Transport-layer-TCP

Transport-layer-TCP - Transport Layer Transport Layer...

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1 Csci 232 – Computer Networks Transport Layer & TCP 1 Transport Layer ± Transport Layer Services ± connection-oriented vs. connectionless ± multiplexing and demultplexing ± UDP: Connectionless Unreliable Service ± TCP: Connection-Oriented Reliable Service ± connection management: set-up and tear down ± reliable data transfer protocols ± flow and congestion control Readings: Chapter 5 (5.1, 5.2) Csci 232 – Computer Networks Transport Layer & TCP 2 Transport Protocols • Lowest level end-to- end protocol. – Header generated by sender is interpreted only by the destination – Routers view transport header as part of the payload Transport IP Datalink Physical Transport IP Datalink Physical IP router Csci 232 – Computer Networks Transport Layer & TCP 3 Transport Services and Protocols •p r o v i d e logical communication between app processes running on different hosts • transport protocols run in end systems – send side: breaks app messages into segments , passes to network layer – rcv side: reassembles segments into messages, passes to app layer • more than one transport protocol available to apps – Internet: TCP and UDP application transport network data link physical application transport network data link physical network data link physical network data link physical network data link physical network data link physical network data link physical l o g i c a l e n d - t r s p Csci 232 – Computer Networks Transport Layer & TCP 4 Transport Layer Services • Underlying best-effort network – drops messages – re-orders messages – delivers duplicate copies of a given message – delivers messages after an arbitrarily long delay • Common end-to-end services – guarantee message delivery – deliver messages in the same order they are sent – deliver at most one copy of each message – allow the receiver to flow control the sender – support multiple application processes on each host Csci 232 – Computer Networks Transport Layer & TCP 5 Transport vs. Application and Network Layer application layer: application processes and message exchange network layer: logical communication between hosts transport layer: logical communication support for app processes – relies on, enhances, network layer services Household analogy: 12 kids sending letters to 12 kids • processes = kids • app messages = letters in envelopes •h o s t s = h o u s e s • transport protocol = Ann and Bill • network-layer protocol = postal service Csci 232 – Computer Networks Transport Layer & TCP 6 End to End Issues • Transport services built on top of (potentially) unreliable network service – packets can be corrupted or lost – Packets can be delayed or arrive “out of order” • Do we detect and/or recover errors for apps?
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This note was uploaded on 10/25/2009 for the course CS 232 taught by Professor Susan during the Fall '09 term at GWU.

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Transport-layer-TCP - Transport Layer Transport Layer...

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