10 - Introduction TCP Congestion Control TCP Fairness TCP...

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Introduction TCP Congestion Control TCP Fairness TCP Versions Take-Home Points Congestion Control Principles and TCP Algorithms Daniel Zappala Brigham Young University Computer Science Department Congestion Control Daniel Zappala 1/24
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Introduction TCP Congestion Control TCP Fairness TCP Versions Take-Home Points 1 Introduction Principles Congestion Collapse Approaches 2 TCP Congestion Control Mechanisms Visualizing 3 TCP Fairness Fairness Unfairness 4 TCP Versions Old New The Future 5 Take-Home Points Congestion Control Daniel Zappala 2/24
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Introduction TCP Congestion Control TCP Fairness TCP Versions Take-Home Points Question of the Day How do you send as fast as possible, without overwhelming the network? Challenges the fastest speed you can send changes all the time, due to many connections stopping and starting all the time you must have a stable solution you must provide fairness among different connections Congestion Control Daniel Zappala 3/24
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Introduction TCP Congestion Control TCP Fairness TCP Versions Take-Home Points Definition congestion : hosts sending data at a rate that exceeds network capacity effects delay packet loss Congestion Control Daniel Zappala 4/24
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Introduction TCP Congestion Control TCP Fairness TCP Versions Take-Home Points Infinite Buffering infinite buffering, no retransmission exponential arrival rate, characterized by an average median < average delay grows as arrival rate grows each link (and path) has a maximum achievable throughput Congestion Control Daniel Zappala 5/24
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Introduction TCP Congestion Control TCP Fairness TCP Versions Take-Home Points Finite Buffering finite buffering, retransmission λ 0 in = original rate plus retransmissions (a) perfect sender, no loss, λ in = λ 0 in = λ out (b) perfect retransmission, λ 0 in > λ out illustrates cost of congestion - for equal amount of work, less throughput (c) imperfect retransmission illustrates cost of unneeded retransmissions Congestion Control Daniel Zappala 6/24
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Introduction TCP Congestion Control TCP Fairness TCP Versions Take-Home Points Four Senders finite buffering multihop paths timeouts and retransmissions what happens as λ 0 in increases? Congestion Control Daniel Zappala 7/24
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TCP Congestion Control TCP Fairness TCP Versions Take-Home Points Congestion Collapse congestion collapse : as offered load increases, throughput suddenly drops to zero when a packet is dropped, the capacity used at early routers is wasted October 1986: this happened on the Internet! Van Jacobson and Michael J. Karels, Congestion Avoidance
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This note was uploaded on 10/18/2011 for the course CS 460 taught by Professor Staff during the Spring '05 term at BYU.

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10 - Introduction TCP Congestion Control TCP Fairness TCP...

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