Hi, Jim and All: Here is another simple example that can prove current UPA don't work. Let's image one normal topology:
PE1(area 1)----ABR1---P2(area 0)----ABR2---PE2(area 2) When one prefix P0 on PE2 in area 2 became unreachable, according to the current procedure, ABR2 will generate the UPA signal. The UPA signal will be flooding within area 0. But such UPA signal can't pass ABR1, then PE1 in another area can't get the unreachable information. PE1 can't do any switchover action based on the expected UPA signal. Current UPA proposal is broken in cross-area scenario. Best Regards Aijun Wang China Telecom -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Thursday, June 5, 2025 3:46 PM To: [email protected] Cc: [email protected] Subject: [Lsr] I-D Action: draft-ietf-lsr-igp-ureach-prefix-announce-08.txt Internet-Draft draft-ietf-lsr-igp-ureach-prefix-announce-08.txt is now available. It is a work item of the Link State Routing (LSR) WG of the IETF. Title: IGP Unreachable Prefix Announcement Authors: Peter Psenak Clarence Filsfils Daniel Voyer Shraddha Hegde Gyan Mishra Name: draft-ietf-lsr-igp-ureach-prefix-announce-08.txt Pages: 15 Dates: 2025-06-05 Abstract: Summarization is often used in multi-area or multi-domain networks to improve network efficiency and scalability. With summarization in place, there is a need to signal loss of reachability to an individual prefix covered by the summary. This enables fast convergence by steering traffic away from the node which owns the prefix and is no longer reachable. This document describes how to use the existing protocol mechanisms in IS-IS and OSPF, together with the two new flags, to advertise such prefix reachability loss. The IETF datatracker status page for this Internet-Draft is: https://datatracker.ietf.org/doc/draft-ietf-lsr-igp-ureach-prefix-announce/ There is also an HTMLized version available at: https://datatracker.ietf.org/doc/html/draft-ietf-lsr-igp-ureach-prefix-announce-08 A diff from the previous version is available at: https://author-tools.ietf.org/iddiff?url2=draft-ietf-lsr-igp-ureach-prefix-announce-08 Internet-Drafts are also available by rsync at: rsync.ietf.org::internet-drafts _______________________________________________ Lsr mailing list -- [email protected] To unsubscribe send an email to [email protected] _______________________________________________ Lsr mailing list -- [email protected] To unsubscribe send an email to [email protected]
