The MPLS-OPS Archive

[Aditya Chugh <Aditya@in.huawei.com>]

Title: RE: mpls question

Hi Tarig,
 To add to what Sidnie has said , each LSR in an MPLS domain is a superset of an IP Router
i.e all LSRs also support traditional IP forwarding
The MPLS label is on the outside....and the IP header is inside.
At the time of data forwarding , the MPLS label is looked at.
The LSR should not even need to look at the destination IP address.
The efficiency of the forwarding paradigm provided by MPLS comes from the fact
that Labels have a small fixed  size.Therefore table lookup is much faster for labels( where we are looking for an exact match)as compared to finding the longest prefix match in case of IP forwarding.

But this is not the major driver for MPLS technology currently because
in most implementations data forwarding is done in Hardware(because of the higher speeds possible).
I think the major benefits of MPLS lie in its ability to provide traffic-engineering,QoS,constraint based routing etc
HTH,
Aditya

-----Original Message-----
From: tarig ballal [mailto:tarigb@yahoo.com]
Sent: Thursday, March 22, 2001 4:04 PM
To: mpls-ops@mplsrc.com
Subject: mpls question

Hi,
   I have question.
When a packet comes into a router supporting both
MPLS and conventional IP forwarding,on processing,
will the IP address be looked at first?Or the presence
of a label is checked first?
    In both cases,doesn't this add to the processing
delay and thus decreases the efficiency of the
forwarding paradigm provided by MPLS?
  
  Thanks
  
 
 

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