[c-nsp] why vpls need some special line cards to support

[Arie Vayner (avayner)]

In VPLS, we need to be able to perform two actions:
- L2 forwarding based on MAC (consider there could be local switching,
need to perform MAC learning, flooding etc)
- Label imposition

Older PFC (forwarding engine on 6500/7600) cannot perform both actions
in the same hardware, so another resource is required.
PFC would perform the L2 forwarding functions (like a regular L2 switch
would do), and the egress linecard would perform the label imposition.

Regular LAN linecards do not have forwarding capacity on them (even if
they have a DFC), and would require a more advanced line card.
These are the different SIP modules or more recently ES20 and ES+
modules (now also supported on 6500...)

On 6500, SUP2T can also do VPLS natively, because the new PFC (PFC4) can
do all the processing on its own.

Arie

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of ying-xiang
Sent: Monday, January 09, 2012 17:27
To: cisco-nsp at puck.nether.net
Subject: [c-nsp] why vpls need some special line cards to support

i have been confused by this question for a long time and i have been
looking up some stuff from CCO.but still can not find the answer.what's
the difference between when a router need to  handle encapsulation of
L3VPN and L2vpn?anyone who could give the point?
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