





Internet Engineering Task Force (IETF)                          K. Patel
Request for Comments: 7313                                       E. Chen
Updates: 2918                                              Cisco Systems
Category: Standards Track                           B. Venkatachalapathy
ISSN: 2070-1721                                                July 2014


              Enhanced Route Refresh Capability for BGP-4

Abstract

   In this document, we enhance the existing BGP route refresh
   mechanisms to provide for the demarcation of the beginning and the
   ending of a route refresh.  The enhancement can be used to facilitate
   correction of BGP Routing Information Base (RIB) inconsistencies in a
   non-disruptive manner.  This document updates RFC 2918.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7313.

Copyright Notice

   Copyright (c) 2014 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
   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.






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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   2
   3.  Protocol Extensions . . . . . . . . . . . . . . . . . . . . .   2
     3.1.  Enhanced Route Refresh Capability . . . . . . . . . . . .   3
     3.2.  Subtypes for ROUTE-REFRESH Message  . . . . . . . . . . .   3
   4.  Operation . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   5.  Error Handling  . . . . . . . . . . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   9.  Normative References  . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   It is sometimes necessary to perform routing consistency validations
   such as checking for possible missing route withdrawals between BGP
   speakers [RFC4271].  Currently, such validations typically involve
   offline, manual operations that can be tedious and time-consuming.

   In this document, we enhance the existing BGP route refresh
   mechanisms [RFC2918] to provide for the demarcation of the beginning
   and the ending of a route refresh (which refers to the complete
   re-advertisement of the Adj-RIB-Out to a peer, subject to routing
   policies).  The enhancement can be used to facilitate online, non-
   disruptive consistency validation of BGP routing updates.

   This document updates [RFC2918] by redefining a field in the ROUTE-
   REFRESH message that was previously designated as Reserved.

2.  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 [RFC2119] only when
   they appear in all upper case.  They may also appear in lower or
   mixed case as English words, without any normative meaning.

3.  Protocol Extensions

   The BGP protocol extensions introduced in this document include the
   definition of a new BGP capability, named "Enhanced Route Refresh
   Capability", and the specification of the message subtypes for the
   ROUTE-REFRESH message.






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3.1.  Enhanced Route Refresh Capability

   The "Enhanced Route Refresh Capability" is a new BGP capability
   [RFC5492].  IANA has assigned a Capability Code of 70 for this
   capability.  The Capability Length field of this capability is zero.

   By advertising this capability to a peer, a BGP speaker conveys to
   the peer that the speaker supports the message subtypes for the
   ROUTE-REFRESH message and the related procedures described in this
   document.

3.2.  Subtypes for ROUTE-REFRESH Message

   The "Reserved" field of the ROUTE-REFRESH message specified in
   [RFC2918] is redefined as the "Message Subtype" with the following
   values:

             0 - Normal route refresh request [RFC2918]
                 with/without Outbound Route Filtering (ORF) [RFC5291]
             1 - Demarcation of the beginning of a route refresh
                 (BoRR) operation
             2 - Demarcation of the ending of a route refresh
                 (EoRR) operation
           255 - Reserved

   The remaining values of the message subtypes are reserved for future
   use; see Section 6 ("IANA Considerations").  The use of the new
   message subtypes is described in Section 4 ("Operation").

4.  Operation

   A BGP speaker that supports the message subtypes for the ROUTE-
   REFRESH message and the related procedures SHOULD advertise the
   "Enhanced Route Refresh Capability".

   The following procedures are applicable only if a BGP speaker has
   received the "Enhanced Route Refresh Capability" from a peer.

   Before the speaker starts a route refresh that is either initiated
   locally, or in response to a "normal route refresh request" from the
   peer, the speaker MUST send a BoRR message.  After the speaker
   completes the re-advertisement of the entire Adj-RIB-Out to the peer,
   it MUST send an EoRR message.

   Conceptually, the "entire Adj-RIB-Out" for a peer in this section
   refers to all the route entries in the "Adj-RIB-Out" for the peer at
   the start of the route refresh operation.  These route entries
   comprise both the reachability as well as unreachability information.



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   When a route entry in the "Adj-RIB-Out" changes, only the modified
   route entry needs to be advertised.

   In processing a ROUTE-REFRESH message from a peer, the BGP speaker
   MUST examine the "message subtype" field of the message and take the
   appropriate actions.  The message processing rules for ROUTE-REFRESH
   message with subtype of 0 are described in [RFC2918] and [RFC5291].
   A BGP speaker can receive a BoRR message from a peer at any time,
   either as a result of a peer responding to a ROUTE-REFRESH message,
   or as a result of a peer unilaterally initiating a route refresh.
   When a BGP speaker receives a BoRR message from a peer, it MUST mark
   all the routes with the given Address Family Identifier and
   Subsequent Address Family Identifier, <AFI, SAFI> [RFC2918], from
   that peer as stale.  As it receives routes from its peer's subsequent
   Adj-RIB-Out re-advertisement, these replace any corresponding stale
   routes.  When a BGP speaker receives an EoRR message from a peer, it
   MUST immediately remove any routes from the peer that are still
   marked as stale for that <AFI, SAFI>.  Such purged routes MAY be
   logged for future analysis.  A BGP speaker MAY ignore any EoRR
   message received without a prior receipt of an associated BoRR
   message.  Such messages MAY be logged for future analysis.

   An implementation MAY impose a locally configurable upper bound on
   how long it would retain any stale routes.  Once the upper bound is
   reached, the implementation MAY remove any routes from the peer that
   are still marked as stale for that <AFI, SAFI> without waiting for an
   EoRR message.

   The following procedures are specified in order to simplify the
   interaction with the BGP Graceful Restart [RFC4724].  In particular,
   these procedures ensure that End-of-RIB (EoR) defined in Graceful
   Restart and EoRR as defined in this specification are kept separate,
   thereby avoiding any premature cleanup of stale routes.  For a BGP
   speaker that supports the BGP Graceful Restart, it MUST NOT send a
   BoRR for an <AFI, SAFI> to a neighbor before it sends the EoR for the
   <AFI, SAFI> to the neighbor.  A BGP speaker that has received the
   Graceful Restart Capability from its neighbor MUST ignore any BoRRs
   for an <AFI, SAFI> from the neighbor before the speaker receives the
   EoR for the given <AFI, SAFI> from the neighbor.  The BGP speaker
   SHOULD log an error of the condition for further analysis.











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5.  Error Handling

   This document defines a new NOTIFICATION error code:

          Error Code   Name

              7        ROUTE-REFRESH Message Error

   The following error subcode is defined as well:

          Subcode      Name

             1         Invalid Message Length

   The error handling specified in this section is applicable only when
   a BGP speaker has received the "Enhanced Route Refresh Capability"
   from a peer.

   If the length, excluding the fixed-size message header, of the
   received ROUTE-REFRESH message with Message Subtype 1 and 2 is not 4,
   then the BGP speaker MUST send a NOTIFICATION message with the Error
   Code of "ROUTE-REFRESH Message Error" and the subcode of "Invalid
   Message Length".  The Data field of the NOTIFICATION message MUST
   contain the complete ROUTE-REFRESH message.

   When the BGP speaker receives a ROUTE-REFRESH message with a "Message
   Subtype" field other than 0, 1, or 2, it MUST ignore the received
   ROUTE-REFRESH message.  It SHOULD log an error for further analysis.























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6.  IANA Considerations

   This document defines the Enhanced Route Refresh Capability for BGP.
   In the "Capability Codes" registry, IANA has assigned it value 70,
   referencing this document.

   This document also defines two new subcodes for the Route Refresh
   message.  They have been registered with the IANA in a new registry
   as follows:

           Under "Border Gateway Protocol (BGP) Parameters":
           Registry: "BGP Route Refresh Subcodes"
           Reference: [RFC7313]
           Registration Procedure(s): Values 0-127 Standards Action,
             values 128-254 First Come First Served

           Value   Code                Reference
           0       Route-Refresh       [RFC2918], [RFC5291]
           1       BoRR                [RFC7313]
           2       EoRR                [RFC7313]
           3-254   Unassigned
           255     Reserved            [RFC7313]

   In addition, this document defines a NOTIFICATION error code and an
   error subcode related to the ROUTE-REFRESH message.  IANA has changed
   the name of the "BGP Error Codes" to "BGP Error (Notification) Codes"
   and added this document as a reference.  IANA has allocated a new
   error code from that registry with the name "ROUTE-REFRESH Message
   Error", referencing this document.

   IANA has created a new registry for the error subcodes as follows:

           Under "Border Gateway Protocol (BGP) Parameters",
           under "BGP Error Subcodes":
           Registry: "BGP ROUTE-REFRESH Message Error subcodes"
           Reference: [RFC7313]
           Registration Procedure(s): Values 0-127 Standards Action,
             values 128-255 First Come First Served

           Value   Name                     Reference
           0       Reserved                 [RFC7313]
           1       Invalid Message Length   [RFC7313]
           2-255   Unassigned








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7.  Security Considerations

   Security considerations are given in [RFC4272] , but they do not
   cover Route-Refresh and many other BGP extensions.  This document
   does not significantly change the underlying security issues
   regarding Route-Refresh, although improved error handling may aid
   operational security.

8.  Acknowledgements

   The authors would like to thank Pedro Marques, Pradosh Mohapatra,
   Robert Raszuk, Pranav Mehta, Shyam Sethuram, Bruno Decraene, Martin
   Djernaes, Jeff Haas, Ilya Varlashkin, Rob Shakir, Paul Jakma, Jie
   Dong, Qing Zeng, Albert Tian, Jakob Heitz, and Chris Hall for their
   review and comments.  The authors would like to thank John Scudder
   for the review and contribution to this document.

9.  Normative References

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

   [RFC2918]  Chen, E., "Route Refresh Capability for BGP-4", RFC 2918,
              September 2000.

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

   [RFC4272]  Murphy, S., "BGP Security Vulnerabilities Analysis", RFC
              4272, January 2006.

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

   [RFC5291]  Chen, E. and Y. Rekhter, "Outbound Route Filtering
              Capability for BGP-4", RFC 5291, August 2008.

   [RFC5492]  Scudder, J. and R. Chandra, "Capabilities Advertisement
              with BGP-4", RFC 5492, February 2009.











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Authors' Addresses

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

   EMail: keyupate@cisco.com


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

   EMail: enkechen@cisco.com


   Balaji Venkatachalapathy

   EMail: balaji_pv@hotmail.com




























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