[c-nsp] 7609-S Throughput

[Mack McBride]

I probably wrote some of those over-subscription posts regarding the 6500 and 6704 which is the same backplane.
The backplane has some overhead that will limit what you can do.
Once you go over 80% on the backplane (32G total/16G per channel in one direction) you can run into some serious issues.
You start losing control messages and the machine can even restart if congestion is severe.
However if you have a significant quantity of traffic in one direction (likely at these levels of traffic),
You can pair ports (in and out) so that backplane congestion is does not occur.
If oversubscription is a serious issue then on the 6708 and 6716 the situation is even more complicated.
Specifically on the 6708 the port layout is far from obvious. Research the archive for the layout.

LR Mack McBride
Network Architect


-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Gert Doering
Sent: Tuesday, February 14, 2012 9:37 AM
To: James Bensley
Cc: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] 7609-S Throughput

Hi,

On Tue, Feb 14, 2012 at 03:53:50PM +0000, James Bensley wrote:
> I've heard that 10Gig cards in a 7609-S won't be able to push 10Gig of 
> traffic down the port. Apparently the line cards will go at wire speed 
> but the chassis won't push 10Gig across the back plane between say two 
> 10Gig ports on two different cards. I've never used 10Gb modules on 
> these chassis before, can anyone here say if they have had any 
> problems with this, or perhaps adversely they easily max out their 
> 10Gig ports on their 7600's?

Someone once told me a rumor, saying that an archive of cisco-nsp exists, and that this might be a fairly frequent topic...  (and that the answer is somewhat complex, depending on card, local switching or cross-fabric, and on 6708's and 6716's, port distribution).

Short answer: 6700 cards have a 40 Gbit fabric connection.  There is some overhead to it, so you can't run all 4 ports at 4x10 gbit line rate, but something like 3.5x 10G should be doable on a 6704.  6708 and 6716 cards are overbooked - they will handle 10G on each individual port, but not on all of them at the same time, and not on arbitrary combinations.

gert

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