[e2e] Why Buffering?

[Lachlan Andrew]

2009/6/21 Detlef Bosau <detlef.bosau at web.de>:
> David P. Reed wrote:
>>
>> Dave - This is variously known as Little's Theorem or Little's Lemma.
>
> Little's Theorem can be easily applied in wired networks where a link's
> capacity is easily expressed as "latency throghput product".
>
> The situation becomes a bit more complicated in wireless networks,
> particularly WWAN, where the preconditions for Little's Theorem may not
> hold, particularly the service time may not be stationary or stable.

Little's law (N = T lambda) holds in basically all scenarios.  It
doesn't rely on stationarity.  It refers to long-run averages, which
wash out all of the fluctuations.  If the service time were "not
stable" in the sense of tending to infinity as time progresses, then
it would not apply simply (we'd have infinite T, and either infinite N
or zero lambda), but that is not the case in WWANs.

If your point is that Little's law doesn't tell us anything about
short-term behaviour, then that is certainly true.  The only
difference between WWANs and wired networks is what we can consider to
be "short-term".

(If your point is that having the knee depends on more than Little's
law, then that is also true...)

Cheers,
Lachlan

-- 
Lachlan Andrew  Centre for Advanced Internet Architectures (CAIA)
Swinburne University of Technology, Melbourne, Australia
<http://caia.swin.edu.au/cv/landrew> <http://netlab.caltech.edu/lachlan>
Ph +61 3 9214 4837