 | | | UDP tuning to reduce packet discards? | UDP tuning to reduce packet discards? 2005-01-31 - By Larry Fahnoe
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Hello,
Red Hat Enterprise Linux ES release 3 (Taroon Update 4)
Compaq DL380 w/dual 3GHz Xeon & 3GB
I've got a system that I'm using to for network monitoring, gathering
mrtg (snmp) data for several hundred interfaces and flow-capture
(netflow) for a couple of cisco routers. I'm seeing a fair number of
discarded packets and a corresponding number of UDP receive errors.
The system generally runs with a light load (<1) so I'm not seeing
that there is a CPU contention problem. Interfaces are locked at
100/full and do not show errors. flow-capture normally does some
compression of data that it receives, and I have disabled that to see
if it improves the situation, however I am still seeing dropped
packets via netstat. Interestingly enough, flow-capture has the
ability to report the number of flows that have been lost, but it
reports none being lost regardless of compression settings.
After some digging this morning I don't see any tunable parameters
that might apply here, but I'm hoping I'm missing something. Is there
any way to tune UDP performance (buffers, etc.)?
--Larry
# uptime
10:44:53 up 10 days, 2:21, 4 users, load average: 0.07, 0.42, 0.56
# netstat -s --raw --udp
Ip:
22909625 total packets received
0 forwarded
161163 incoming packets discarded <<<<<<<<<<<
22693330 incoming packets delivered
23626667 requests sent out
Icmp:
18695 ICMP messages received
0 input ICMP message failed.
ICMP input histogram:
destination unreachable: 12030
timeout in transit: 1297
echo requests: 4468
echo replies: 900
661766 ICMP messages sent
0 ICMP messages failed
ICMP output histogram:
destination unreachable: 657298
echo replies: 4468
Udp:
13245753 packets received
657298 packets to unknown port received.
161229 packet receive errors <<<<<<<<<<<
12296835 packets sent
eth0 Link encap:Ethernet HWaddr 00:0E:7F:EF:26:B5
inet addr:172.30.12.130 Bcast:172.30.12.255
Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:2461252 errors:0 dropped:0 overruns:0 frame:0
TX packets:1180004 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:1814273003 (1730.2 Mb) TX bytes:400737580 (382.1
Mb)
Interrupt:11
eth1 Link encap:Ethernet HWaddr 00:0E:7F:EF:26:B4
inet addr:172.30.13.130 Bcast:172.30.13.255
Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:17399126 errors:0 dropped:0 overruns:0 frame:0
TX packets:15101759 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:462047228 (440.6 Mb) TX bytes:1793024171 (1709.9
Mb)
Interrupt:15
--
Larry Fahnoe, Fahnoe Technology Consulting, fahnoe@(protected)
952/925-0744 Minneapolis, Minnesota www.FahnoeTech.com
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