[e2e] performance of BIC-TCP, High-Speed-TCP, H-TCP etc

[Douglas Leith]

For those interested in TCP for high-speed environments, and perhaps 
also people interested in TCP evaluation generally, I'd like to point 
you towards the results of a detailed experimental study which are now 
available at:

http://www.hamilton.ie/net/eval/ToNfinal.pdf

This study consistently compares Scalable-TCP, HS-TCP, BIC-TCP, FAST-TCP 
and H-TCP performance under a wide range of conditions including with 
mixes of long and short-lived flows.  This study has now been subject to 
peer review (to hopefully give it some legitimacy) and is due to appear 
in the Transactions on Networking.

The conclusions (see summary below) seem especially topical as BIC-TCP 
is currently widely deployed as the default algorithm in Linux.

Comments appreciated.  Our measurements are publicly available - on the 
web or drop me a line if you'd like a copy.

Summary:
In this paper we present experimental results evaluating the
performance of the Scalable-TCP, HS-TCP, BIC-TCP, FAST-TCP and
H-TCP proposals in a series of benchmark tests.

We find that many recent proposals perform surprisingly poorly in
even the most simple test, namely achieving fairness between two
competing flows in a dumbbell topology with the same round-trip
times and shared bottleneck link. Specifically, both Scalable-TCP
and FAST TCP exhibit very substantial unfairness in this test.

We also find that Scalable-TCP, HS-TCP and BIC-TCP induce significantly 
greater RTT unfairness between competing flows with different round-trip 
times.  The unfairness can be an order of magnitude greater than that 
with standard TCP and is such that flows with longer round-trip times
can be completely starved of bandwidth.

While the TCP proposals studied are all successful at improving
the link utilisation in a relatively static environment with
long-lived flows, in our tests many of the proposals exhibit poor
responsiveness to changing network conditions.  We observe that
Scalable-TCP, HS-TCP and BIC-TCP can all suffer from extremely
slow (>100s) convergence times following the startup of a new
flow. We also observe that while FAST-TCP flows typically converge
quickly initially, flows may later diverge again to create
significant and sustained unfairness.

--Doug

Hamilton Institute
www.hamilton.ie