Nick, Thanks for the detailed explanation.
The problem is I also see this on our gig switches as well. And only on ether channel's, not on a single interconnects. The traffic can be a such a minimum and I still see drops. I would like to tune the output buffers, but I'm not sure where to start. I know that I need to learn some more about qos, because we do have a voice network that is growing very fast. Do you know of some good documentation or books that I can start with? Dan. On Sun, Jan 16, 2011 at 9:14 AM, Nick Hilliard <[email protected]> wrote: > On 16/01/2011 02:30, Dan Letkeman wrote: >> >> Drops are happening even when its not under load. Has nothing to do >> with bandwidth. > > Dan, > > hypothetically on a 100Mb port, if you burst your output to 200 megs for 1 > second, then drop to zero traffic for 4 minutes 59 seconds, you will see: > > - 50% packet loss on the link > - a 5 minute throughput rate of 333000 bits per sec > > This is called a microburst. I.e. a burst of traffic which goes beyond the > capacity of the link, but which is too short to be measured accurately by > your 5 minute rolling average. Typically you'll see this on slower speed > lan links with bursty traffic, and it's why you're seeing relatively low > levels of traffic, but output drops on the interface. > > If you want to fix this problem, you have several potential workarounds: > > - increase your port speeds > - get a switch with bigger buffers > - tune the output buffers on your existing switch > - in your particular case, you could try fiddling with the etherchannel > hashing algorithm to see if it helps (it's unlikely to make the problem > disappear completely). > > Going back to your port channel > >> Port-channel2 is up, line protocol is up (connected) >> Hardware is EtherChannel, address is 001b.d59d.7199 (bia 001b.d59d.7199) >> MTU 1500 bytes, BW 200000 Kbit, DLY 100 usec, >> reliability 255/255, txload 24/255, rxload 2/255 >> Encapsulation ARPA, loopback not set >> Keepalive set (10 sec) >> Full-duplex, 100Mb/s, link type is auto, media type is unknown >> input flow-control is off, output flow-control is unsupported >> Members in this channel: Fa0/23 Fa0/24 > > Your problem is here ------> ^^^^^^^^^^^^^ > > You need to upgrade your switch to a gig capable device. You've outgrown > your existing equipment. > > Nick > _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
