RFC 1745 (rfc1745) - Page 2 of 19
BGP4/IDRP for IP---OSPF Interaction
Alternative Format: Original Text Document
RFC 1745 BGP4/IDRP for IP - OSPF Interaction December 1994
10. Appendix .................................................... 18
11. Authors' Present Addresses .................................. 19
1. Introduction
This document defines the various criteria to be used when designing
an Autonomous System Border Router (ASBR) that will run BGP4
[RFC 1654] or IDRP for IP [IDRP] with other ASBRs external to the AS,
and OSPF [RFC 1583] as its IGP.
All future references of BGP in this document will refer to BGP
version 4, as defined in [RFC 1654]. All reference to IDRP are
references to the Inter-Domain Routing Protocol (ISO 10747) which has
been defined by the IDRP for IP document [IDRP] for use in Autonomous
Systems.
This document defines how the following fields in OSPF and attributes
in BGP/IDRP are to be set when interfacing between BGP/IDRP and OSPF
at an ASBR:
IDRP came out of the same work as BGP, and may be consider a follow
on to BGP-3 and BGP-4. Most fields defined in the interaction
between BGP and IDRP are named the same. Where different, the IDRP
fields are shown separately.
BGP/IDRP MULTI_EXIT_DISC
BGP ORIGIN and AS_PATH/AS_SET vs. OSPF tag
IDRP EXT_INFO and RD_PATH/RD_SET
BGP/IDRP NEXT_HOP vs. OSPF Forwarding Address
BGP/IDRP LOCAL_PREF vs. OSPF cost and type
IDRP contains RD_PATH and RD_SET fields which serves the same purpose
as AS_PATH and AS_SET fields for IDRP for IP. In this document, we
will use the terms PATH and SET to refer to the BGP AS_PATH and
AS_SET, or the IDRP RD_PATH and RD_SET fields respectively, depending
on the context of the protocol being used.
Both IDRP and BGP provide a mechanism to indicate whether the routing
information was originated via an IGP, or some other means. In IDRP,
if route information is originated by means other than an IGP, then
the EXT_INFO attribute is present. Likewise, in BGP, if a route
information is originated by means other than an IGP, then the ORIGIN
attribute is set to or . For the purpose of this
document, we need to distinguish between the two cases:
Varadhan, Hares & Rekhter