Subject: [Lsr] Questions on Prefix Unreachable Announcement

From: Huaimo Chen <[email-masked]>
Date: Fri, 20 Dec 2019 14:50:09 +0000

Hi Aijun,

    My understanding of your draft https://datatracker.ietf.org/doc/draft-wang-lsr-prefix-unreachable-annoucement/ as follows:
    After the ABR originates the Extended Prefix Opaque LSA, which contains a prefix and its originator (i.e., the router originating the prefix), it will announce that the prefix is unreachable when it can not reach the prefix (i.e., the prefix becomes unreachable from reachable from the ABR's perspective).
     Is my understanding right?

    Should the ABR remove the prefix from the Extended Prefix Opaque LSA after it announces the prefix unreachable for a give period of time? After a router in another area receives the unreachable announcement of the prefix, it installs a black hole route to the prefix, and then removes the black hole route after a configurable time. After the black hole route derived from the unreachable announcement of the prefix is removed, it seems better to remove the unreachable prefix from the LSA.

     Can the ABR just remove the prefix (i.e., the TLV for the prefix) from the Extended Prefix Opaque LSA when it can not reach the prefix?

Best Regards,
Huaimo