Subject: [Lsr] [Technical Errata Reported] RFC5185 (6506)

From: RFC Errata System <[email-masked]>
Date: Fri, 2 Apr 2021 05:29:31 -0700 (PDT)

The following errata report has been submitted for RFC5185,
"OSPF Multi-Area Adjacency".

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You may review the report below and at:
https://www.rfc-editor.org/errata/eid6506

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Type: Technical
Reported by: Ketan Talaulikar <[email-masked]>

Section: 2.7

Original Text
-------------
   Multi-area adjacencies are announced as point-to-point links.  Once
   the router's multi-area adjacency reaches the FULL state, it will be
   added as a link type 1 to the Router Link State Advertisement (LSA)
   with:

      Link ID = Remote's Router ID

      Link Data = Neighbor's IP Address or IfIndex (if the underlying
      interface is unnumbered).

   Unlike numbered point-to-point links, no type 3 link is advertised
   for multi-area adjacencies.

Corrected Text
--------------
   Multi-area adjacencies are announced as point-to-point links.  Once
   the router's multi-area adjacency reaches the FULL state, it will be
   added as a link type 1 to the Router Link State Advertisement (LSA)
   with:

      Link ID = Remote's Router ID

      Link Data = Router interface's IP Address or IfIndex (if the underlying
      interface is unnumbered).

   Unlike numbered point-to-point links, no type 3 link is advertised
   for multi-area adjacencies.

Notes
-----
The encoding of Link Data as specified in RFC5185 is not consistent with the base OSPF specification in RFC2328. This has resulted in different behaviors in deployed implementations where some follow RFC2328 (i.e. the corrected text) while others follow the Original text of RFC5185 leading to interop issues.

More importantly, for implementations of RFC5185, it is not possible to determine the Neighbor's interface IfIndex unless some additional mechanisms (that have not been specified or referenced by RFC5185) are implemented - viz. RFC8510.

This topic has been discussed in the LSR WG recently and this errata is being raised to track this issue : https://mailarchive.ietf.org/arch/msg/lsr/iL85WkrqhI17wUrxd-WozMQvKtE/

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RFC5185 (draft-ietf-ospf-multi-area-adj-09)
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Title               : OSPF Multi-Area Adjacency
Publication Date    : May 2008
Author(s)           : S. Mirtorabi, P. Psenak, A. Lindem, Ed., A. Oswal
Category            : PROPOSED STANDARD
Source              : Open Shortest Path First IGP
Area                : Routing
Stream              : IETF
Verifying Party     : IESG