exit fast recovery data 14 was lost earlier

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Unformatted text preview: ossible signals, with different pros/cons –  We’ll look at classic TCP that uses packet loss as a signal Signal Example Protocol Pros / Cons Packet loss TCP NewReno Cubic TCP (Linux) Hard to get wrong Hear about congestion late Packet delay Compound TCP (Windows) Hear about congestion early Need to infer congestion Router indication TCPs with Explicit Congestion Notification Hear about congestion early Require router support 289 TCP Tahoe/Reno •  Avoid conges7on collapse without changing routers (or even receivers) •  Idea is to fix 7meouts and introduce a conges7on window (cwnd) over the sliding window to limit queues/loss •  TCP Tahoe/Reno implements AIMD by adap7ng cwnd using packet loss as the network feedback signal 295 41 11/4/13 TCP Tahoe/Reno (2) •  TCP behaviors we will study: –  ACK clocking –  Adap7ve 7meout (mean and variance) –  Slow- start –  Fast Retransmission –  Fast Recovery •  Together, they implement AIMD 296 Introduc7on to Computer Networks TCP Ack Clocking (§6.5.10) Computer Science & Engineering 42 11/4/13 Sliding Window ACK Clock •  Each in- order ACK advances the sliding window and lets a new segment enter the network –  ACKs “clock” data segments 20 19 18 17 16 15 14 13 12 11 Data Ack 1 2 3 4 5 6 7 8 9 10 301 Benefit of ACK Clocking •  Consider what happens when sender injects a burst of segments into the network Queue Fast link Slow (bokleneck) link Fast link 302 43 11/4/13 Benefit of ACK Clocking (2) •  Segments are buffered and spread out on slow link Segments “spread out” Fast link Slow (bokleneck) link Fast link 303 Benefit of ACK Clocking (3) •  ACKs maintain the spread back to the original...
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