[c-nsp] can't be -- output discards on 6500 gig-e

[Edward Henigin]

Hello,

I've got a 6509/sup720 that's having output discards on a gigabit ethernet
interface at peak time.  No biggie, you say, you're running the line
too hot.  But what's "too hot?"  We're seeing the discards when the
interface is doing 500Mbps on a 1 minute average.  I do not believe at
all that we should be getting output discards at that traffic level.

The card is a WS-X6416-GBIC.  It has 10 ports enabled.  We constantly
saw discards on the port at a rate of 40 to 70 packets/sec over a 3
hour period.  During the same 3 hour period, the port was doing 450Mbps
to 650Mbps, 40kpps - 55kpps, on a 5 minute average.

We opened a case with TAC and all they say is "you're running out of
output buffers."  I'm sorry, but that's not helpful at all.  This behavior
is unacceptable to me.  At 500Mbps, I should NOT be discarding packets,
even at that low rate.

Send flowcontrol is on, receive flowcontrol is off.  By my reading of
http://tinyurl.com/6omgc, that means that we will not process incoming
pause packets, and we should not be pausing our output to the other side.
So I don't believe that flowcontrol has anything to do with it.

Anyone else have any insight?

Thanks,

Ed