Subcodes for BGP Cease Notification Message
RFC 4486

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].

Chen & Gillet               Standards Track                     [Page 1]
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".

Chen & Gillet               Standards Track                     [Page 2]
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