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

Douglas Leith doug.leith at nuim.ie
Fri Sep 22 13:29:27 PDT 2006


Inevitably, these tests are a snapshot of sorts and things can move on 
while things get written up and the review process takes place.  Its not 
great, but seems hard to avoid.  The BIC folks for example have also 
developed Cubic that may address some of the issues flagged up, but this 
was post our tests and so isn't included.  I think the lesson here is 
that tests really need to be ongoing as protocols develop.  That said, 
XCP is perhaps at a different stage of development from other algorithms 
we've studied (all of which are possible candidates for rollout in the 
immediate future) as it seems to require router changes as well as 
end-host changes, and to my knowledge XCP support in production routers 
is not available yet.  I'm all for including it in future tests however.


Paul Francis wrote:
> Any reason XCP not included in this?
> PF
> -----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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