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

[L.Wood@surrey.ac.uk]

Paul Francis wrote on Fri 2006-09-22 21:09

> Any reason XCP not included in this?

because XCP has morphed so many times no-one knows what it is anymore.

XCP is no longer a clearly-defined algorithm -- it's now a brand name.

L.

<http://www.ee.surrey.ac.uk/Personal/L.Wood/><L.Wood at surrey.ac.uk>

-----Original Message-----
From: end2end-interest-bounces at postel.org
[mailto:end2end-interest-bounces at postel.org] On Behalf Of Douglas Leith
Sent: Friday, September 22, 2006 10:22 AM
To: end2end-interest at postel.org
Subject: [e2e] performance of BIC-TCP, High-Speed-TCP, H-TCP etc

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




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