Network Working Group                                            E. Chen
Request for Comments: 4486                                 Cisco Systems
Category: Standards Track                                      V. Gillet
                                                         France Telecom
                                                             April 2006


             Subcodes for BGP Cease Notification Message

Status of This Memo

  This document specifies an Internet standards track protocol for the
  Internet community, and requests discussion and suggestions for
  improvements.  Please refer to the current edition of the "Internet
  Official Protocol Standards" (STD 1) for the standardization state
  and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

  Copyright (C) The Internet Society (2006).

Abstract

  This document defines several subcodes for the BGP Cease NOTIFICATION
  message that would provide more information to aid network operators
  in correlating network events and diagnosing BGP peering issues.

1.  Introduction

  This document defines several subcodes for the BGP Cease NOTIFICATION
  message that would provide more information to aid network operators
  in correlating network events and diagnosing BGP peering issues.  It
  also recommends that a BGP speaker implement a backoff mechanism in
  re-trying a BGP connection after the speaker receives a NOTIFICATION
  message with certain CEASE subcode.

2.  Specification of Requirements

  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 [RFC-2119].










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3.  Subcode Definition

  The following subcodes are defined for the Cease NOTIFICATION
  message:

     Subcode     Symbolic Name

        1        Maximum Number of Prefixes Reached
        2        Administrative Shutdown
        3        Peer De-configured
        4        Administrative Reset
        5        Connection Rejected
        6        Other Configuration Change
        7        Connection Collision Resolution
        8        Out of Resources

4.  Subcode Usage

  If a BGP speaker decides to terminate its peering with a neighbor
  because the number of address prefixes received from the neighbor
  exceeds a locally configured upper bound (as described in [BGP-4]),
  then the speaker MUST send to the neighbor a NOTIFICATION message
  with the Error Code Cease and the Error Subcode "Maximum Number of
  Prefixes Reached".  The message MAY optionally include the Address
  Family information [BGP-MP] and the upper bound in the "Data" field,
  as shown in Figure 1, where the meaning and use of the <AFI, SAFI>
  tuple is the same as defined in [BGP-MP], Section 7.

                 +-------------------------------+
                 | AFI (2 octets)                |
                 +-------------------------------+
                 | SAFI (1 octet)                |
                 +-------------------------------+
                 | Prefix upper bound (4 octets) |
                 +-------------------------------+

                    Figure 1: Optional Data Field

  If a BGP speaker decides to administratively shut down its peering
  with a neighbor, then the speaker SHOULD send a NOTIFICATION message
  with the Error Code Cease and the Error Subcode "Administrative
  Shutdown".

  If a BGP speaker decides to de-configure a peer, then the speaker
  SHOULD send a NOTIFICATION message with the Error Code Cease and the
  Error Subcode "Peer De-configured".





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  If a BGP speaker decides to administratively reset the peering with a
  neighbor, then the speaker SHOULD send a NOTIFICATION message with
  the Error Code Cease and the Error Subcode "Administrative Reset".

  If a BGP speaker decides to disallow a BGP connection (e.g., the peer
  is not configured locally) after the speaker accepts a transport
  protocol connection, then the BGP speaker SHOULD send a NOTIFICATION
  message with the Error Code Cease and the Error Subcode "Connection
  Rejected".

  If a BGP speaker decides to administratively reset the peering with a
  neighbor due to a configuration change other than the ones described
  above, then the speaker SHOULD send a NOTIFICATION message with the
  Error Code Cease and the Error Subcode "Other Configuration Change".

  If a BGP speaker decides to send a NOTIFICATION message with the
  Error Code Cease as a result of the collision resolution procedure
  (as described in [BGP-4]), then the subcode SHOULD be set to
  "Connection Collision Resolution".

  If a BGP speaker runs out of resources (e.g., memory) and decides to
  reset a session, then the speaker MAY send a NOTIFICATION message
  with the Error Code Cease and the Error Subcode "Out of Resources".

  It is RECOMMENDED that a BGP speaker behave as though the
  DampPeerOscillations attribute [BGP-4] were true for this peer when
  re-trying a BGP connection after the speaker receives a Cease
  NOTIFICATION message with a subcode of "Administrative Shutdown",
  "Peer De-configured", "Connection Rejected", or "Out of Resources".
  An implementation SHOULD impose an upper bound on the number of
  consecutive automatic retries.  Once this bound is reached, the
  implementation would stop re-trying any BGP connections until some
  administrative intervention, i.e., set the AllowAutomaticStart
  attribute [BGP-4] to FALSE.

5.  IANA Considerations

  This document defines the subcodes 1 - 8 for the BGP Cease
  NOTIFICATION message.  Future assignments are to be made using either
  the Standards Action process defined in [RFC-2434], or the Early IANA
  Allocation process defined in [RFC-4020].  Assignments consist of a
  name and the value.

6.  Security Considerations

  This extension to BGP does not change the underlying security issues
  inherent in the existing BGP.




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7.  Acknowledgements

  The authors would like to thank Yakov Rekhter, Pedro Marques, Andrew
  Lange, and Don Goodspeed for their review and suggestions.

8.  References

8.1.  Normative References

  [BGP-4]    Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
             Protocol 4 (BGP-4)", RFC 4271, January 2006.

  [BGP-MP]   Bates, T., Rekhter, Y., Chandra, R., and D. Katz,
             "Multiprotocol Extensions for BGP-4", RFC 2858, June 2000.

  [RFC-2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
             IANA Considerations Section in RFCs", BCP 26, RFC 2434,
             October 1998.

  [RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, March 1997.

8.2.  Informative References

  [RFC-4020] Kompella, K. and A. Zinin, "Early IANA Allocation of
             Standards Track Code Points", BCP 100, RFC 4020, February
             2005.
























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Authors' Addresses

  Enke Chen
  Cisco Systems, Inc.
  170 W. Tasman Dr.
  San Jose, CA 95134
  USA

  EMail: [email protected]


  Vincent Gillet
  France Telecom Longues Distances
  61, rue des Archives
  75003 Paris FRANCE

  EMail: [email protected]


































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