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Cell Relay Retreat>MPLS WG Archive>month:2002-Oct> msg00137



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Does a labeled packet go through "Packet Filtering/Policy Routing/FilterBased Forwarding"?

  • From: David Charlap <David.Charlap@marconi.com>
  • Date: Thu, 24 Oct 2002 12:42:00 -0400
  • User-Agent: Mozilla/5.0 (Windows; U; WinNT4.0; en-US; rv:1.1) Gecko/20020826

Sachin Kalra wrote:
> 
> A quick question. Does a labeled packet go through "Packet 
> Filtering/Policy Routing/Filter Based Forwarding"?

What would you have it filter on?  A transit router should not make 
forwarding decisions based on anything other than the topmost label.  If 
you start drilling down into the packet payload to make these decisions, 
then why bother using MPLS at all?

One of the key reasons for MPLS these days is the ability to optimize 
traffic engineering.  You will decide your route through the network 
when you set up the LSP.  The node at the LSP's ingress will decide 
which packets to forward into which LSP.  Once that decision is made, 
the packets should not be examined again until they emerge from the 
other end of the LSP.

-- David