Subject: draft-raszuk-ospf-bgp-peer-discovery-00.txt

From: Robert Raszuk <[email-masked]>
Date: Sun, 22 Jun 2003 23:13:20 +0200

Network Working Group                             Robert Raszuk (Editor)
Internet Draft                                        Cisco Systems, Inc
Category: Standards Track                                      June 2003
Expires: December 2003

                 OSPF Extensions for BGP Peer Discovery
              draft-raszuk-ospf-bgp-peer-discovery-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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Abstract

   This document proposed an extension to OSPF Router Information LSA
   [LINDEM1] to distribute selected information about BGP process on a
   router to other routers in the same area or in the same domain. Such
   information is required for network based auto discovery of IBGP
   peers as described in [IBGP-AM].

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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 [RFC2119].

2. Introduction

   Today all BGP peering configuration is manual and requires action on
   both sides. In IBGP Auto Mesh draft [IBGP-AM] we propose the
   automation of this task for IBGP sessions. As a distribution of
   required information OSPF [RFC2328] native flooding is being
   proposed.

   The information required to be flooded is static and can change only
   by operator's manual configuration.

   It is envisioned that in the future when new and better approaches
   for flooding information are available and deployed BGP Auto
   Discovery TLV could also be migrated from OSPF to be flooded over
   such a new transport.

3. The BGP Auto Discovery TLV

   BGP Auto Discovery TLV is proposed to be flooded inside OSPF Router
   Information LSA.

   The format of OSPF Router Information LSA is indicated for reference
   in Figure 1 as proposed in [LINDEM1]

    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   |   10 or 11    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       4       |                    0                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Advertising Router                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     LS sequence number                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         LS checksum           |             length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +-                            TLVs                             -+
   |                             ...                               |

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             Figure 1. OSPF Router Information LSA

   For the application of distribution of BGP Auto Discovery TLV only
   area wise flooding scope (code 10) and domain wide flooding scope
   (code 11) are applicable.

   As described in IBGP Auto Mesh document [IBGP-AM] BGP Auto Discovery
   TLV will have the format presented in figure 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   TLV Type    |    Length     |     FLOODING RESERVED     |F|D|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        BGP Identifier                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  FRAG |     BGP  RESERVED     |        16 bit CHECKSUM        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Autonomous System(s) or confederation sub-AS(s) sub-TLV    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             IPv4/IPv6  Peering Address sub-TLV                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             AFI/SAFI for mesh topologies sub-TLV              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          AFI/SAFI for reflection topologies sub-TLV           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   Old BGP Identifier sub-TLV (opt)            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                  Figure 1. BGP Auto Discovery TLV

   Type        One octet set to 2 (to be confirmed).
   Length      One octet indicating the length of the TLV

   Control Flags related to IGP operation:

   Symbol    Capabilities

   F         Flooding scope
   D         Down Bit
   Reserved  Set to all zeros

   "F" {flooding} flooding scope of this TLV, when set domain wide
       flooding scope is required (type 11), when not set TLV should
       not be flooded into other areas or levels (type 10). Default
       "F" not set indicating area wide flooding only (type 10).

   "D" {down} down bit is not relevant to OSPF and should be ignored by

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       OSPF. It is present in the BGP Auto Discovery TLV to achieve
       identical encapsulation syntax independent from flooding protocol
       being selected by the operator.

   The specific information and encoding of BGP sub-TLVs is discussed in
   [IBGP-AM].

4. Operation

   It should be important to emphasize the fact that OSPF interaction
   with the new information is to remain minimal. BGP component will
   prepare the necessary information to be flooded as well as keep the
   received information in it's own cache. BGP component will also
   inform OSPF about required flooding scope for it's information.

   OSPF role in new information interpretation is limited to selectively
   pass BGP Auto Discovery TLV to BGP component of the router. It is
   assumed that all global LSA comparisons will still take place. On the
   other hand it is not required that OSPF will try to parse and compare
   the TLV itself and based on the result initiate BGP notification or
   not. Added checksum field should make comparison done by BGP itself
   much less CPU intensive.

   Forced reflooding should only take place based on the manual
   configuration change. During normal network operation when BGP
   configuration related to peer maintenance is constant BGP Auto
   Discovery TLV should not cause any extra processing or flooding for
   OSPF.

5. Deployment Considerations

   The new proposed data to be flooded has an informational character.
   Routers which do not understand new information will not be able to
   participate in the IBGP auto mesh.

   Deployment of new code which supports new information can be
   incremental. Also enabling information distribution itself can have
   an incremental character.

   It should be up to operator's decision to switch from informational
   use of BGP Auto Discovery TLV to operational IBGP auto mesh benefits.

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6. IANA Considerations

   A new opaque LSA type for OSPF Router Information LSA will need to be
   assigned by IANA. Additionally, IANA will need to have registries for
   the OSPF Router Information opaque LSA TLVs.

   The TLV assignee will be responsible for allocation of any sub-TLVs
   for the IANA assigned TLV.

7. Security Considerations

   It is highly encouraged to use existing OSPF security mechanism when
   transporting BGP Auto Discovery TLV [RFC2328]. While addition of new
   information does not present any additional risks injection of not
   authorized OSPF Router Information LSAs containing unreal BGP Auto
   Discovery TLVs could require an implementation of additional
   filtering before attempting to establish IBGP sessions.

8. Acknowledgments

   I would like to express special thanks to Abhay Roy & Peter Psenak
   for their comments.

9. Normative References

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

   [RFC2434]  Narten, T., Alvestrand, H., "Guidelines for Writing an
       IANA Considerations Section in RFCs", RFC 2434, October 1998.

10. Informative References

   [IBGP-AM]  Raszuk, R., "IBGP Auto Mesh", draft-raszuk-ibgp-auto-
       mesh-00.txt, June 2003

   [LINDEM1]  Lindem, A. at all, "Extensions to OSPF for Advertising
       Optional Router Capabilities", draft-lindem-ospf-cap-00.txt, May
       2003

   [RFC2328]  J. Moy. OSPF version 2. Technical Report RFC 2328,
       Internet Engineering Task Force, 1998.

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11. Authors' Addresses

      Robert Raszuk
      Cisco Systems, Inc.
      Al. Jerozolimskie 146C
      02-305 Warsaw, Poland
      Email: [email-masked]

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14. Full Copyright Notice

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