Subject: [mpls] LDP Entity Table in RFC 3815

From: Alexander Vainshtein <[email-masked]>
Date: Mon, 17 Nov 2014 14:06:21 +0000

Loa, George, Ross and all hi,
I apologize in advance for a possibly naïve question, but I have, so far, failed to understand what is represented by individual entries in the LDP Entity  Table in RFC 3815.

One possible interpretation is that  a given node and for a given LDP Identifier, would typically support up to two entries in the table:

·         One entry would be responsible for all direct sessions (and hence the value of Targeted Peer in this entry would be set to False)

·         Another entry would be responsible for all targeted sessions (with the value of Targeted Peer set to True)

·         Each entry would be explicitly created by a suitable management operation (using the Row Status)

·         Multiple peers (each with its own sessions) would be associated with each entity (as suggested by indexing  for the LDP Peer Table).

Yet another possible interpretation is that a separate LDP Entity could be created for each interface on which LDP is enabled. This is suggested by the statement in description of mplsLdpEntityIndex that says that ifIndex (presumably of an interface on which LDP has been enabled) may be used as the LDP Entity Index.  This interpretation does not contradict the previous one, because it could refer to "real" interfaces for direct sessions and to loopback interfaces for targeted sessions. This interpretation would also facilitate adding/removing LDP-enabled interface to/from a node. However, this interpretation does not sit well with the definition of the next free index for the LDP Entity table.

However, neither of these interpretations looks compatible with the following text from the definition of Admin Status of the LDP Entity Table entry:

             If this object is changed from 'enable' to 'disable'
             and this entity has already attempted to establish
             contact with a Peer, then all contact with that
             Peer is lost and all information from that Peer
             needs to be removed from the MIB.

The fact that "Peer" (highlighted in this text) appears in singular strongly suggests that a single entry in the LDP Entity table corresponds to at most one peer.

Any clarifications on the subject would be highly appreciated.

Regards, and lots of thanks in advance,
Sasha

Regards,
       Sasha
Email: [email-masked]
Mobile: 054-9266302