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PCP Design


Table 2: A Summary of PCP Mechanisms
Mechanism Description Goal Section
probes

Senders use short transmission bursts with limited payload to ``prove'' the existence of available bandwidth, while minimizing any long term effects of failed tests.

low loss Section 3.1
direct jump

Given a successful test, senders increase their base rate to the rate that test.

min response time Section 3.1
probabilistic accept

Accept tests taking into account the variance observed in the available bandwidth measurements.

fairness Section 3.1
rate compensation

When existing senders detect increasing queueing, they reduce their rates to drain the queue.

low loss,
low queues
Section 3.2
periodic probes

Senders periodically issue new probes to try to acquire additional bandwidth.

work-conserving Section 3.3
binary search

Senders use binary search to allocate the available bandwidth.

min response time,
work conserving
Section 3.3


exponential backoff



Senders adjust the frequency of tests to avoid test collisions and failures.

stability Section 3.3
history

Senders use heuristics to choose the initial probe rate.

min response time Section 3.4
tit for tat

Reduce speed of rate compensation if past compensation was ineffective.

TCP compatibility Section 3.5


In this section, we sketch the various elements of the PCP design. Table 2 provides a road map. For this discussion, we assume that PCP is used by all endpoints in the system to manage network resources; we defer to the end of this section a discussion of how to make PCP backwardly compatible with TCP end hosts. PCP represents a clean-slate redesign to endpoint congestion control; we do however retain the TCP mechanisms for connection management and flow control.



Subsections
next up previous
Next: Emulating Request-and-Set Up: PCP: Efficient Endpoint Congestion Previous: Design Goals
Arvind Krishnamurthy 2006-04-06