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Layer 3 Lookup in ATM LSR's

  • From: "Gray, Eric" <egray@celoxnetworks.com>
  • Date: Tue, 6 Aug 2002 10:01:52 -0400
  • Cc: David Charlap <David.Charlap@marconi.com>, "Mpls (E-mail)" <mpls@UU.NET>

Giles,

	I think your point is valid, however, I also
think David was making a reasonable simplification
- logically, if the ingress interface 'pops' the
label it would do so so that it can perform a new
lookup on either the next label, or the IP header
(if the popped label was the last label).

Eric W. Gray
Systems Architect
Celox Networks, Inc.
egray@celoxnetworks.com
508 305 7214


-----Original Message-----
From: Giles Heron [mailto:giles@packetexchange.net] 
Sent: Tuesday, August 06, 2002 10:50 AM
To: David Charlap
Cc: IETF MPLS List
Subject: Re: Layer 3 Lookup in ATM LSR's

just one nit...

On Mon, 2002-08-05 at 19:02, David Charlap wrote:
[snip]
> Lookup capability is also needed for a router (or interface) that must 
> pop the label stack.  It must do a label-lookup (which all switches can 
> do), but it must then pop the stack and then do an IP lookup on the 
> result before forwarding.  This is beyond the capability of most ATM 
> forwarding hardware.
[rest snipped]

this isn't strictly, true - is it?

in some cases you may pop the stack but then forward the IP payload
without actually performing an IP lookup (e.g. PHP).

Giles

-- 
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Giles Heron    Principal Network Architect    PacketExchange Ltd.
ph: +44 7880 506185              "if you build it they will yawn"
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