We saw similar problem and we solve it by doing etherchannel on the output interface.
Nitzan On Wed, Oct 1, 2008 at 11:19, Gert Doering <[EMAIL PROTECTED]> wrote: > Hi, > > one of our switches is misbehaving, and I'm wondering whether this is a > configuration thing, or a hardware limitation. > > (It's not actually a QoS thing, but it's bordering on it) > > Setup: WS-C2960G-24TC-L, effectively only 4 ports active: > > This is where stuff comes in (UDP audio streaming servers): > > GigabitEthernet0/8 is up, line protocol is up (connected) > 5 minute input rate 26179000 bits/sec, 3819 packets/sec > 5 minute output rate 3492000 bits/sec, 3295 packets/sec > GigabitEthernet0/12 is up, line protocol is up (connected) > 5 minute input rate 334588000 bits/sec, 41069 packets/sec > 5 minute output rate 14453000 bits/sec, 26859 packets/sec > GigabitEthernet0/16 is up, line protocol is up (connected) > 5 minute input rate 27730000 bits/sec, 2940 packets/sec > 5 minute output rate 1507000 bits/sec, 1976 packets/sec > > And this is where it leaves the switch: > > GigabitEthernet0/10 is up, line protocol is up (connected) > 5 minute input rate 19432000 bits/sec, 32108 packets/sec > 5 minute output rate 380792000 bits/sec, 46406 packets/sec > > As you see, the ports are far from saturated, and even the load from all > "ingress" ports (380 Mbit + 27 Mbit + 26 Mbit) is far from the capacity > of the "egress" port (G0/10). > > But still... > > GigabitEthernet0/10 is up, line protocol is up (connected) > Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: > 8731686 > > ... and this is of course affecting the audio quality. > > (The output port goes to a Juniper SSG550 firewall, which has no problem > keeping up with the load to about 950 Mbits/s - and if only one ingress > port > is active on the switch, we can see much higher egress load without > noticeable > drops) > > > IOS version on the switch is 12.2(46)SE, but I had (25)SEE on it before > that, and observed the same symptoms (except that (25)SEE does not > display the output drops in the counters). > > Right now, "mls qos" is *deactivated*, because we actually don't want > QoS as in "drop specific packets" here - we want "move ahead all packets!". > > If I enable "mls qos", the packet drops go way up - which I read as "the > existing buffers, that are already not really huge, are split into 4 > smaller queues, and thus microbursts are causing much higher drops". > > > My theory is that the streaming servers are micro-bursting (send out > packets with full wire rate for 1/100s, and then do nothing for 99/100s), > and that the switch has too small buffers to join the 4 ingress ports > towards the egress ports. But I'm not sure how to validate that. > > > So, here comes the questions: > > - how much buffer space per port does the 2960G have? > > - how can I find out why the switch is dropping packets? > > - what L2 switches are other people using in environments with > continuous high load that has "microbursts"? > > - any other tricks that people are using to make servers more well-behaved > regarding packet sending rate? Like "shaping traffic on the servers" > (to distribute the packets more evenly along the time scale)? > > > We have other streaming customers, and they are directly connected to > 6408A or 6724 ports on 7600s, and not displaying anything unusual, at > even higher loads (multiple ingress ports running at >800 Mbit/s for > hours, egress via port-channels). So it's something with this 2960G... > > gert > -- > USENET is *not* the non-clickable part of WWW! > // > www.muc.de/~gert/ <http://www.muc.de/%7Egert/> > Gert Doering - Munich, Germany > [EMAIL PROTECTED] > fax: +49-89-35655025 > [EMAIL PROTECTED] > > _______________________________________________ > 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/
