Subject: XCP, a paper of interest to tcpsat

From: Aaron Falk <[email-masked]>
Date: Thu, 8 Aug 2002 08:51:46 -0700

Hey folks-

This SIGCOMM 2002 paper may be of interest to those of you looking at
TCP performance over satellite.

--aaron

=====================

Congestion Control for High Bandwidth-Delay Product Networks. Dina
Katabi (MIT), Mark Handley (ICSI), Charlie Rohrs (Tellabs)

Abstract 

Theory and experiments show that as the per-flow product of bandwidth
and latency increases, TCP becomes inefficient and prone to
instability, regardless of the queuing scheme. This failing becomes
increasingly important as the Internet evolves to incorporate very
high-bandwidth optical links and more large-delay satellite links.

To address this problem, we develop a novel approach to Internet
congestion control that outperforms TCP in conventional environments,
and remains efficient, fair, scalable, and stable as the
bandwidth-delay product increases. This new eXplicit Control Protocol,
XCP, generalizes the Explicit Congestion Notification proposal
(ECN). In addition, XCP introduces the new concept of decoupling
utilization control from fairness control. This allows a more flexible
and analytically tractable protocol design and opens new avenues for
service differentiation.

Using a control theory framework, we model XCP and demonstrate it is
stable and efficient regardless of the link capacity, the round trip
delay, and the number of sources. Extensive packet-level simulations
show that XCP outperforms TCP in both conventional and high
bandwidth-delay environments. Further, XCP achieves fair bandwidth
allocation, high utilization, small standing queue size, and near-zero
packet drops, with both steady and highly varying
traffic. Additionally, the new protocol does not maintain any per-flow
state in routers and requires few CPU cycles per packet, which makes
it implementable in high-speed routers.

http://www.acm.org/sigcomm/sigcomm2002/papers/xcp.pdf