6 - Introduction UDP Stop-and-Wait Go-Back-N Selective...

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Introduction UDP Stop-and-Wait Go-Back-N Selective Repeat Take-Home Points Reliable Transport Fundamentals Sending Data Reliably Across an Unreliable Network Daniel Zappala Brigham Young University Computer Science Department Reliable Transport Daniel Zappala 1/27
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Introduction UDP Stop-and-Wait Go-Back-N Selective Repeat Take-Home Points 1 Introduction 2 UDP 3 Stop-and-Wait 4 Go-Back-N 5 Selective Repeat 6 Take-Home Points Reliable Transport Daniel Zappala 2/27
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Introduction UDP Stop-and-Wait Go-Back-N Selective Repeat Take-Home Points Question of the Day How do you reliably send data across an unreliable network? Reliable Transport Daniel Zappala 3/27
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Introduction UDP Stop-and-Wait Go-Back-N Selective Repeat Take-Home Points Logical Communication and Message Segmentation logical communication between processes running on different hosts network may lose, delay, duplicate, or re-order packets provide an abstraction that two machines are directly connected message segmentation sender divides messages into segments, passes them to network layer receiver reassembles segments into a continuous byte stream Reliable Transport Daniel Zappala 4/27
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Introduction UDP Stop-and-Wait Go-Back-N Selective Repeat Take-Home Points Transport Protocols TCP: reliable service reliable, ordered byte-stream: cope with network events flow control: avoid overwhelming receiver congestion control: avoid overwhelming the network UDP: best-effort service connectionless: no state setup unreliable: lost packets are not re-sent no flow control no congestion control services not available bandwidth guarantees delay guarantees Reliable Transport Daniel Zappala 5/27
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Introduction UDP Stop-and-Wait Go-Back-N Selective Repeat Take-Home Points UDP Header Format defined in RFC 768 port numbers (16 bits each) length of UDP segment, including header (bytes) checksum application data (sometimes called ADU) Reliable Transport Daniel Zappala 6/27
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Introduction UDP Stop-and-Wait Go-Back-N Selective Repeat Take-Home Points UDP Checksum goal: detect some bit errors in transmitted segment sender treat segment (header and data) as a sequence of 16-bit integers take the one’s complement sum of all the entire segment put resulting value in UDP checksum field receiver compute checksum of received segment check if computed checksum = -0 yes – no error detected no – a bit error occurred Reliable Transport Daniel Zappala 7/27
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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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6 - Introduction UDP Stop-and-Wait Go-Back-N Selective...

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