[c-nsp] WS-X6704-10GE, WS-X6708-10GE

[Łukasz Bromirski]

On 2012-03-05 14:10, tao wrote:

>     Both 6704 and 6708 have two complex of Fabric ASICs.
>     The 6708 you can see on figure 21 here:
>     http://www.cisco.com/en/US/__prod/collateral/switches/__ps5718/ps708/prod_white___paper0900aecd80673385.html
>     <http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps708/prod_white_paper0900aecd80673385.html>
>
> suppose there are port A and port B belong to fabric channel 1 and port C
> belongs to fabric channel 2.
>
> how does traffic pass from port A to port B  with/without DFC ?

It goes up to the Port ASIC. CFC requests decision to be taken by
a PFC on the Supervisor and DFC can take the decision locally. It
is then looped back to port B. The CFC communication takes place
over the shared bus which is limiting factor for packets per second
(on each of it the CFC has to query PFC for decision). The limit
for such system is 15 or 30Mpps. The limit for DFC system is
48Mpps per linecard.

> and any difference for traffic passing from port A to port C ?

Yes, the CFC/DFC decision process will be the same, but the
traffic will leave the LC using channel 1, and then come back
to the LC using channel 2 to leave out of port C.

>   I am wondering whether the traffic pass through switch fabric ? Is switch
> fabric a passive component?

Passive in what sense? It doesn't do any network operations as is,
but it's powered up and processing traffic by means of frames +
additional headers. Switch fabric physically is a either a compex of,
or in the newer versions, single pretty large ASIC on the Supervisor
under the heatsink.

-- 
"There's no sense in being precise when |               Łukasz Bromirski
  you don't know what you're talking     |      jid:lbromirski at jabber.org
  about."               John von Neumann |    http://lukasz.bromirski.net