[c-nsp] Throughput Issues with Trunk Between Switches

[Tim Franklin]

> We have tried this across Cisco 3550's, 3560's, 3750's and 6509's.
> The controllers are not showing any kind of errors during the testing.
> That is what is confusing me.
> When testing with small packet sizes and approaching 98 -99% capacity
> on a 1 Gig link, that is when the errors appear. 
> We are talking about 64, 128, and 256 bit packet sizes. There are
> errors even at the larger packet sizes, but not as many due to the
> number of packets that can passed over the 1G link.

You've only got 1G between switches, but your frame size is increasing between the access port and the trunk port.

If you've got 1G of N-byte frames (1G/N frames per second) coming in to the access port, you can't send (1G/N)*(N+4) out of the trunk port, it's going to be > 1G.

Regards,
Tim.