Switch specifications - Performance

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Sep 14th, 2009
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I have some very basic doubt regarding switch specifications / performance paramaters.

In performance capacity of switch specification • - it is mentioned : 160-Gbps switching fabric capacity : what does this mean?

How it is mentioned on chasis switches?

As in chasis switch all cards are installed on same backplane ( like PC motherboard ).

Please share the experience.

Any link on cisco or any other website to understand these terms is highly appreciable.

Thanks in advance


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Giuseppe Larosa Mon, 09/14/2009 - 08:53
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Hello Subodh,

several threads about this exist in the forums with excellent explanations.

It can be helpful to read C6500 architecture whitepaper.


These high end switches have a switching matrix that allow them in the best cases non blocking communications between linecards.

In the case of C6500 we need to distinguish between:

shared bus used by first generation linecards

C256 Gbps modules that are able to connect to a switching fabric 256 Gbps

last generation linecards able to connect to the 720 Gbps switching fabric that is mounted on sup 720 series supervisors.

To be noted all these numbers are doubled counting tx and rx twice.

so 160 Gbps capacity means 80 Ge ports full duplex at wire rate.

This is done by all switch builders and it is important to know.

Hope to help


Joseph W. Doherty Mon, 09/14/2009 - 09:00
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Fabric bandwidth should indicate the total capacity of moving bits between ports. 160-Gbps should mean, there's capacity to move 80 Gbps, duplex. How ports gain access to such bandwidth depends on the switch's architecture.

For a chassis switch, fabric bandwidth is often quoted for the whole chassis. Again, though, how it's allocated within the chassis depends on switch's architecture.

"As in chasis switch all cards are installed on same backplane ( like PC motherboard ). "

Depends on the switch's architecture. (Oh, and BTW, although PC cards might physically connect to the motherboard, such connections might be on different backplanes [or buses].)

I don't have a reference for a good tutorial or explanation for switch fabrics, but did give you an "taste" of switch architectures, here a link to a whitepaper on the 6500's: http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps708/prod_white_paper0900aecd80673385.html


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