[e2e] Delivery Times .... was Re: Bandwidth, was: Re: Free Internet & IPv6
detlef.bosau at web.de
Thu Dec 27 07:48:14 PST 2012
Am 27.12.2012 10:05, schrieb Detlef Bosau:
> E.g. in GPRS, the standard defines certain quantiles. E.g. for 1024
> bytes, we have certain delay classes:
> mean 0.95 quantil
> 1.: < 2s < 7
> 2.: < 15s < 75s
> 3.: < 75s < 375s
> I don't now whether "mean" refers to "average value" or "median".
Of course, there are reaons for these high latencies: As David noted,
these may result from a huge number of retransmissions.
And the difference between "mean" and the 0.95 quantil indicate a high
variance, thus an application which will exploit the available
"throughput", i.e. the "mean" latency, may require huge buffers - and
thus see huge round trip times.
Hence, the question is whether TCP as is and mobile networks are really
Obviously, it's a matter of fact that there is that TCP over mobile
networks is requested from the market. So the issue is to find a good
match, at least compromise, between expectation and reality here.
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