Re: icmp latency question

Linux Advanced Routing and Traffic Control

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the sew wrote:
> Our company's main line is quite busy the whole day and my shaping is
> working perfect, however even if I give icmp priority the pings still
> jump around quite a bit.
> 
> We do have a backup line which hardly get used only if the main line
> drops. I've set ip rule to route all icmp through that and now the
> pings are perfect.
> 
> Will this make a difference for the game players etc, with this low
> ping? or does the lagg on the game get effected by the throughput?

Sorry, I don't want to offend you, but your mail has been the cause for
the first good laugh of the day.

To get good results for online gaming, the roundtrip time of the packets
to and from the game servers needs to be good, and it should be fairly
constant, without sudden increases in the "lag time". To test this RTT,
most people use ping, as ICMP echo requests/replies are the perfect tool
for measuring this.

What you did was not to improve the RTT of the packets in the data
stream to and from game servers, but to falsify the results of RTT tests
done with ICMP. Now your measurements look perfect, without any change
to the real lag your gamers will experience.

You should not take "you need a good ping for gaming" literally. Really,
games do *not* use ICMP to connect to the servers. ;o)

I begin to doubt the wisdom of including rules for ICMP priorisation in
the many tc examples out there. Really, it does not make sense to send
out the packets used to test the average and best/worst case RTT of a
network as fast as the link allows at the cost of letting other traffic
wait, because then the result of a ping will have nothing to do with
what the sender of that ping wanted to know.

Just my € 0.02,
		Sebi

-- 
Sebastian Bork <sebi@xxxxxxxx>         ("`-''-/").___..--''"`-._
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