[e2e] Wireless Networks. An Example: GPRS.

Detlef Bosau detlef.bosau at web.de
Wed Mar 13 10:52:45 PDT 2013

Just me again.

Am 12.03.2013 13:14, schrieb Martin Heusse:
> 1) no one knows the number of store and forward hops nor the latency 
> in advance so you have to guess (or create some kind of cross-layer 
> mechanism… Good luck with that…) The first hop that your TCP/IP stack 
> sees is the GGSN in the GPRS network, and there are many store and 
> forward nodes between them. 

I agree with you that we need to know "somehow", how many packets can be 
kept in flight.

However, how is this known in wireless networks? That's one interesting 

When the "only link" is a GPRS link (admittedly not only the air 
interface but the other necessary nodes as well) or some other wireless 
link technology,
how do you know the "path capacity"?

Up to now, I think we have a certain loss differentiation problem, so 
VJCC will fail here.

So, how do we handle this? Add 10 Ethernet links in advance and 10 
afterwards and solve the problem end 2 end?

That's the core of my question. A congestion control strategy which 
cannot successfully deal with a single link is not fixed by adding links 
in advance and links after "the problem". A correct e2e congestion 
control strategy will certainly work for each single link or link or 
switching node along the path!
Or don't you agree here?

Detlef Bosau
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