<html>
<head>
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
</head>
<body bgcolor="#FFFFFF" text="#000000">
<div class="moz-cite-prefix">Am 13.12.2012 15:57, schrieb Jim
Gettys:<br>
</div>
<blockquote
cite="mid:CAGhGL2AFHw+5KkngML-aRymsCDtNfpesAWSL+f0bpKBgMzkJpg@mail.gmail.com"
type="cite">
<meta http-equiv="Context-Type" content="text/html;
charset=ISO-8859-1">
<br>
<div class="gmail_extra"><br>
<br>
<div class="gmail_quote">On Thu, Dec 13, 2012 at 6:15 AM,
Eggert, Lars <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:lars@netapp.com" target="_blank">lars@netapp.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote">
<div class="im">On Dec 12, 2012, at 16:38, Detlef Bosau <<a
moz-do-not-send="true" href="mailto:detlef.bosau@web.de">detlef.bosau@web.de</a>>
wrote:<br>
> My central question at the moment is: Do we have
stationary packet delivery times on mobile wireless links?<br>
<br>
</div>
</blockquote>
<div>Not sure what you mean by "stationary".</div>
<div><br>
</div>
<div>This crossed my radar screen:</div>
<div><br>
</div>
<div><a moz-do-not-send="true"
href="http://conferences.sigcomm.org/sigcomm/2012/paper/cellnet/p1.pdf">http://conferences.sigcomm.org/sigcomm/2012/paper/cellnet/p1.pdf</a></div>
</div>
</div>
</blockquote>
<br>
<br>
Thanks for the hint. This is not exactly what I had in mind, however
it is extremely closely related. I.e. at a very first glance, non
stationary delivery times can result in a buffer bloat phenomenon.<br>
<br>
To bring it to a simple point (Lachlan, please don't hurt me.....
;-)): The typically "serialization delay" which is typically used in
network simulators is simply wrong for mobile networks. It is SIMPLY
WRONG to use "constant rates" for mobile networks, <br>
<br>
- first because in mobile networks net data rates may change
(sometimes several times within the transport of one single IP
packet), for adaptation reasons,<br>
- second because mobile networks often employ opportunistic
scheduling algorithms which may cause a channel getting no service
for some period of time,<br>
- third because mobile networks typically employ some kind of
recovery layer with automatic retransmission.<br>
<br>
So the simple "serialization and delivery" of a packet of, say, 1024
bytes length in GPRS may last from 7 seconds to 375 seconds
according to the relevant ETSI standards. There may be other delays
than the mentioned ones and the issue is perhaps much more complex
than I said, however one must not, as in wired networks, take a net
data rate of, e.g., 10 MBit/s and 1024 byte and expect a
"serialization delay" and think the "serialization delay" were 891,2
microseconds.<br>
<br>
Actually, even the values taken from the standard are 0,95
quantiles. So the "serialization" delay may last much longer, it is
even possible that the packet is not delivered at all and hence
stays in the queue forever.<br>
<br>
<br>
<pre class="moz-signature" cols="72">--
------------------------------------------------------------------
Detlef Bosau
Galileistraße 30
70565 Stuttgart Tel.: +49 711 5208031
mobile: +49 172 6819937
skype: detlef.bosau
ICQ: 566129673
<a class="moz-txt-link-abbreviated" href="mailto:detlef.bosau@web.de">detlef.bosau@web.de</a> <a class="moz-txt-link-freetext" href="http://www.detlef-bosau.de">http://www.detlef-bosau.de</a>
------------------------------------------------------------------
</pre>
</body>
</html>