





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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RFC 4486        BGP Cease Notification Message Subcodes       April 2006


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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RFC 4486        BGP Cease Notification Message Subcodes       April 2006


   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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RFC 4486        BGP Cease Notification Message Subcodes       April 2006


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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RFC 4486        BGP Cease Notification Message Subcodes       April 2006


Authors' Addresses

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

   EMail: enkechen@cisco.com


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

   EMail: vgi@opentransit.net


































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RFC 4486        BGP Cease Notification Message Subcodes       April 2006


Full Copyright Statement

   Copyright (C) The Internet Society (2006).

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