[e2e] FTCP algorithm

Dohy HONG Dohy.Hong at ens.fr
Fri Apr 26 05:52:50 PDT 2002

Hi all,

I would like to open discussions about the ideas of
FTCP algorithm presented in:

This algorithm propose a simple modification of
TCP algorithm to improve the performance in a way
which is 'socially better'.
And it seems that there are 2 interesting properties
in using FTCP (F for fluid):
One is that it improve the End-to-End performance for
its user.
The second is that it encourages others to also use
this algorithm and become 'socially better'.

The basic idea is based on the remark that the
packet burstiness inside each RTT is not good:
especially with Slow Start and long RTTs.
If you have CWND=10 with RTT~1 second, it is better
to send 1 packet every 100 ms that to send a burst
of 10 packets.

What is your gain? I did some simple test modifying
the linux kernel and doing FTP and HTTP
(I also did some simple NS simulation which is described
in the draft).
My feeling was that you could gain about 0-50%
depending on RTT, congestion state etc. It would be
nice if other people could check this
independently. I would be more than happy to help
anyone who would like to do kernel modification 
(or for ns-2) for FTCP and get any feedback. 

What is the cost? Well, I think FTCP idea is more
efficient with a good timer granularity.
Timer is needed by the fact that you need to be
patient before sending packets after ACKs reception
(roughly speaking: try to send 1 packet every
A good point is also that this idea could be
implemented at the source or/and the destination level.

I naively hope that FTCP could become useful to
people in practice.

All comments, criticisms (even blames) are very

Projet TREC (Théorie des Réseaux Et Communications)

Département Informatique       
45 rue d'Ulm, 75230 PARIS CEDEX 05,  FRANCE    
Tel : 33 (1) 4432 2112, Fax : 33 (1) 4432 2151
Email : Dohy.Hong at ens.fr

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