[LARTC] Latency of Linux Bridge

[Christian Konecny (VI/SEA)]

Thank you very much for your feedback!



Carl-Daniel Hailfinger wrote:
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> 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
=========================

Same here. Ping delivers me the same values.
I also tried following
ping -f -c 1000 192.168.0.1 -i 0.03

this produces pretty the same traffic like the one I have from my telephony systems.
I did a sniffer-trace on that and could not see any deviations as big as 5ms.
Therefore I assume the bridge will handle ICMP easier/faster than normal UDP-traffic.

I also did another test with iperf (http://dast.nlanr.net/Projects/Iperf/) 
with similar values:

iperf -c 192.168.0.1 -u -len 90 -t 7200 20k

This produces UDP traffic with 90ms packets every 30ms.
Now I have again the deviations in steps of 5ms.

So, icmp might not be a good tool to measure jitter in this terms.

I am pretty sure you will have the same with iperf or any other method to produce UDP-traffic.





Carl-Daniel Hailfinger wrote:
=========================
It is very possible that a bridge changes the timing distribtion
(but the drastic effect you're seeing shouldn't happen).
=========================
I fully agree ;-)



thanks,
Christian

PS: What I am doing wrong?
Each mail from me is not put correctly into the corresponding position within the thread of the mailing list.
Have M$ Outlook here...