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Versions: 00                                                            
Network Working Group                                       Luca Martini
Internet Draft                                               Keyur Patel
Expiration Date: April 2007                           Cisco Systems Inc.







                                                            October 2006


                  Route Distinguisher Zero Value Usage


                   draft-martini-l3vpn-rd-zero-00.txt

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
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Abstract

   The behaviour that must be followed when an route distinguisher (RD)
   of value zero is received is not clearly defined in rfc4364. This
   document clarifies the use of an RD with a value of zero in the
   context defined in rfc 4364.




Martini & Keyur                                                 [Page 1]


Internet Draft     draft-martini-l3vpn-rd-zero-00.txt       October 2006




Table of Contents

    1        Specification of Requirements  ........................   2
    2        Introduction  .........................................   2
    3        RFC4364 definitions  ..................................   2
    3.1       Usage of RD value of zero  ...........................   3
    4        Full Copyright Statement  .............................   3
    5        Intellectual Property Statement  ......................   3
    6        IANA Considerations  ..................................   4
    7        Normative References  .................................   4
    8        Author Information  ...................................   4





1. 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.


2. Introduction

   This document refines the Route Distinguisher semantics detailed in
   [RFC4364]. The Route Distinguisher consist of an 8-byte value whose
   encoding is detailed in [RFC4364]. The Route Distinguisher is used in
   conjunction with VPN prefixes and VPN nexthops in VPN networks to
   solely allow one to create distinct routes to a common IPv4 address
   prefix.


3. RFC4364 definitions

   Currently in [RFC4364] section 4.3.2, the RD is used with a value of
   0 in the next hop field of the BGP NLRI. This is a special case that
   is allowed by the design.  In section 4.2 of [RFC4364], the enconding
   of the RD for type 0 is defines as a type field , and a value field.
   If the type field is 0, then the value field in interpreted as
   containing an autonomous system number (ASN), and a assigned Number
   subfield. The ASN cannot contain 0 as it is a reserved ASN number.







Martini & Keyur                                                 [Page 2]


Internet Draft     draft-martini-l3vpn-rd-zero-00.txt       October 2006


3.1.  Usage of RD value of zero

   Whenever the RD is used within the VPN nexthop field of the BGP NLRI,
   the RD is used with the value of 0. However whenever the RD is used
   with VPN prefix field of the BGP NLRI , the Route Distinguisher MUST
   never be used with the value of 0. Hence, VPN routes received with
   the Route Distinguisher value of 0 MUST be discarded with an
   appropriate error.


4. Full Copyright Statement

   Copyright (C) The Internet Society (2006).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights.

   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


5. Intellectual Property Statement

   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; nor does it represent that it has
   made any independent effort to identify any such rights.  Information
   on the procedures with respect to rights in RFC documents can be
   found in BCP 78 and BCP 79.

   Copies of IPR disclosures made to the IETF Secretariat and any
   assurances of licenses to be made available, or the result of an
   attempt made to obtain a general license or permission for the use of
   such proprietary rights by implementers or users of this
   specification can be obtained from the IETF on-line IPR repository at
   http://www.ietf.org/ipr.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights that may cover technology that may be required to implement



Martini & Keyur                                                 [Page 3]


Internet Draft     draft-martini-l3vpn-rd-zero-00.txt       October 2006


   this standard.  Please address the information to the IETF at ietf-
   ipr@ietf.org.


6. IANA Considerations

   This document has no IANA Actions.


7. Normative References

   [RFC4364]] "BGP/MPLS IP Virtual Private Networks (VPNs)"
        E. Rosen, Y. Rekhter, RFC 4364 February 2006


8. Author Information


   Luca Martini
   Cisco Systems, Inc.
   9155 East Nichols Avenue, Suite 400
   Englewood, CO, 80112
   e-mail: lmartini@cisco.com


   Keyur Patel
   510 McCarthy Blvd.
   Milpitas , CA, 95035
   e-mail: keyupate@cisco.com






















Martini & Keyur                                                 [Page 4]