[j-nsp] New 16port 10G Card and new MPC with 4x10G MIC Cards - coexistance of old DPCs and new Cards in same chassis -- looking for experience feedback

[Richard A Steenbergen]

On Sun, Aug 29, 2010 at 12:00:01PM -0700, Derick Winkworth wrote:
> so the possibility does exist that with a combination of newer fabric 
> and newer line card (a line card with better MQ memory bandwidth), 
> that MX might be able to push more traffic per slot...

Sure, the chassis backplane is electrically capable of quite a bit, so 
if you keep upgrading the fabric and the cards you should be able to 
keep increasing bandwidth without forklifting the chassis for a long 
time.

BTW, one more point of clarification on the MQ bandwidth limit. The 70G 
limit is actually the for bandwidth crossing the PFE in any direction, 
so the previously mentioned "35G fabric 35G wan" example is actually 
based on the assumption of bidirectional traffic. To calculate the MQ 
usage you only want to count the packet ONCE per PFE crossing (so for 
example, you can just count every ingress packet), but you need to 
include traffic coming from the fabric interfaces too.

So for example:

* A single 10Gbps stream coming in one port on the PFE counts as 10Gbps 
of MQ usage, regardless of whether it is destined for the fabric or for 
a local port.

* A bidirectional 10Gbps stream between two ports on the same PFE counts 
as 20Gbps of MQ usage, since you have 2 ports each receiving 10Gbps.

* 30Gbps of traffic coming in over the fabric (ignoring any fabric 
limitations for the moment, as they are a separate calculation) and 
going out the WAN interfaces counts as 30G of MQ usage, which means you 
still have another 40G available to receive packets from the WAN 
interfaces and locally or fabric switch them.

This is quite a bit more flexible than just thinking about it as "35G 
full duplex", since you're free to use the 70G in any direction you see 
fit.

-- 
Richard A Steenbergen <ras at e-gerbil.net>       http://www.e-gerbil.net/ras
GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)