Lecture10 - 1 Thursday, May 1 Lab#2 Scores are posted Pick...

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Unformatted text preview: 1 Thursday, May 1 Lab#2 Scores are posted Pick up Homework #2 Due now Questions? Hope you made a copy for yourself Lab #3 Report is due tomorrow before midnight TAs have office hours today/tomorrow Program #1 Due Friday, May 9 Evaluation criteria are posted 2 Todays topics More Transmission Control Protocol (TCP) Connection, handshake Flow control Congestion control 3 TCP segment structure source port # dest port # 32 bits application data (variable length) sequence number acknowledgement number Receive window Urg data pnter checksum F S R P A U head len not used Options (variable length, padded to 32 bits) URG: urgent data (generally not used) ACK: ACK # valid PSH: push data now (generally not used) RST, SYN, FIN: connection estab (setup, teardown commands) # bytes rcvr willing to accept counting by bytes of data (not segments!) Internet checksum (as in UDP) 4 TCP header Source Port (16 bits): Identifies source user process Destination Port (16 bits): Identifies destination process Sequence Number (32 bits): Sequence number of the first byte in the segment. If SYN is present, this is the initial sequence number (ISN) and the first data byte is ISN+1. Ack number (32 bits): Next byte expected Header Length (4 bits): Number of 32-bit words in the header Reserved (6 bits) Code bits (6 bits): Urgent pointer field significant, ack field significant, push function, reset the connection, synchronize the sequence numbers, no more data from sender Window (16 bits): Will accept [Ack] to [Ack]+[window] Checksum (16 bits): covers the segment plus a pseudo-header. Includes the following fields from IP header: source and dest adr, protocol, segment length. Protects from IP misdelivery. Urgent pointer (16 bits): Points to the byte following urgent data. Lets receiver know how much urgent data is coming. Options (variable) MSS, etc. Must be padded to 32 bits 5 TCP Connection Establishment Three way handshake: Step 1: client host sends TCP SYN segment to server specifies initial seq # no data Step 2: server host receives SYN, replies with SYNACK segment server allocates buffers specifies server initial seq. # Step 3: client receives SYNACK, replies with ACK segment, which may contain data client server S Y N , C lie n tS e q # Connection request S Y N , A C K , S e r v e r S e q # Connection granted A C K , D A T A ACK 6 TCP Connection: tear down Closing a connection: Step 1: client: closes socket sends TCP FIN control segment to server Step 2: server: receives FIN, replies with ACK closes connection, sends FIN. client server F IN close A C K F I N close 7...
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This note was uploaded on 06/28/2009 for the course CS 372 taught by Professor Leviet during the Fall '07 term at Oregon State.

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Lecture10 - 1 Thursday, May 1 Lab#2 Scores are posted Pick...

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