The MPLS WG Archive

[Mark Duffy <mduffy@quarrytech.com>]

Hi,

RFC 3036 (LDP) defines 2 types of peer discovery: Basic and Extended.

Basic cannot be used on non-multicast-capable NBMA interfaces (e.g. non-LC 
ATM or frame relay).

Extended can work on NBMA but unfortunately its semantics are different 
than Basic discovery: it allows "discovery" of peers that are more than 1 
hop away, and it does not bind the Hello adjacency to a particular 
interface.  Both of these differences can be undesirable in a context where 
one is looking to use LDP to distribute outer labels with adjacent peers on 
a non-LC NBMA network.  Extended discovery appears to be primarily intended 
for distributing "inner" labels with non-adjacent peers.

I have not seen any discussion of this in RFC 3036 or on this list.  Are 
folks out there deploying LDP over non-LC ATM or FR multipoint 
networks?  What type of discovery is being used?

It would seem to me that there is a need for a discovery method that is 
semantically similar to basic discovery, but that can operate on NBMA 
environments that lack multicast capability.  Any opinions on this?

Thanks,
Mark Duffy