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Versions: 00 draft-ietf-idr-bgp-gr-notification

Network Working Group                                           K. Patel
Internet-Draft                                               R. Fernando
Intended status: Standards Track                           Cisco Systems
Expires: January 3, 2012                                      J. Scudder
                                                                 J. Haas
                                                        Juniper Networks
                                                            July 2, 2011


         Notification Message support for BGP Graceful Restart
             draft-keyupate-idr-bgp-gr-notification-00.txt

Abstract

   The current BGP Graceful Restart mechanism limits the usage of BGP
   Graceful Restart to BGP protocol messages other than a BGP
   NOTIFICATION message.  This document defines an extension to the BGP
   Graceful Restart that permits the Graceful Restart procedures to be
   performed when the BGP speaker receives a BGP NOTIFICATION Message.
   This document also defines a new BGP NOTIFICATION Cease Error subcode
   to prevent BGP speakers supporting the extension defined in this
   document from performing a Graceful Restart.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
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   This Internet-Draft will expire on January 3, 2012.

Copyright Notice

   Copyright (c) 2011 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



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   publication of this document.  Please review these documents
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   include Simplified BSD License text as described in Section 4.e of
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   This document may contain material from IETF Documents or IETF
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   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

































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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 4
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . . . 4
   2.  Modifications to BGP Graceful Restart Capability  . . . . . . . 4
   3.  BGP Hard Reset Subcode  . . . . . . . . . . . . . . . . . . . . 5
   4.  Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 7
     8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 7
     8.2.  Informative References  . . . . . . . . . . . . . . . . . . 7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 7





































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1.  Introduction

   For many classes of errors, the BGP protocol must send a NOTIFICATION
   message and reset the peering session to handle the error condition.
   The BGP Graceful Restart extension defined in [RFC4724] requires that
   normal BGP procedures defined in [RFC4271] be followed when a
   NOTIFICATION message is sent or received.  This document defines an
   extension to BGP Graceful Restart that permits the Graceful Restart
   procedures to be performed when the BGP speaker receives a
   NOTIFICATION message.  This permits the BGP speaker to avoid flapping
   reachability and continue forwarding while the BGP speaker restarts
   the session to handle errors detected in the BGP protocol.

   This document defines a BGP NOTIFICATION cease Error subcode for the
   Cease Error code to prevent BGP speakers supporting the extension
   defined in this document from performing a Graceful Restart.

1.1.  Requirements Language

   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].


2.  Modifications to BGP Graceful Restart Capability

   The BGP Graceful Restart Capability is augmented to signal the
   Graceful Restart support for BGP NOTIFICATION messages.  In
   particular, the flags field for Address Family is augmented as
   follows:





















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            +--------------------------------------------------+
            | Restart Flags (4 bits)                           |
            +--------------------------------------------------+
            | Restart Time in seconds (12 bits)                |
            +--------------------------------------------------+
            | Address Family Identifier (16 bits)              |
            +--------------------------------------------------+
            | Subsequent Address Family Identifier (8 bits)    |
            +--------------------------------------------------+
            | Flags for Address Family (8 bits)                |
            +--------------------------------------------------+
            | ...                                              |
            +--------------------------------------------------+
            | Address Family Identifier (16 bits)              |
            +--------------------------------------------------+
            | Subsequent Address Family Identifier (8 bits)    |
            +--------------------------------------------------+
            | Flags for Address Family (8 bits)                |
            +--------------------------------------------------+



    Flags for Address Family:

            This field contains bit flags relating to routes that were
            advertised with the given AFI and SAFI.


                0 1 2 3 4 5 6 7
               +-+-+-+-+-+-+-+-+
               |F|N| Reserved  |
               +-+-+-+-+-+-+-+-+

   The second most significant bit "N" is defined as a BGP Graceful
   Notification bit, which is used to indicate the Graceful Restart
   support for BGP NOTIFICATION messages.  BGP speaker indicates the
   Graceful Restart support for BGP NOTIFICATION messages and its
   ability to handle the new BGP NOTIFICATION Cease message subcode and
   the format for a BGP NOTIFICATION Cease message defined in [RFC4486]
   when the Graceful NOTIFICATION bit is set (value 1).


3.  BGP Hard Reset Subcode

   A new BGP Cease message subcode is defined known as BGP Hard Reset
   Subcode.  The value of this subcode is 9.

   Whenever a BGP speaker receives a NOTIFICATION message with the Cease



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   Error code and Hard Reset Error subcode, the speaker MUST terminate
   the BGP session following the standard procedures in [RFC4271].


4.  Operation

   A BGP speaker that is willing to receive and send BGP NOTIFICATION
   messages in Graceful mode should advertise the BGP Graceful
   Notification Flag "N" using the Graceful Restart Capability as
   defined in [RFC4724].

   When a BGP Speaker receives a BGP NOTIFICATION message, it SHOULD
   follow the standard rules of the receiving speaker mentioned in
   [RFC4724] for all AFI/SAFIs for which it has announced the BGP
   Graceful Notification flag.  The BGP speaker generating a BGP
   NOTIFICATION message SHOULD follow the standard rules of the
   receiving Speaker in [RFC4724] for all AFI/SAFIs that were announced
   with the BGP Graceful Notification flag.

   Once the session is re-established, both BGP speakers MUST set their
   "Forwarding State" bit to 1 if they want to apply planned graceful
   restart.  The handling of the "Forwarding State" bit should be done
   as specified by the procedures of the Receiving speaker in [RFC4724]
   are applied.

   As part of this extension, possible consecutive restarts SHOULD NOT
   delete a route (from the peer) previously marked as stale, until
   required by rules mentioned in [RFC4724].


5.  Acknowledgements

   The authors would like to thank Robert Raszuk for the review and
   comments.


6.  IANA Considerations

   This document defines a new BGP Cease message subcode known as BGP
   Hard Reset Subcode.  IANA mantains the list of existing BGP Cease
   message subcodes.  This document proposes defining a new BGP Cease
   message subcode known as BGP Hard Reset Subcode with the value 9.


7.  Security Considerations

   This extension to BGP does not change the underlying security issues
   inherent in the existing [RFC4724] and [RFC4271]



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8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2842]  Chandra, R. and J. Scudder, "Capabilities Advertisement
              with BGP-4", RFC 2842, May 2000.

   [RFC3392]  Chandra, R. and J. Scudder, "Capabilities Advertisement
              with BGP-4", RFC 3392, November 2002.

   [RFC4271]  Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
              Protocol 4 (BGP-4)", RFC 4271, January 2006.

   [RFC4486]  Chen, E. and V. Gillet, "Subcodes for BGP Cease
              Notification Message", RFC 4486, April 2006.

   [RFC4724]  Sangli, S., Chen, E., Fernando, R., Scudder, J., and Y.
              Rekhter, "Graceful Restart Mechanism for BGP", RFC 4724,
              January 2007.

8.2.  Informative References

   [RFC2858]  Bates, T., Rekhter, Y., Chandra, R., and D. Katz,
              "Multiprotocol Extensions for BGP-4", RFC 2858, June 2000.


Authors' Addresses

   Keyur Patel
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA  95134
   USA

   Email: keyupate@cisco.com


   Rex Fernando
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA  95134
   USA

   Email: rex@cisco.com




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   John Scudder
   Juniper Networks
   1194 N. Mathilda Ave
   Sunnyvale, CA  94089
   USA

   Email: jgs@juniper.net


   Jeff Haas
   Juniper Networks
   1194 N. Mathilda Ave
   Sunnyvale, CA  94089
   USA

   Email: jhaas@juniper.net



































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