[c-nsp] Cisco 6509 and Bus speeds

[Michael Loftis]

--On Thursday, January 13, 2005 08:51 -0800 Tim Stevenson 
<tstevens at cisco.com> wrote:

> See below:
...
> It is a 16G (32G marketing) bus. If you don't have DFCs, it is used to
> xfer packet headers to the sup for lookups, with DFCs, it is not used. In
> either case, the fabric channels, not the 16G bus, are used to xfer the
> actual packets/payload.
>
>> and therfor you shouldn't be able to transfer more then
>> 8Gbps from one slot to another, or am I wrong in this one?
>
> Wrong, with the cards you mention you have 2x20G (40G marketing) channels
> to each card (40G per slot, 80G marketing), except the 6724 (1x20G
> channel). These all interconnect thru the fabric on the sup.
...

What may not have yet been made clear is the 6509 has fabric and bus.  the 
bus is rated at 2x8G (bi directional) and the fabric is 2x20G (also bi 
directional i believe)...  this is where the 'marketing' numbers Tim 
mentions come from.

It does require DFC3 to achieve these rates, and DFC and DFC3 are NOT the 
same beast.  More confusing cisco terminology :)  the DFC3 is the child of 
DFC/next generation of the DFC board.

The fabric is used for the actual packet/payload, the bus is used to 
transfer control information, headers, location, and update the dCEF/CEF 
tables across the switch, as well as management traffic inside the switch.

I hope that helps to clear things up a bit....I also hope I didn't muddy 
things further by being incorrect :)

One thing of note, it may no longer be a problem though so YMMV, but don't 
run ANY traffic on the default/native VLANs on the cat's.  Everything the 
RSP and SUP gets ends up punted to the processor on the default/native VLAN 
(usually vlan 1) -- this destroys performance.  Only thing VLAN1 should be 
used for is switch management traffic and switch spanning-tree 
information/etc.