[c-nsp] 6500 dbus usage

[Tim Stevenson]

Hi Jon, please see inline below:

At 07:23 AM 9/20/2011, Jon Marshall contended:

>Thanks  Peter
>
>If they do have dbus connectors then why are they not supported with a sup32.


The connection to the dbus is a control path only on 67xx cards, 
there is no data path there. 67xx cards always use the fabric for 
data plane forwarding. It's just a question of whether the lookup 
happens centrally via the dbus or locally via a DFC.

Sup32 does not have any fabric connection, so there would be no way 
for traffic ingressing a 67xx card to reach the sup, or for sup 
traffic to egress a 67xx front panel port.


>  I thought it was a physical connectivity issue but apparently not. 
> So is it just a performance decision made by Cisco


Don't worry, unlike most other things on this list seemingly, there's 
not a conspiracy here. :P


Hope that helps,
Tim



>?
>
>Jon
>
>
> > Subject: Re: [c-nsp] 6500 dbus usage
> > From: peter at rathlev.dk
> > To: jms.123 at hotmail.co.uk
> > CC: cisco-nsp at puck.nether.net
> > Date: Tue, 20 Sep 2011 16:15:38 +0200
> >
> > On Tue, 2011-09-20 at 14:12 +0100, Jon Marshall wrote:
> > > My confusion is when i read on here that when the 67xx modules are
> > > running in CFC mode they send a portion of the packet (depending on
> > > compact/truncated mode) across the 32Gbps bus to the supervisor for a
> > > forwarding decision to be made. But if they don't have connectors to
> > > the 32Gbps bus then how do they access it ?
> >
> > They do have DBus connectors. Even the WS-X6708-10G-3C, even though the
> > diagram doesn't show it.
> >
> > 
> <http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps708/prod_white_paper0900aecd80673385.html#wp9000639>http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps708/prod_white_paper0900aecd80673385.html#wp9000639
> >
> > > As a further question, assuming they do send lookups across the shared
> > > bus then having classic linecards using the same bus could have a
> > > direct impact on the performance of the 67xx modules ?
> >
> > AFAIK it will not impact the performance of traffic staying on
> > fabric-enabled cards.
> >
> > (I'm not aware of any changes the Sup2T might introduce here.)
> >
> > --
> > Peter
> >
> >
>
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Tim Stevenson, tstevens at cisco.com
Routing & Switching CCIE #5561
Distinguished Technical Marketing Engineer, Cisco Nexus 7000
Cisco - http://www.cisco.com
IP Phone: 408-526-6759
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