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Cell Relay Retreat>MPLS WG Archive>month:2001-Feb> msg00196



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Hop Count Procedures

  • From: "B, Prakash K (Prakash)" <prakashk@lucent.com>
  • Date: Tue, 20 Feb 2001 15:25:56 +0530


ATM LSRS do not perform TTL decrement. RFC 3036 says that while propogating
the label mapping message upstream, if an LSR (Rd) finds out that its
upstream LSR (Ru) is a part of domain that does not perform TTL
decrement(ATM segment), it must reset the Hop Count value to 1. Will this
not lead to erroneous computation of final TTL in the long run when the
packet exits out of MPLS domain?Will not the true Hop count value assist the
ingress in determining in advance the TTL value that must be, when the
packet emerges out of a Non -TTL-decrement segment?

RFC 3031 clearly states that the final TTL value must reflect the true
number of hops that a packet takes to exit a MPLS domain .
Clarification solicited.

Prakash K.B.