Switching Fabric & Switching Capacity

[Telnet-1-2]

i cannot understand difference between  Switching Fabric & Switching Capacity  ?

For example  when we say  :

300 Gbps (full duplex) per slot fabric capacity

The passive backplane design  capacity of up to 5  Tbps

what is difference between both ?

[Steve Fuller]

Hi,

The per slot capacity is simply that. The amount of capacity that the total ports on an I/O module in any single slot have for sending and receiving traffic to and from the switch fabric.

The total fabric capacity of a platform is usually some number that's calculated based on the per slot capacity * the number of slots in the chassis * two (for full duplex).

I've (hopefully) explained similar for the Nexus 7000 series switches in the post Nexus 7K Fabric Modules Bandwidth Capacity.

What platform are you referring to here with 300 Gbit/s per slot fabric capacity and 5 Tbit/s "passive backplane" or are these simply hypothetical numbers?

Regards

[Telnet-1-2]

Thansk , it is Just example numbers .

and what is difference in function between BackPlane & Switch Fabric  ?  both Switch traffic bwteen I/O Cards ?

Also why is switch fabric word is heared with Modular switches only ? for example for any fixed port switch we hear about switching Capacity only , no words about Switching Fabric ?

[Telnet-1-2]

Thansk , it is Just example numbers .

and what is difference in function between BackPlane & Switch Fabric  ?  both Switch traffic bwteen I/O Cards ?

Also why is switch fabric word is heared with Modular switches only ? for example for any fixed port switch we hear about switching Capacity only , no words about Switching Fabric ?

[InayathUlla Sharieff]

Hi,

Defination of Backplane bandwidth is the available bandwidth between the device's ports in the switch,internal backplanes or fabric bandwidths provide the bandwidth between ports within the same device, and can provide more or less or even the exact amount of bandwidth between the device's ports

Backplane bandwidth is a measure of the bandwidth of the internal architecture of the switch. The term is thrown around pretty loosely to refer to anything internal to the switch that doesn't refer directly to the packet forwarding rate of the forwarding engine.

The Backplane speed depends on the type of switch. (See Cisco Datasheet for more info)

A switching fabric is the combination of hardware and software that  moves data coming in to a network node out by the correct port (door) to  the next node in the network. A switching fabric includes the switching  units in a node, the integrated circuits that they contain, and the  programming that allows switching paths to be controlled. The switching  fabric is independent of the bus technology and infrastructure used to  move data between nodes and also separate from the router.

Switch  backplane speed is generally referred to as the aggregate bandwidth  available for switching across the chassis.

The Switch Fabric Module is what creates a dedicated connection between fabric-enabled modules and provides uninterrupted transmission of frames between these modules For example of Catalyst 6500, the switch faric is integrated in to s supervisor 720 engine and the switch fabric provides a direct connection between fabric-enabled modules provided by the Switch Fabric Module, fabric-enabled modules also have a direct connection to the 32-Gbps forwarding bus.

This URL will provide you indepth info about the C6500 switch fabric and you will have better understanding if you invest to time to read it..

http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps708/prod_white_paper0900aecd80673385.html

HTH

Regards

Inayath

*Plz dont forget to rate the usefull posts.