Cisco Catalyst 3750 QoS Configuration Examples is also a decent documentation, can be found on the following link. http://www.cisco.com/en/US/products/hw/switches/ps5023/products_tech_note09186a0080883f9e.shtml
On Mon, Jan 17, 2011 at 12:27 AM, Dan Letkeman <[email protected]> wrote: > 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/ > _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
