Fabric-enabled modules in 6500 switches

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Oct 17th, 2009
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What does it mean "fabric-enabled" in 6500 switches and how much

difference is it between a normal module and a fabric-enabled module

in terms of performance?

waitong your replies



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Giuseppe Larosa Sat, 10/17/2009 - 12:39
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Hello Mohamed,

the C6500 architecture white paper is a very good document


in the C6500 coexist different types of forwarding plane facilities:

the older shared bus

the newer 256 GBps Exor 720 Gbps switching fabric

a fabric-enabled linecard can connect to a switching fabric.

CEF720 capable linecards can connect to 720 Gbps switching fabric that is present on Sup720 series supervisors.

older SFM modules provide a 256 Gbps switching fabric.

A shared bus is a bus that is only one communication can used it at the same time: if linecard x sends a frame to linecard y at the exact time t0 no other linecard can use the shared bus.

A switching matrix or fabric can be non blocking that is it allows for concurrent communcations between different linecards pairs.

An old linecard has a 8 Gbps connection to the shared bus.

A new linecard can have two 20 Gbps each connections to the switching fabric.

Hope to help


Joseph W. Doherty Sat, 10/17/2009 - 16:23
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Giuseppe's reference provides many details, but what a switch "fabric" normally provides is some type of cross bar architecuture that allows multiple points within the architecuture to communicate without sharing bandwidth. For example, port 1 can communicate with port 3, at full rate, while ports 2 and 4 do likewise (NB: fabric isn't always per port).

Within the 6500 architecture, many of the fabric capable cards support local forwarding decision making (with a DFC module) without involving the main chassis supervisor.

The two forging features support a very high aggregate processing and forwarding capacity compared to a 6500 using just "classic" line cards.

To contrast performance, a sup720 supports 15 or 30 Mpps and the shared classic bus 32 Gbps. The sup720 also provides a 720 Gbps fabric. CEF720 line cards, that support a DFC, the DFC supports 48 Mpps (this per each such card - about 400 Mpps for chassis).


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