Notification Message support for BGP Graceful Restart
draft-ietf-idr-bgp-gr-notification-04

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Last updated 2015-04-27
Replaces draft-keyupate-idr-bgp-gr-notification
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Network Working Group                                           K. Patel
Internet-Draft                                               R. Fernando
Intended status: Standards Track                           Cisco Systems
Expires: October 29, 2015                                     J. Scudder
                                                                 J. Haas
                                                        Juniper Networks
                                                          April 27, 2015

         Notification Message support for BGP Graceful Restart
               draft-ietf-idr-bgp-gr-notification-04.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

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   provisions of BCP 78 and BCP 79.

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   This document is subject to BCP 78 and the IETF Trust's Legal
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   (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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Table of Contents

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

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.

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   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 Restart flags field and the Flags field for Address
   Family are augmented as follows:

            +--------------------------------------------------+
            | 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)                |
            +--------------------------------------------------+

    Restart Flags:

            This field contains bit flags relating to restart.

                0 1 2 3
               +-+-+-+-+
               |R|N|   |
               +-+-+-+-+

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   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).

    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 usage of second most significant bit "N" is deprecated.  This bit
   SHOULD be reserved and set to 0.

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.

3.1.  Sending a Hard Reset

   A Hard Reset NOTIFICATION Message is used to indicate to a peer with
   which the Graceful Notification flag has been exchanged, that the
   session is to be fully terminated.

   When sending a Hard Reset NOTIFICATION, the data portion of the
   NOTIFICATION message MUST be used to indicate the reason for the hard
   reset.  The reason is encoded using a standard BGP Cease error
   subcode and MAY also include any relevant data subsequent to the
   subcode.

3.2.  Sending a Hard Reset

   Whenever a BGP speaker receives a NOTIFICATION message with the Cease
   Error code and Hard Reset Error subcode, the speaker MUST terminate
   the BGP session following the standard procedures in [RFC4271].

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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.

   A BGP speaker MAY continue to operate in the Graceful Restart mode
   even if it receives a Graceful Restart capability without a Graceful
   Notification Flag.

   When a BGP speaker resets its session due to a HOLDTIME expiry, it
   SHOULD follow the standard rules of the receiving speaker mentioned
   in [RFC4724] aside from generating a BGP NOTIFICATION message as
   mentioned in [RFC4271].

   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, any 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.

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7.  Security Considerations

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

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

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

   Email: rex@cisco.com

   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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