> Of course, by increasing the MTU, you increase the RTT in the case
> of low rate (time needed to transmit the packet) or BoD
> (ressources required to transmit the packet). Thus you have to
> adapt your socket buffer size (and thus your max window) to the
> BDP with the "real RTT", and not only the link delay.
I *think* I disagree, but I am not completely sure what you're
saying... Your buffer sizes need to be about 1*BDP of the unloaded
path. If you use a higher delay that the propagation delay then you
are building a persistent queue somewhere. Basically, the BDP of
the unloaded network is the number of bits that will "fit" into the
network at one time. So, if your window is bigger than this you are
pushing more bits than the network itself is able to handle over the
path. The bits either have to go into queues or in the bit-bucket.
(You might need to make a small change for the transmission time of
a packet ona slow link. I'd have to think about that some more.
But, in general you do not want to track the "real" RTT to determine
how big your socket buffers should be.)
allman
--- http://roland.grc.nasa.gov/~mallman/
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