Subject: [mpls] Request for clarification on RFC 7552 (Updates to LDP for IPv6)

From: Ramakrishna Rao Desetti <[email-masked]>
Date: Fri, 22 Mar 2019 15:40:29 +0530

Hi,

I request a clarification on a specific point with regard to RFC 7552.

Section 8 says:

"Lastly, for better scale and optimization, an LSR may advertise only
 the link-local IPv6 addresses in the Address message, assuming that
 the peer uses only the link-local IPv6 addresses as static and/or
 dynamic IP routing next hops."

Link-local IPv6 addresses are specific to an interface/link. If we
learn link-local
IPv6 addresses via LDP session, how to assign to which interface this address
belongs to? Note that an LDP session may be backed up by multiple adjacencies on
parallel links between peers.

RFC 7552 already provided a mechanism to learn link local addresses of a peer
via hello messages. It correctly associates those addresses with an interface.
Given that it is not clear what is the motivation for the above mentioned
additional mechanism.

Thanks and regards,
Ramakrishna DTV.