Re: OSPFv2 Opaque LSAs in OSPFv3

[Kireeti Kompella <[e-mail]>]

Hi Alex,

> Hard to talk without seeing the draft, but what problem
> is it trying to address? I mean, we already have a more
> generic "opaque"-like mechanism in OSPFv3, why is it not
> enough?

True, we have a generic opaque mechanism in OSPF v3.  However,
if I want to do TE in OSPF v3, what do I put in the packet to let
you know that this is a TE LSA?  In particular, what function code
do I put in the LSA?  Should there be a new function code for each
'legacy' Opaque LSA?  Etc.

The draft (see below, sorry all for the spam) just grabs a single
LSA function code for 'OSPF v2 Opaque LSAs', but otherwise keeps
everything mostly the same.

Take a look -- fortunately, it shouldn't take more than a couple
of minutes :-)

Kireeti.
-------






Network Working Group                                        K. Kompella
Internet Draft                                          Juniper Networks
Updates: 2740                                               October 2002
Category: Standards Track
Expires: April 2003

                      OSPFv2 Opaque LSAs in OSPFv3
                  draft-kompella-ospf-opaquev2-00.txt

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

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Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.


Abstract

   This memo specifies how OSPF version 2 Opaque Link State
   Advertisements can be carried in OSPF version 3.











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Internet Draft        OSPFv2 Opaque LSAs in OSPFv3          October 2002


1. Introduction

   RFC 2370 [OPAQUE] describes the notion of an "opaque" Link State
   Advertisement (LSA) -- as the RFC says, an LSA that provides "a
   generalized mechanism to allow for the future extensibility of OSPF".
   This has certainly proved useful, for example in defining Grace LSAs
   [HITLESS] and OSPF v2 Traffic Engineering LSAs [OSPF-TE].  RFC 2370
   also defines the format that opaque LSAs take in OSPF version 2
   [OSPFv2], and defines three flooding scopes for such LSAs:
   link-local, area-local and Autonomous System (AS)-wide.

   OSPF version 3 [OSPFv3] inherently supports the notion of opaque LSAs
   in that the flooding scope of an LSA is explicitly stated in the LSA
   header.  OSPF v3 also specifies how LSAs with unrecognized function
   codes are to be handled.

   This memo specifies how OSPF version 2 opaque LSAs can be carried in
   OSPF version 3.  This allows the reuse of the specifications of OSPF
   v2 Opaque LSAs, as well as the code to support them, in OSPF v3.  In
   a nutshell, an OSPF v3 LS Function Code is defined to indicate that
   the LSA is of type OSPF v2 Opaque LSAs; the OSPF v3 Link State ID is
   formatted the same as in the OSPF v2 Opaque LSA; and the body of the
   OSPF v3 LSA is identical to the body of the OSPF v2 Opaque LSA.


2. Opaque LSAs

   An Opaque LSA in OSPF v2 is formatted as follows [OPAQUE, A.2]:

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |            LS age             |     Options   |    LS Type    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  Opaque Type  |               Opaque ID                       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      Advertising Router                       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      LS Sequence Number                       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         LS checksum           |           Length              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    +                                                               +
    |                      Opaque Information                       |
    +                                                               +
    |                              ...                              |




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Internet Draft        OSPFv2 Opaque LSAs in OSPFv3          October 2002


   The LS Type is 9, 10, or 11 depending on whether the Opaque LSA's
   flooding scope is link-local, area-local or AS-wide (respectively).

   The above OSPF v2 Opaque LSA is formatted as follows as an OSPF v3
   LSA:

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |            LS age             |1|X|Y|    OSPFv2 Opaque LSA    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         Link State ID                         |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      Advertising Router                       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      LS Sequence Number                       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |          LS checksum          |            Length             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    +                                                               +
    |                      Opaque Information                       |
    +                                                               +
    |                              ...                              |

   The U bit in the LS Type is set to 1.  The LS Function Code is set to
   10 [to be ratified by the OSPF WG], indicating that the LSA type is
   'OSPF v2 Opaque LSA'.  The XY bits are set to reflect the flooding
   scope:

       OSPFv2 Opaque
      LSA of LS Type   X Y
      --------------   ---
                   9   0 0
                  10   0 1
                  11   1 0

   The OSPF v3 LSA's Link State ID is formatted as one octet of Opaque
   Type, and 3 octets of Opaque ID (i.e., exactly as the Link State ID
   of the OSPF v2 Opaque LSA).

   The body of the OSPF v3 LSA is octet-for-octet identical to the OSPF
   v2 Opaque Information.








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Internet Draft        OSPFv2 Opaque LSAs in OSPFv3          October 2002


2.1. Processing OSPF v2 Opaque LSAs

   An OSPF v3 implementation encountering an LSA of type 'OSPF v2 Opaque
   LSA' MUST follow the rules regarding handling and flooding as defined
   by the U and XY bits, as defined in [OSPFv3].

   In addition, an OSPF v3 implementation MAY further process an OSPF v2
   Opaque LSA as an OSPF v2 implementation would, e.g., it might use a
   Grace-LSA to accomplish (or assist in) hitless restart of OSPF v3; or
   it might build a Traffic Engineering database using the opaque TE
   LSAs.  It is the intent of this memo to maximize code (and
   specification) reuse between OSPF v2 and OSPF v3 in this regard.


Normative References

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

   [OPAQUE] Coltun, R., "The OSPF Opaque LSA Option," RFC 2370, July
       1998

   [OSPFv2] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998

   [OSPFv3] Coltun, R., D. Ferguson, and J. Moy, "OSPF for IPv6", RFC
       2740, December 1999


Informative References

   [HITLESS] Moy, J., "Hitless OSPF Restart", work in progress

   [OSPF-TE] Katz, D., D. Yeung, and K. Kompella, "Traffic Engineering
       Extensions to OSPF Version 2", work in progress


Security Considerations

   The flooding and handling of LSAs has already been specified in the
   [OSPFv3]; this memo only defines a new LS Function Code, and the
   format of the LS body.  The OSPF v3 security mechanisms to prevent
   tampering and spoofing of LSAs suffice.









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Internet Draft        OSPFv2 Opaque LSAs in OSPFv3          October 2002


Acknowledgments

   Many thanks to Quaizar Vohra, with whom much of this was discussed.


Authors' Addresses

   Kireeti Kompella
   Juniper Networks, Inc.
   1194 N. Mathilda Ave
   Sunnyvale, CA 94089
   Email: [e-mail]


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Internet Draft        OSPFv2 Opaque LSAs in OSPFv3          October 2002


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