The MPLS WG Archive

[Bob Thomas <rhthomas@cisco.com>]

Manoj,

>  I have seen lot of discussions on this topic. Could somebody give me
> clarification on the following :-
> 
> 1) An upstream LSR Ru send a label request (assuming DOD is being used)
> to LSR Rd. This request comatins a set of fec elements for which it is
> known that Rd is next hop for Ru.  Now, what should Rd 's response be if

Please note the following from Section 3.4.1 of RFC3036:

      Note that this version of LDP supports the use of multiple FEC
      Elements per FEC for the Label Mapping message only.  The use of
      multiple FEC Elements in other messages is not permitted in this
      version, and is a subject for future study.


Bob


> these set of fec elements cannot be mapped to a single next hop from Rd.
> Should it :
> a) Break the request into sets of fec elements for which the next hop
> from Rd is same and send
>     multiple mappings to Ru (one for each such set).  If that is so,
> should it use the same msg id for all the
>     responses (same as request msg id). If this is the case, then only
> the first such label mapping message will be accepted by Ru as it will
> match a sent request (which will be deleted after receiving this
> mapping).
> All subsequent mappings will be rejected as they seem to be unsolicited
> mappings from Rd to Ru, there being no record of a matching request)
> 
> b) Send a single mapping to Ru and just do label stripping when such a
> labelled packet comes from Ru.
> 
> c) Send a NULL label (what if Ru does not support label popping ??)