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Marketing Math or Cisco Math...

I’m trying to understand system architecture as it relates to backplane speeds and switching fabrics.

Some devices have switching fabrics while others don’t. Example 6500 can be installed with a SFM increasing the system throughput to 256 Gbps from 32 Gbps Shares Bus. First question…The Shared Bus is on the backplane of the switch and all cards have access to the bus. Does the SCP determine where the frames go or as the name states it’s a shared bus and all line cards see the data?

When a SFM is installed only certain cards can utilize the SFM. So does the SFM make switching decisions or does the SFM provide a larger 256 Gbps bus to the SCP??

All of this stemmed from product comparison. The Juniper M320 supports 320 half Duplex. The Cisco 7600, with sup720, supports an aggregate of 720 Gbps. Is the 720 half or full duplex?

A colleague of mind says that it’s 720 half duplex and 360 full duplex. And the M320 is 320Gbps half duplex and 160 Gbps Full Duplex. That threw me for a loop. I would think it would be the other way around. He goes on to refer this as marketing math or Cisco math. Can someone please explain?

Sorry so long. Thanks for reading.


Re: Marketing Math or Cisco Math...


The Sup720 supports 720Gbps of aggregate traffic, which means that it supports 360Gbps of full-duplex, with 360Gbps of receive and 360Gbps of transmit traffic, giving you an aggregate of 720Gbps.

The M320 supports an aggregate throughput of 320Gpbs, which means that is supports 160Gbps of full-duplex throughput.

Notice anything common here ? The full-duplex throughtput is always doubled to give you the aggregate throughput. Why ? The bigger the better, right ? That is marketing speak...

So your colleague us right (in marketing speak)... a full-duplex bandwidth of X will mean two half-duplex bandwidths of X, giving you a total of 2X half-duplex bandwidth.

Hope that helps - pls rate the post if it does.