L35 - TCP connection management SYN, FIN flags - start or...

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TCP connection management SYN, FIN flags - start or end of connection. SYN segment includes a starting send sequence number, usually selected at random. Start - three-way handshake. A could send the first piece of data with the ACK = y+1 segment.
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States in TCP connection management. Show Figs. 6-32, 6.33
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Window management Show Fig. 6.34
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TCP congestion control Rules were established for a source to decide how many packets it can send into the network without causing congestion. Idea is to use the round trip time for an ACK to control the window size. Ordinarily, an ACK is returned for each packet. A long round trip time to return an ACK suggests congestion. The parameter used is called the Congestion Window.
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The Congestion Window is £ the TCP advertised window. Reduce when congestion rises, increase when congestion level falls. TCP uses a strange way to control the congestion window size. The main impetus to a reaction with the congestion window is the occurrence of a timeout. A timeout value is set based on recent round trip time (RTT) measurements. If a timeout does not occur, the congestion window continues to rise until it reaches the advertised window.
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The assumptions are: 1) Timeouts are primarily due to lost packets, and 2) The loss is almost always due to packet dropping due to buffers filling from congestion. Loss due to bit errors are assumed negligible. Obviously, a noisy wireless link would destroy the value of these assumptions.
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“SLOW” START When starting or restarting, the congestion window is set at 1 segment.
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This note was uploaded on 09/23/2009 for the course CMPEN 362 taught by Professor Johnmetzner during the Spring '09 term at Penn State.

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L35 - TCP connection management SYN, FIN flags - start or...

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