[Docs] [txt|pdf|xml|html] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: (draft-keyupate-idr-bgp-gr-notification) 00 01 02 03 04 05 06 07 08 09 10 11 12 13

Internet Engineering Task Force                                 K. Patel
Internet-Draft                                                    Arrcus
Updates: 4724 (if approved)                                  R. Fernando
Intended status: Standards Track                           Cisco Systems
Expires: December 17, 2017                                    J. Scudder
                                                                 J. Haas
                                                        Juniper Networks
                                                           June 15, 2017


         Notification Message support for BGP Graceful Restart
               draft-ietf-idr-bgp-gr-notification-13.txt

Abstract

   The BGP Graceful Restart mechanism defined in RFC 4724 limits the
   usage of BGP Graceful Restart to BGP protocol messages other than a
   BGP NOTIFICATION message.  This document updates RFC 4724 by defining
   an extension that permits the Graceful Restart procedures to be
   performed when the BGP speaker receives a BGP NOTIFICATION Message or
   the Hold Time expires.  This document also defines a new BGP
   NOTIFICATION Cease Error subcode whose effect is to request a full
   session restart instead of 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
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on December 17, 2017.

Copyright Notice

   Copyright (c) 2017 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



Patel, et al.           Expires December 17, 2017               [Page 1]


Internet-Draft       Notification support for BGP GR           June 2017


   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

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.  Receiving a Hard Reset  . . . . . . . . . . . . . . . . .   4
   4.  Operation . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  Rules for the Receiving Speaker . . . . . . . . . . . . .   5
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   8.  Normative 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 or the Hold Time expires.  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.

   At a high level, this document can be summed up as follows.  When a
   BGP session is reset, both speakers operate as "Receiving Speakers"
   according to [RFC4724], meaning they retain each other's routes.
   This is also true for HOLDTIME expiration.  The functionality can be
   defeated using a "Hard Reset" subcode for the BGP NOTIFICATION Cease
   Error code.  If a Hard Reset is used, a full session reset is
   performed.






Patel, et al.           Expires December 17, 2017               [Page 2]


Internet-Draft       Notification support for BGP GR           June 2017


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.  The Restart
   flags field is 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|   |
               +-+-+-+-+

   The most significant ("Restart State", or "R") bit is defined in
   [RFC4724].

   The second most significant bit ("N") is defined as the BGP Graceful
   Notification bit, which is used to indicate Graceful Restart support
   for BGP NOTIFICATION messages.  A BGP speaker indicates support for



Patel, et al.           Expires December 17, 2017               [Page 3]


Internet-Draft       Notification support for BGP GR           June 2017


   the procedures of this document, by advertising a Graceful Restart
   Capability with its Graceful NOTIFICATION bit set (value 1).  This
   also implies support for the format for a BGP NOTIFICATION Cease
   message defined in [RFC4486].

3.  BGP Hard Reset Subcode

   A new BGP NOTIFICATION Cease message subcode is defined known as the
   BGP Hard Reset Subcode.  The value of this subcode is discussed in
   Section 6.  We refer to a BGP NOTIFICATION Cease message with the
   Hard Reset subcode as a Hard Reset message, or just a Hard Reset.

3.1.  Sending a Hard Reset

   A Hard Reset 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, the data portion of the NOTIFICATION is
   encoded as follows:

       +--------+--------+--------
       | ErrCode| Subcode| Data
       +--------+--------+--------

   ErrCode is a BGP Error Code (as documented in the IANA BGP Error
   Codes registry) that indicates the reason for the hard reset.
   Subcode is a BGP Error Subcode (as documented in the IANA BGP Error
   Subcodes registry) as appropriate for the ErrCode.  Similarly, Data
   is as appropriate for the ErrCode and Subcode.

3.2.  Receiving a Hard Reset

   Whenever a BGP speaker receives a Hard Reset, 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 MUST advertise the BGP Graceful
   Notification "N" bit using the Graceful Restart Capability as defined
   in [RFC4724].

   When such a BGP speaker has received the "N" bit from its peer, and
   receives from that peer a BGP NOTIFICATION message other than a Hard
   Reset, it MUST follow the rules for the Receiving Speaker mentioned




Patel, et al.           Expires December 17, 2017               [Page 4]


Internet-Draft       Notification support for BGP GR           June 2017


   in Section 4.1.  The BGP speaker generating the BGP NOTIFICATION
   message MUST also follow the rules for the Receiving Speaker.

   When a BGP speaker resets its session due to a HOLDTIME expiry, it
   should generate the relevant BGP NOTIFICATION message as mentioned in
   [RFC4271], but subsequently it MUST follow the rules for the
   Receiving Speaker mentioned in Section 4.1.

   A BGP speaker SHOULD NOT send a Hard Reset to a peer from which it
   has not received the "N" bit.  We note, however, that if it did so
   the effect would be as desired in any case, since according to
   [RFC4271] and [RFC4724] any NOTIFICATION message, whether recognized
   or not, results in a session reset.  Thus the only negative effect to
   be expected from sending the Hard Reset to a peer that hasn't
   advertised compliance to this specification would be that the peer
   would be unable to properly log the associated information.

   Once the session is re-established, both BGP speakers SHOULD set
   their "Forwarding State" bit to 1.  If the "Forwarding State" bit is
   not set, then according to the procedures of [RFC4724] section 4.2,
   the relevant routes will be flushed, defeating the goals of this
   specification.

4.1.  Rules for the Receiving Speaker

   [RFC4724] section 4.2 defines rules for the Receiving Speaker.  These
   are modified as follows.

   As part of this extension, routes from the peer previously marked as
   stale MUST NOT be deleted, until and unless the optional timer
   mentioned in the final paragraph of [RFC4724] section 4.2 expires, or
   unless a Hard Reset is performed.  This supersedes the "consecutive
   restarts" requirement in the third paragraph of [RFC4724] section
   4.2.

   In addition to the rules already specified in [RFC4724] section 4.2
   for how variations in the received Graceful Restart Capability should
   be interpreted (the paragraph that begins "Once the session is re-
   established..."), if the Graceful Notification ("N") bit is not set
   in the newly received Graceful Restart Capability, no new actions are
   triggered on the Receiving Speaker -- in particular, a clear "N" bit
   does not trigger deletion of stale routes.

   Other than these modifications, the rules for the Receiving Speaker
   are as specified in [RFC4724] section 4.2.






Patel, et al.           Expires December 17, 2017               [Page 5]


Internet-Draft       Notification support for BGP GR           June 2017


5.  Acknowledgements

   The authors would like to thank Jim Uttaro for the suggestion, and
   Emmanuel Baccelli, Bruno Decraene, Chris Hall, Paul Mattes and Robert
   Raszuk for their review and comments.

6.  IANA Considerations

   IANA has temporarily assigned subcode 9, named "Hard Reset", in the
   "BGP Cease NOTIFICATION message subcodes" registry.  Upon publication
   of this document as an RFC, IANA is requested to make this allocation
   permanent.

7.  Security Considerations

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

8.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,
              <http://www.rfc-editor.org/info/rfc4271>.

   [RFC4486]  Chen, E. and V. Gillet, "Subcodes for BGP Cease
              Notification Message", RFC 4486, DOI 10.17487/RFC4486,
              April 2006, <http://www.rfc-editor.org/info/rfc4486>.

   [RFC4724]  Sangli, S., Chen, E., Fernando, R., Scudder, J., and Y.
              Rekhter, "Graceful Restart Mechanism for BGP", RFC 4724,
              DOI 10.17487/RFC4724, January 2007,
              <http://www.rfc-editor.org/info/rfc4724>.

Authors' Addresses

   Keyur Patel
   Arrcus

   Email: keyur@arrcus.com






Patel, et al.           Expires December 17, 2017               [Page 6]


Internet-Draft       Notification support for BGP GR           June 2017


   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


























Patel, et al.           Expires December 17, 2017               [Page 7]


Html markup produced by rfcmarkup 1.123, available from https://tools.ietf.org/tools/rfcmarkup/