James Ventre did a
bunch of research
uncovering some unpublished info on which ASICs talk to which ports.
The original link for his work is:
Taken with attribution but without permission.
The Cisco 2960G first ship was May 2006.
End-to-End Network QoS Design contains a description of the output queue
strategy for the 3750G that probably applies to the 2960G as well.
A unique feature of the Catalyst 3750 is that it supports flexible buffer
allocations to hardware queues, which may be dynamically loaned or borrowed
against (as needed). Specifically, each queue can lend part of its buffering
capacity, unless a specified minimum reserve threshold has been reached.
In addition, each queue may borrow up to four times its capacity from
a common pool of buffers (which are not allocated to any specific queue)
should these be available for use. The recommended buffer allocations for
queues 1 through 4 are 20 percent, 30 percent, 35 percent and 15 percent,
respectively. Correspondingly, the recommended parameters for reserve thresholds
and maximum (overload) thresholds are 100 percent and 400 percent, respectively.
For the priority queue, all thresholds should be set to 100 percent.
What the book does not say is how many packets or how much memory
is in the buffer pool. So, I asked.