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doubt in LDP Label Mapping procedure.

  • From: Abhijit <gabhijit@ee.iitb.ernet.in>
  • Date: Wed, 2 Aug 2000 16:25:15 +0530 (IST)



Hi all,

In the ldp-06 draft in Appendix A, in procedure of label mapping message,

LMp. 14 says is the LSR ingress for FEC?

How an LSR can know beforehand that it is ingress for a particular FEC? A
particular LSR can be egress for a particular FEC, but whether it is
ingress or not is dependent upon the source from where packet is entering
MPLS domain. 

Consider

         A-----------B-------------D
                     |
         C___________|


Here let a set of 4 routers A, B, C, D be the MPLS domain. When packet
enters this domain through A , A is the ingress and when it enters through
C, C is the ingress, If there is also a link between A & C and
shprtest path to B from A is via C, C will be ingress for a set of packets
but it won't be ingress for other set of packets, So how can you decide 
beforehand that C is ingress or not?

-abhijit