request (FAR) Message

 Status is set to SUCCESS in FAR messages. In addition, FAR messages
 may contain the following IEs:
    Source Switch Address IE  - address of switch making request
    Dest Switch Address IE    - address of switch to which the
                                request is made
    Source Address IE         - flow "from" address
    Destination Address IE    - flow "to" address
    Service Identifier IE     - identifier for service requested
    Flow ID IE                - locally unique identifier for flow
                                (unique to update reporting entity)
    Client Data IE            - client data as applied to this request
    Time IE                   - switch time of admission request
 Mandatory IE's
    Source Address
    Destination Address
    Flow ID
    Time
 Optional IE's
    Source Switch Address
    Destination Switch Address
    Client Data

Amsden, et. al. Informational [Page 14] RFC 2124 LFAP March 1997

 FAR messages are sent by a switch CCE when it seeks verification of
 validity of a flow that is about to be established. FAR messages
 refer to a single flow only and do not multi IE functionality. Source
 and destination addresses are those determined by the switch CCE as
 the points of origin and termination of a flow. Service ID is the
 service type/category associated with the desired flow. The client
 data is arbitrary information about the client associated with the
 desired flow.

3.3. Flow Admission Acknowledge (FAA) Message

 Status reflects the result of the corresponding FAR message (see
 Error Handling for details). Message ID is copied from the FAR
 message. In addition, FAA messages may have the following IEs:
    Optional Operating Policy IE  - policy(s) that may apply to
                                    this flow.
    Mandatory Operating Policy IE - policy(s) that must apply to
                                    this flow.
    Destination Address IE        - may be included if the flow
                                    should be redirected.
    Flow Failure Code IE          - indicates the cause of flow
                                    failure
 FAA messages are sent by a FAS in response to FAR messages received
 from a switch CCE. Operating policy information is that determined by
 the FAS as either desirable or required for the flow specified in the
 corresponding FAR message.

3.4. Flow Admission Update (FAU) Message

 Status reflects the result of the corresponding FAA message (see
 Error Handling for details).  Message ID is copied from the FAR or
 FAA message. In addition, FAU messages may have the following IEs:
    Flow ID IE           - identifier for the flow
    Flow Failure Code IE - indicates the cause of flow failure
 FUA messages are sent by a switch CCE in response to FAA messages
 received from a FAS.  The FAU message is returned by the switch CCE
 only if an a error was detected as a result of the FAA message.

Amsden, et. al. Informational [Page 15] RFC 2124 LFAP March 1997

3.5. Flow Update Notification (FUN) Message

 Status is set to SUCCESS in FUN messages.  In addition, FUN messages
 may contain the following IEs:
    Time IE         - switch time of notification
    Flow ID IE      - identifier for the flow
    Flow State IE   - state of the flow at time of notification
    Byte Count IE   - octets sent and received for this flow
    Packet Count IE - packets sent and received for this flow
 Mandatory IE's
    Time - If multiple IE, only needs to be given once in fixed
           information section. If given in record format must be
           in each individual record.
 Optional IE's at least one must be present
    Flow State
    Byte Count
    Packet Count
 FUN messages are sent periodically (possibly as specified in an
 operating policy associated with the flow) by an CCE to the FAS. The
 Time IE may be given first and only once. If it is only a single flow
 being reported on then just the IE's and their values are returned.
 If multiple flows are to be reported on then the multiple record IE
 should be used. This results in reduced overhead on transmissions.
 FUN messages may are also be sent as a result of a AR message or a
 FCR message. The FCR message would be one that request that the flow
 state be set to inactive.
 The flow ID identifies the flow to which this update applies.  Flow
 state is the state of the flow at the time this message is sent.
 Counts are as specified in the IE definitions.  The FAS's are
 coordinated and will resolve the reception of FUN information from a
 CCE who has lost connection with its FAS and has gone to a
 alternative FAS.

3.6. Flow Update Acknowledge (FUA) Message

 Status is set to SUCCESS in FUA messages unless an error is detected
 (see "Error Handling"). Message ID is copied from the FUN message.

Amsden, et. al. Informational [Page 16] RFC 2124 LFAP March 1997

 FUA messages are sent by the FAS to acknowledge a FUN message from
 the switch CCE. If a FUN message contained a multiple record IE and
 any of the updates had a error then the FUA would contain a multiple
 IE with a Flow ID and Flow Failure Code. A status of SUCCESS
 indicates that the information in the corresponding FUN message has
 been accepted and is now the responsibility of the FAS.

3.7. Flow Change Request (FCR) Message

 Status is set to SUCCESS in FCR messages. In addition, a FCR message
 may contain the following IEs:
    Flow ID IE                    - identifier for the flow.
    Flow State IE                 - set to inactive to stop a flow.
    Optional Operating Policy IE  - possibly new policy(s) that may
                                    apply to this flow.
    Mandatory Operating Policy IE - possibly new policy(s) that must
                                    apply to this flow.
 Mandatory IE's
    Flow ID
 Optional IE's
    Flow State
    Optional Operating Policy
    Mandatory Operating Policy
 FCR messages are sent by the FAS to the CCE to provide additional (or
 change existing) operating policy information or to stop a flow.
 Flow ID is used to identify the flow to which this message applies.
 The FAS can stop a flow by setting it's flow state to inactive.  This
 will cause the CCE to generate a FUN message with the final flow
 statistics.  It will also cause the CCE to return a inactive flow
 state on the given flow.  If the FAS wishes to change operating
 policy information it merely includes the new information in the FCR
 message along with the flow id.

3.8. Flow Change Acknowledge (FCA) Message

 Status is set to SUCCESS in FCA messages unless an error is detected
 (see "Error Handling").  Message ID is copied from the FCR message.
 FCA messages contain IEs if a error was detected in the corresponding
 FCR message (see "Error Handling").
 If an error occurs then a FCR may contain the following IE's
    Flow ID IE        - if FAS requested statistics on an
                        unknown flow.

Amsden, et. al. Informational [Page 17] RFC 2124 LFAP March 1997

    Flow Failure Code - for the Flow ID IE above.
 FCA messages are sent by a switch CCE in response to an FCR.

3.9. Administrative Request (AR) Message

 Status is set to SUCCESS in AR messages. In addition, AR messages may
 contain the Command IEs:
 Mandatory IE's
    Command IE
 AR messages are sent by either the a switch CCE or the FAS when they
 seeks to perform one of the Command IE's.

3.10. Administrative Request Acknowledge (ARA) Message

 Status reflects the result of the corresponding AR message (see Error
 Handling for details). Message ID is copied from the AR message. In
 addition, ARA messages may have the following IEs:
    Flow ID IE                 - if FAS requested statistics on an
                                 unknown flow.
    Flow Failure Code          - for the Flow ID IE above.
    Flow Identifier Prefix IE  - if the ARA is the response to a CCE
                                 Command to RETURN_FLOW_PREFIX.
 ARA messages are sent by a FAS or CCE in response to AR message
 received CCE or FAS respectively.

4. Error Handling

 Incompatible version - Receipt of any LFAP request or notification
 message, with a version number other than that (or those) supported
 by the receiving component will result in a response (acknowledge)
 message with a Status of VERSION. The resulting message will contain
 no IEs and, as a result, may be considered a generic FAILURE message.
 Corrupted message contents - Receipt of a LFAP message which cannot
 be understood will result in a similar generic FAILURE message with
 Status set to CORRUPTED. A FAA message may contain a Flow ID IE only
 if this IE is included in the portion of the corrupt LFAP message
 that is before the point where corruption occurs. The LFAP sender
 should re-send the original message at least one time if it is still
 desired to admit the requested connection.

Amsden, et. al. Informational [Page 18] RFC 2124 LFAP March 1997

 With the exception of incompatible version and corrupted message
 contents, error handling is naturally related to the processing of
 response messages by both response sender and receiver. Below
 sections are thus organized around processing of FAA, FUA, FCA and
 ARA messages.

4.1. FAA Related Error Handling

 Non-unique Flow ID - Receipt of a FAR message with a non-unique Flow
 ID may occur for two reasons: the CCE may have re-sent a FAR message
 and an error may have occurred in the ID generation function.  If the
 entire message is the same in every respect, with the possible
 exception of Message ID, as a FAR message received previously, the
 FAS will respond in the same way as it would have responded to that
 prior message.  Otherwise, the Flow ID will be returned with a Flow
 Failure Code set to AMBIGUOUS. The CCE should choose a new Flow ID
 and retry the FAR message if it is still desired to admit the
 requested connection.
 Flow is inadmissible - The FAS may determine that flow is not
 admissible for policy reasons. In this case the Flow ID is returned
 along with the Flow Failure Code of POLICY_REJECT.

4.2. FUA Related Error Handling

 Flow Not Admitted - Receipt of Flow information for an unadmitted
 connection. Flow ID IE identifies a flow which was not admitted or
 for which admission status has been lost. The FAS will return the
 Flow ID and a Flow Failure Code of NO_SUCH_FLOW. The switch CCE
 should send an appropriate FAR message. The FAS may track occurrences
 of this error and send a FCR message to the CCE requesting dropping
 of the reported connection.

4.3. FCA Related Error Handling

 Flow change requested for a non-existent flow - The Flow ID IE
 identifies a connection for which this CCE has no state information.
 The FCA message has the Flow ID and a Flow Failure Code set to
 NO_SUCH_FLOW and contains the Flow ID and copied from the
 corresponding FCR message.
 Policy changes requested were not supported by the CCE.  The FCA
 message has the Flow ID and a Flow Failure Code set to POLICY_REJECT
 and contains the Flow ID copied from the corresponding FCR message.

Amsden, et. al. Informational [Page 19] RFC 2124 LFAP March 1997

4.4. ARA Related Error Handling

 Flow statistics requested for a non-existent flow - The Flow ID IE
 identified a connection for which this CCE has no state information.
 The ARA message has the Flow ID and a Flow Failure Code set to
 NO_SUCH_FLOW and contains the Flow ID copied from the corresponding
 FCR message.  If there were multiple flows that were non-existent
 then the multi ie format could have the Flow Failure Code in the
 fixed information section and the individual Flow ID's in the record
 section.

5. Security Considerations

 Security issues are not discussed in this memo.

6. Author's Addresses

  Paul Amsden
  Phone:  +1 (603) 337-7408
  EMail:  amsden@ctron.com
  Jim Amweg
  Phone:  +1 (603) 337-5247
  EMail:  amsden@ctron.com
  Paul Calato
  Phone:  +1 (603) 337-7625
  EMail:  amsden@ctron.com
  Stephen Bensley
  Phone:  +1 (603) 337-7061
  EMail:  amsden@ctron.com
  Gregory Lyons
  Phone:  +1 (603) 337-5318
  EMail:  amsden@ctron.com

Cabletron Systems, Inc. is located at:

  P.O. Box 5005
  Rochester, NH, 03866-5005
  USA

Amsden, et. al. Informational [Page 20] RFC 2124 LFAP March 1997

7. References

 [363]   "B-ISDN ATM Adaptation Layer (AAL) Specification,"
         International Telecommunication Union, ITU-T Recommendation
         I.363, Mar. 1993.
 [1443]  "Textual Conventions for version 2 of the Simple Network
         Management Protocol (SNMPv2)", RFC 1443, April 1993.
 [1700]  Reynolds, J., and J. Postel, "Assigned Numbers", STD 2,
         RFC 1700, October 1994.
 [8824]  Information technology - Open Systems Interconnection -
         "Specification of Abstract Syntax Notation One (ASN.1),
         Second edition", ISO/IEC TR 8824: 1990 (E) 1990-12-15.
 [9577]  "Telecommunications and Information Exchange Between Systems
         - Protocol Identification in the Network Layer", ISO/IEC TR
         9577: 1990 (E) 1990-10-15.
 [LANE]  "LAN Emulation Over ATM Specification - Version 1.0", ATM
         Forum af-lane-021.000, January, 1995.

Amsden, et. al. Informational [Page 21]

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