[Simgrid-user] Ordering of flows
kurt.vanmechelen at ua.ac.be
Tue Jul 1 11:51:24 CEST 2008
First of all thanks for the prompt feedback on GTNetS and the action delays.
We will keep the model in which we call back to SURF on each reported delay.
I will retry the GTNetS compilation this week and let you know if everything
I have a new question though. As our tests show, there is no flow "ordering"
in SURF. Suppose we have two hosts A and B, and A starts two communication
flows X and Y to B. Flow X is started at time U and flow Y at time V with U <
V. Now it appears that Y can finish before X, i.e. there is no (packet/flow)
ordering to ensure that X finishes before Y.
If I am not mistaken the TCP protocol prevents such reorderings from happening
by using sequence numbers. I also know that SURF is not supposed to do packet
I was wondering however whether you came across this issue before and how you
deal with this in message-based programs (i.e. programs that used your MPI
layer for example). In such programs it is important for this ordering to be
correct in order to assure a semantically sound execution of an RPC based
It is certainly an option for us to attach sequence numbers to our flows and
do the correct reordering ourselves (although this will require some more
Thanks a lot in advance for the info.
Dept. of Mathematics and Computer Sciences
Group CoMP (Computational Modelling and Programming)
University of Antwerp
2020 Antwerpen, Belgium
Phone : 03/265 3477
Mail : kurt.vanmechelen at ua.ac.be
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