Re: Three states for a binary bit (was Re: TCP (and SCTP) sucks on high speed networks)

[Jon Crowcroft <J.Crowcroft@cs.ucl.ac.uk>]

In message <5.0.0.25.2.20001206093313.02db0eb0@mail.reed.com>, "David P. Reed" 
typed:

 >>At 09:09 AM 12/6/00 +0000, Jon Crowcroft wrote:
 >>>a pure end2end system that adapts to network conditions has a lag - at
 >>>best its around 1/4 RTT (asuming BECN for sender adaption and FECN for
 >>>receiver adaption)
 
 >>Quantifying lags in terms of RTT is wrong.  RTT's are being employed in 
 >>ambiquous ways (as they, sadly, often are) here.

yes, yr. right - i was being sloppy:
i meant the transmission and serialisation time (which are universal,
as you say "speed of light" time constants, of the scale of the system), and
excluding  the queueing time
 >>There's the "speed of light" RTT which uses prioritized packets that bypass 
 >>data packets, and the queue-driven RTT which uses packets that travel in 
 >>FIFO queues.  The latter are affected by congestion.
 >>
 >>One can do end-to-end adaptation just as fast as "inside the net" 
 >>adaptation with the same time constants, because the same information can 
 >>be available at the "speed of light".
 >>
 >>But it is just silly to tie the applications' hands behind their backs and 
 >>then say they can't implement overload management.
 >>

 cheers

   jon