Christian Konecny (VI/SEA) schrieb: > > Carl-Daniel wrote: >> That's strange. On my bridge with 4 network interfaces, >> the additional latency is always below 0.5 ms, even if >> I'm pushing 400 MBit/s through the machine and a kernel >> compile is running at 100% CPU. Network interfaces are >> PCIe GBit from Syskonnect, the machine is an Athlon64 >> at 2 GHz. Even if the clock speed is halved by powersave >> the additional latency will not go above 0.9 ms. >> Kernel is vanilla 2.6.11.x. > > Did you use certain specific compile options? Depends. I chose to use a slightly modified .config from SUSE 9.3 (attached). > I have changed now from (Knoppix) Debian to (Slax) > Slackware running now 2.6.12.2 and have exactly the > same on each machine. > top shows me a CPU usage less than 0.5%, load average > 0.1 while the bridge is handling roughly 64kBit/sec. > I can still measure a variable delta between packets > of 5ms-10ms. > How did you measure your latency values? (with bridge in between) linux:~ # ping -f -c 1000 192.168.0.1 PING 192.168.0.1 (192.168.0.1) 56(84) bytes of data. --- 192.168.0.1 ping statistics --- 1000 packets transmitted, 1000 received, 0% packet loss, time 963ms rtt min/avg/max/mdev = 0.642/0.914/2.487/0.277 ms, ipg/ewma 0.964/1.023 ms (same config without bridge in between) linux:~ # ping -f -c 1000 192.168.0.1 PING 192.168.0.1 (192.168.0.1) 56(84) bytes of data. --- 192.168.0.1 ping statistics --- 1000 packets transmitted, 1000 received, 0% packet loss, time 883ms rtt min/avg/max/mdev = 0.767/0.834/4.925/0.173 ms, ipg/ewma 0.884/0.814 ms > I am using 3 PCs, one is the Linux-Box acting as bridge > (brctl addbr br0; brctl addif br0 eth0; brctl addif br0 > eth1), the other 2 PCs are connected to either side of > the bridge, running ethereal. I'm using 2 PCs (one as bridge, one as local client) and a Cisco Pix (slow, insecure, unstable) as remote router (192.168.0.1). The measaurements were done from the local client. > In my case I have 2 Phone systems generating continous traffic. Each > system is sending out packets every 30ms. > If I compare the 2 traces I can see that after the bridge the timings > are different then before the bridge. It is very possible that a bridge changes the timing distribtion (but the drastic effect you're seeing shouldn't happen). > The difference is always in steps of 5ms. > so, on sending side is always 30ms difference between each packet > on receiving side - after the bridge - the delta is then 25,30,35, or 40ms. > > Is this really different in your setup? Since the remote side is not a linux box, my chances to measure the timing distribution are somewhat limited. Please try the flood ping I did above (ping -f -c 1000 re.mo.te.ip) and report your results. If you can see latencies above 2 ms something is definitely going wrong. Could be the nic, the nic settings (NAPI), the timing source or packet type (ICMP vs. IP). 1. Check ping 2a. If ping looks wrong -> try my .config and check again 2b. If ping looks OK -> try the phone while running (ping -f re.mo.te.ip) 3. Report back. Grüße aus Tübingen Carl-Daniel -- http://www.hailfinger.org/
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