Hi-
Seeking to understand that status of the TCP fairness issue. Here are my
data points:
- TCP thoughput is a function of packet size, RTT, loss probability and RTO
as shown in the "Modeling TCP Throughput ..." paper by Padhye, et al from
Sigcomm '98.
- TCP may be biased against connections with long RTTs because the additive
increase time is roughly one segment per RTT. Connections with longer RTTs
take longer to ramp up and while this is happening those with smaller RTTs
can acquire available bandwidth. TCP constant rate algorithm as suggested
by Floyd and later Henderson, et al paper could overcome this limitation by
"equalizing" the rate by which senders with different RTTs increase their
sending rates during congestion avoidance. Not implemented.
- New techniques (larger initial windows, limited transmit) can help the
performance of small flows.
Anything else to look at? What about TCP and Diffserv? It was suggested by
recent Yeom and Reddy paper that it may be difficult to achieve
"contracted" TCP throughputs for higher rates and that those with smaller
rates would fare better.
My apologies if this is not relevant for the mailing list but I was
thinking that sat links can encompass the entire spectrum of
characteristics that impact TCP throughput.
Thanks ...
Chris Metz
Lead IP Architect
Solutions Integration
Service Provider Line of Business
Cisco Systems
email: [email protected]
offic phone: 408-525-3275
home office: 914-241-0423
pager: 800-365-4578
Internal URL: http://wwwin-people.cisco.com/chmetz/chmetz.htm
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