[c-nsp] 2960S drops/packet loss

[Joerg Mayer]

On Fri, Dec 23, 2011 at 07:45:36AM +1100, John Elliot wrote:
> Thanks - Fairly certain we are seeing actual drops (And we are seeing packet-loss across this link)

I'm convinced you do. As has been previously discussed on this list: 2960- and
3560-series have catastrophically small output buffers.
Just to give you my personal experience: Two video streams (average <10 Mbit/s
each) manage to drop packets on the same outgoing ports when both send their
I-frames simultanously. In this particular setup the tweak mentioned below
actually "fixed" the problem.

> Gi1/0/17 is mapped to asic 0/20
> 
> Gi1/0/17  17   17   17   0/20 1    17   17   local     Yes     Yes
> 
> Port-asic Port Drop Statistics - Summary
> ========================================
> 
>  Port 20 TxQueue Drop Stats: 308277833
> 
> And majority appear to be in Queue 1:
> 
> So hoping someone can suggest a few tweaks to reduce these drops(And also (more importantly!) the packet-loss)

Replace by "real" ethernet switching hardware.
As an alternative: *If* you have the drops on some "output" ports where various
"feeder" ports send their data, then change the feeder ports from 1000-full to
100-full. If you have a more symmetric setup, see my real advice to replace the
hardware.

Sorry to have no better answer for you.

ciao
      Jörg
-- 
Joerg Mayer                                           <jmayer at loplof.de>
We are stuck with technology when what we really want is just stuff that
works. Some say that should read Microsoft instead of technology.