[e2e] Are we doing sliding window in the Internet?

Detlef Bosau detlef.bosau at web.de
Mon Jan 8 23:50:42 PST 2007

Vadim Antonov wrote:
>> nt _does_ exist.
> Ah, you don't understand I said - namely that fairness enforcement should
> be done in the network, and not by the software in end hosts.
> Besides, TCP is not fair.  For example, long-RTT flows always lose to 
> short-RTT flows in non-stationary (i.e. real-life) scenarios.

Please read my comments on Dorgham Sisalem´s post yesterday.

That long-RTT flows lose to short-RTT flows results from the probing 
scheme used in TCP: When a flow increases its window one segment per 
round, a short RTT flow increases faster than a long RTT flow. However, 
we must use some probing scheme and this probing scheme should be 
adaptive to the path. And of course we have to take into account a 
flow´s RTT for a probing scheme because we must take into account how 
fast reactions of a network on probing will be visible.

WRT to leaving fairness to the network: I have no first hand experience 
with ABR. But I think, Dorgham told us about the experiences here yesterday.

To make a long story short: I think it´s already said in the Twelve 
Basic Network Truths but I think it´s generic:
There are always arbitrary much simple and wrong solutions to complex 
prolblems :-)

BTW: Just a pointer to literature: For a network based congestion 
control approach (hopefully I understood this work correctly) you should 
read the PhD thesis by Srinivasan Keshav. IIRC this is some really 
interesting work on ressource allocation in a complex network.


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