[e2e] TCP to exhibit MTU unfairness?

Detlef Bosau detlef.bosau at web.de
Tue Nov 20 02:34:14 PST 2007

Tze-Ven Poh wrote:
> If a few users are on a parking-lot type of network and are all paying 
> the same (monetarily) for the access service, is it fair for the 
> fellow who has to go through multiple congestion links to get lower rate?
> [just a question]
And it´s an interesting question, especially for wireless networks.

The question is: "What is fairness?"

Apparently, this word has at least ten times as much possible meanings 
as it has possible spelling errors.

The system model used in the congavoid paper focuses a very special 
situation: Comparable, if not identical, paths and a common bottleneck. 
And the goal was to share the common ressources equally.

If we consider a HSDPA cell, it is necessary to get a common sense which 
is the shared ressource and what fairness should mean in this context. 
To make a very long story very short here, the literature up to know 
focusses at "throughput fairness" here and simply does not take into 
accout i) ressource fairness and ii) (with one exception, which I´m yet 
to understand) asymmetric fading.
Where "asymmetric fading" itself indicates, that in wireless networks 
different terminals in one common cell may well face extremely different 
network conditions. An issue, you´ll never see in wirelined networks.

So, "what is fairness"?

Didn´t Pontius Pilatus raise the question: "What is truth?"

However, this discussion is indeed beyond this little discussion about 
MTU sizes :-)

But with special respect to wireless networks, I think the monetary 
aspect _is_ important. And particularly in wireless networks, customers 
pay mainly for wireless ressources (the wireline costs can be neglected 
in most cases) and therefore, it is extremely important to consider 
which ressources are given to whom and under which circumstances.


Detlef Bosau                          Mail:  detlef.bosau at web.de
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