Pipe sizes
Large pipes are problematic
- Timeouts when multiple losses occur
- SACK fixes this (plus timestamp, PAWS, etc.)
- The rtt-bias unfairness problem remains…
- How big an rtt before TCP is unusable?
Small pipes are the more pressing problem!
- Far too many timeouts
- 55% of all recovery in one traffic trace of a busy Web server (over 1.6 million connections)
- A solution: Newreno + Enhanced Recovery (ER)
- Follow packet conservation, sending new probe packets upon duplicate ACKs
- No timeouts unless congestion is “persistent”