The MPLS WG Archive

["Dutta, Pranjal" <pdutta@riverstonenet.com>]

Hi Eric,
          As per RFC 3036 Label mapping receive procedures, when Ru
received a label mapping from Rd for a FEC x, Ru need to find an "exact"
match of the FEC x(IPv4/V6 prefix) in its route table. In Inter-IGP-area
or inter-AS case the routes from Rd would be summarized to Ru and in
such a case Ru MAY not find the exact match for such FEC x. In terms of
RFC 3036 then Ru MAY not find exact match for the FEC received from Rd
in its route table and no further action at Ru. My question was why Ru
can't we do a longest prefix match for the FEC x as LPM means it can be
reached by a downstream Rd? 

Thanks,
Pranjal

-----Original Message-----
From: Eric Rosen [mailto:erosen@cisco.com] 
Sent: Monday, 10 April, 2006 11:39 PM
To: Dutta, Pranjal
Cc: mpls@ietf.org
Subject: Re: [mpls] One LDP Implementation specific question of receive
label mapping for prefix FECs 


> When Ru receives a label mapping for a FEC of type IPv4/v6 prefix from
Rd,
> the next hop  for the FEC can be determined after  route lookup. Now
here,
> for looking  up the  FEC at Ru  do we  need to do  exact match  or
Longest
> prefix match? It is quite possible that the prefix as FEC mapped by Rd
may
> be within a supernetted prefix at Ru. 

It's a  little hard  to understand what  you're asking.  By  definition,
one
cannot change the FEC in mid-LSP.  If  the FEC is an address prefix, and
you
reach a  point where that address prefix  is not in the  routing table,
then
the LSP terminates. 



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