[c-nsp] Cisco 6509 and Bus speeds

[Colin Whittaker]

On Thu, Jan 13, 2005 at 01:45:03PM +0100, Marcel Lemmen wrote:
> Hi all,
> 
> My company is looking for a replacement of our Cisco 4006 and we're
> looking at the 6509 with Sup720. I do however have some questions
> regarding the Bus and backplane speeds which are a bit unclear to me.
> Perhaps somebody could help me with this one.
> 
> We are looking for a configuration with a Sup720, 2x 4 port 10GE
> line-cards, a 48port 10/100/1000 and a 24port 1GigE SFP.
> 
> I have some nasty experiences with promised performance and actual
> performance, like a 7500 with GEIP+ witch only handles 400Mbit/s, a 4006
> switch with 3x24Gbit/s SwitchEngines and gives packetloss at 1.8Gbp/s etc.
> 
> The c6509 with Sup720 can handle 720Gbps of switching traffic in total,
> but what happens if I transfer 40Gbps from one slot to the other slot with
> 4x10GE (since we have 8 10GE ports)? As far as I know the c6509 has a
> 8Gbps backplane and therfor you shouldn't be able to transfer more then
> 8Gbps from one slot to another, or am I wrong in this one? Using dCEF it
> would be possible to transfer 40Gbps of traffice within one slot but not
> between slots or not?
> 
> Could someone explain this to me because I want to know a bit more about
> the architecture so I won't make the same mistake as I did earlier :)

With the sup720 there is 720Gbps of switching capacity in the fabric,
which is seperate to the shared backplane. The shared backplane is still
used for sending data to and from the Sup which is where the 32M PPS is
from, with framing overhead on 32Million packet headers can be bumped to
the supervisor. With DFCs on the line cards these headers never leave
the card.

To Actually push 40Gbps between two slots you will need the DFCs.

Colin
-- 
Colin Whittaker    colin.whittaker at heanet.ie    Tel: +353 1 6609040
HEAnet NOC         noc at heanet.ie                iNOC-DBA:  1213*752