From: Kate Everitt (kteveritt@yahoo.com)
Date: Tue Oct 19 2004 - 22:19:31 PDT
Congestion Control for High Bandwidth-Delay Product
Networks
Review: Katherine Everitt
This paper presented XCP, a new eXplicit Control
Protocol to replace TCP. The key aspects of XCP are
that it is more stable and efficient when bandwidth
and latency increases, and that it decouples fairness
and efficency.
The main advantage of XCP is that its parameters are
constants, and thus independent of things such as the
delay and capacity at the bottleneck. This makes it
easier to calibrate and more likely to work in a
variety of situations. It is faster at noticing
congestion too, as the implicit “packet loss” signal
takes a while to time out, and may also indicate a
packet loss instead of congestion. XCP is faster to
come back up to after a congestion signal, because it
has more speed. Because the fairness and efficiency
controllers are decoupled, it is easier to make a
change to one of them without affecting the other, and
you can have more specific controllers in any given
situation.
The analysis was very detailed, and it seems that XCP
is a better and more robust protocol than TCP.
However, to deploy it in practice would involve making
changes to routers, no easy task. Also, this will be
complicating the network and does not really fully
address the problem of Denial of Service attacks.
Overall this seemed a good solution to a problem that
is not-quite-here-yet, but if we see it, we’ll know
what to do.
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