X1 ack y1 time 173 5 11413 connec7on release

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Unformatted text preview: server) •  Each side probes the other with a fresh Ini7al Sequence Number (ISN) –  Sends on a SYNchronize segment –  Echo on an ACKnowledge segment •  Chosen to be robust even against delayed duplicates 172 Three- Way Handshake (2) •  Three steps: Ac7ve party (client) –  Client sends SYN(x) –  Server replies with SYN(y)ACK(x+1) –  Client replies with ACK(y+1) –  SYNs are retransmiked if lost •  Sequence and ack numbers carried on further segments 1 SYN (S SY Passive party (server) EQ=x) 2 ) K=x+1 =y, AC N (SEQ (SEQ 3 =x+1 , ACK = y+1) Time 173 5 11/4/13 Connec7on Release •  Orderly release by both par7es when done –  Delivers all pending data and “hangs up” –  Cleans up state in sender and receiver •  Key problem is to provide reliability while releasing –  TCP uses a “symmetric” close in which both sides shutdown independently 183 TCP Connec7on Release •  Two steps: Ac7ve party Passive party –  Ac7ve sends FIN(x), passive ACKs –  Passive sends FIN(y), ac7ve ACKs –  FINs are retransmiked if lost •  Each FIN/ACK closes one direc7on of data transfer 184 6 11/4/13 TCP Connec7on Release (2) •  Two steps: Ac7ve party –  Ac7ve sends FIN(x), ACKs –  Passive sends FIN(y), ACKs –  FINs are retransmiked if lost •  Each FIN/ACK closes one direc7on of data transfer Passive party FIN (SEQ=x 1 ) x+1) , ACK= (SEQ=y =x+1) y, ACK (SEQ= FIN 2 (SEQ=x+1 , ACK=y+ 1) 185 Introduc7on to Computer Networks Sliding Windows (§3.4, §6.5.8) Computer Science & Engineering 7 11/4/13 Sliding Window •  Generaliza7on of stop- and- wait –  Allows W packets to be outstanding –  Can send W packets per...
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This document was uploaded on 04/04/2014.

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