[e2e] Delays / service times / delivery times in wireless networks.
detlef.bosau at web.de
Fri Feb 23 03:03:06 PST 2007
David P. Reed wrote:
> Once the folks who ran IP networks over frame relay realized that you
> should never provision reliable delivery if you were running IP, this
> stopped happening.
> So the story is that GPRS can, if it tries to provide QoS in the form
> of never dropping a frame, screw up TCP.
> But this has nothing to do with mobility per se. It has to do with
> GPRS, just as the old problems had to do with Frame Relay, not with
> high speed data. The architecture of the GPRS network is too smart.
How smart is "too smart"?
And how much smartness is necessary?
Some authors note that the IP packet delivery time in mobile networks is
in fact a random variable, because the information rate in wireless
networs sometimes changes several times _within_ one packet. The reasons
are manifold and as a computer scientist, I have only a rough
understanding of some of the relevant issues here.
To my understanding, the basic question is: Which packet corrution rate
can be accepted by an IP network?
This is perhaps no fixed number but there is some tolerance in it.
However, I think we can agree that a packet corruption rate less or
equal to 10^-3 does not really cause grief. On the other hand, when the
rate of successful transmussions is less or equal to 10^-3, the network
is quite unlikely to be used.
So the truth is perhaps not out there but somewhere in between ;-)
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