[c-nsp] NPE-G1 PPS limitations

[Arie Vayner (avayner)]

The way the buses are built on the 7200 create a bandwidth bottle neck
for the PA slots. I would say 400M is the limit per bus (there are 2,
and the PAs are split between them).
You should be aware of the concept of bandwidth points with regards to
PA slots on 7200:
http://www.cisco.com/en/US/prod/collateral/routers/ps341/prod_presentati
on09186a008009184d.pdf
http://www.cisco.com/en/US/docs/routers/7200/configuration/7200_port_ada
pter_config_guidelines/3875In.html

On NPE-G1/G2, the onboard (on the NPE) GigE ports are different, and are
not limited by this kind of configuration as they are wired directly to
the forwarding engine.
There is also another exception for adding another PA slot on NPE-G1/G2,
by using the Jacket Card:
http://www.cisco.com/en/US/docs/routers/7200/configuration/7200_port_ada
pter_config_guidelines/3875In.html#wp1100537
http://www.cisco.com/en/US/prod/collateral/routers/ps341/prod_bulletin09
00aecd80471892.html

Arie

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Hank Nussbacher
Sent: Friday, April 18, 2008 07:28 AM
To: Ross Vandegrift
Cc: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] NPE-G1 PPS limitations

On Thu, 17 Apr 2008, Ross Vandegrift wrote:

> On Thu, Apr 17, 2008 at 11:35:13AM -0700, dpinkard at AccessLine.com
wrote:
>> Would one expect gigE to gigE traffic local to the NPE-G1 to scale 
>> higher than that?
>
> Yea, I would expect that.  I don't understand all of the 
> architechtural issues on the 7200 series in great detail, but it seems

> that either the PCI bus that line cards use isn't really up to doing 
> GigE, or the controllers on the PA-GE doesn't scale well.
>
> The router I saw this on originally had it's primary ingress interface

> on the NPE and primary egress interface on the PA-GE.  When we swapped

> a low-traffic interface on the NPE with the PA-GE, we suddenly saw our

> packet loss drop to nothing.  So I can say with pretty much 100% 
> confidence that local to the NPE will scale much better than the 
> PA-GE.
>
> Ross

Have others found this as well?  So far we have used the builtin GE
ports on the G1 and have not seen problems.  We are planning on adding a
4th GE port via a PA-GE and had not seen any documentation about the
limitations you mention.

Thanks,
Hank
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