[c-nsp] SFM and Sup720 and 7600

[Gert Doering]

Hi,

On Thu, Jan 19, 2006 at 03:48:28PM +0200, Kim Onnel wrote:
> Ok, now i understand that in 6500/7600 arch. a fabric is needed, so if you
> have Sup 1 or 2, u dont have fabric and you should purchase the SFM if you
> need to add more GE ports but if you have Sup720 then no SFM is needed for
> addition GE ports,

The 6500 switches have a "backplane bus", which is shared between all
cards, and an optional "fabric", which is a point-to-point interconnect,
given each card dedicated bandwidth.  I don't know the exact numbers
(how fast is the bus, how fast is the fabric) right now, but there are
good documents on www.cisco.com that explains all this.

> Whats the diff. between fabric-enabled or not modules ?

All modules can use the backbplane bus (as far as I understand).

If you have a fabric, only fabric-enabled modules will actually *use*
the fabric - "not fabric-enabled modules" will still use the backplane 
bus, and will not benefit from the fabric.

In addition, you can have modules that have "local brains" for L3 routing
decision - that's the "DFC" card (distributed <something>).  So your
supervisor won't have to do any work for packets forwarde by these modules.


> I really get confused with the switching terms, fabric, backplane,
> fabroic-enabled...
> 
> Any simple resource to understand this, other than Networkers slides ?

Hmmm, I have no URL at hand, sorry.  There are some good documents on
www.cisco.com (but yes, given the high number of 24-port-<something>
modules with and without fabric, with and without DFC, etc., all of this
is very confusing).

gert
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Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de