The MPLS WG Archive

[Bob Thomas <rhthomas@cisco.com>]

Hi Bruno,

> Hi Pranjal, all,
> 
> That's a good question; thanks for asking ;-)
> 
> Currently, as per RFC 3036 section 3.5.7.1, Ru should perform a longest =
> match.

I think you meant exact match.

  draft-ietf-mpls-rfc3036bis-03.txt:

   An LSR receiving a Label Mapping message from a downstream LSR for a
   Prefix SHOULD NOT use the label for forwarding unless its routing ta-
   ble contains an entry that exactly matches the FEC Element.
                              ***************


Bob


> But we believe that in some situation (eg use of IGP areas), we could =
> benefit from doing a longest match as this would relax the need for =
> leaking in the IGP all the /32 prefixes across area boundaries. To =
> initiate discussion on this point, we've written =
> draft-decraene-mpls-ldp-interarea-01.txt and presented it in Vancouver ( =
> http://www3.ietf.org/proceedings/05nov/slides/mpls-4.pdf )
> 
> Right after this presentation, it was suggested to gather feed-back on =
> the usefulness of this ID before moving forward.=20
> 
> Pranjal, all, could you please tell us whether you think that it is =
> worth being pursed?
> 
> 
> Best regards,
> Bruno
> 
> 
> 
> ________________________________________
> From: Dutta, Pranjal [mailto:pdutta@riverstonenet.com]=20
> Sent: Saturday, April 08, 2006 10:11 PM
> To: mpls@ietf.org
> Subject: [mpls] One LDP Implementation specific question of receive =
> labelmapping for prefix FECs
> 
> Hi,
> =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 I have a basic confusion on =
> the "Label Mapping Receive Procedure" explained in the appendix of RFC =
> 3036. One step says "Find the FEC next hop". 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 =A0prefix at Ru. The reason why I am asking is I guess the =
> implications could be different based on whether LSR is merge capable or =
> non-merge capable.
> 
> Thanks in advance,
> Pranjal
> 
> 
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