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<div class="moz-cite-prefix">Am 27.12.2012 00:01, schrieb
<a class="moz-txt-link-abbreviated" href="mailto:dpreed@reed.com">dpreed@reed.com</a>:<br>
</div>
<blockquote cite="mid:1356562906.75320908@apps.rackspace.com"
type="cite">
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<p>In mobile networks (let's include wifi there) a packet is
either <br>
reliably delivered - in unpredictable time.<br>
Or it is unreliably delivered - that is possible in predictable
time.</p>
<p>Â </p>
<p>That is also true of wired networks. </p>
</blockquote>
<br>
<br>
Absolutely. However, in wired networks packet corruption is
(hopefully) that rare, that the "unreliably delivered" packets are
delivered "unreliably" with p_succ= 0.9999 or something similar.
(Simply spoken: Corruption loss is typically ignored.)<br>
<blockquote cite="mid:1356562906.75320908@apps.rackspace.com"
type="cite">
<p>It is the fundamental constraint of packet networking. At any
level, one can decide to choose either case. Rather than
"unpredictable", one should say "unbounded stochastic".</p>
<p>Â </p>
</blockquote>
<br>
E.g. in GPRS, the standard defines certain quantiles. E.g. for 1024
bytes, we have certain delay classes:<br>
          <br>
<pre>                mean                  0.95 quantil</pre>
<pre>
1.:Â Â Â Â Â Â Â Â Â Â Â Â < 2s < 7
2.: < 15s < 75s
3.: < 75s < 375s
</pre>
I don't now whether "mean" refers to "average value" or "median".<br>
<br>
Each class refers to some different sdu corruption probability. (I
don't have the values in mind, may be 10^-3, 10^-5, 10^-9, however
10^-9 will ever be implemented.... ;-))<br>
<br>
If you have a look at typical simulation systems, e.g. the NS-2,
wireless interfaces are assigned a certain "rate". Which implicitly
assumes a more or less stationary delay. Does that make sense?<br>
<br>
Particularly, as the extremely high latency 375 s most likely refers
to some "countless" repetition of packets (100 times, 1000
times....), which may indicate a situation where we should rather
choose a different interface or a different route if possible.<br>
<br>
<br>
<br>
<br>
<pre class="moz-signature" cols="72">--
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Detlef Bosau
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The nonsense that passes for knowledge around wireless networking,
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