lect13a_AppLay_Ross

lect13a_AppLay_Ross - Application Layer Lecture 13a...

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1 Application Layer Lecture 13a ELEC300U * The slides are adapted from ppt slides (in substantially unaltered form) available from “Computer Networking: A Top-Down Approach,” 4 th edition, by Jim Kurose and Keith Ross, Addison-Wesley, July 2007. Part of the materials are also adapted from ELEC315 and MIT 6.02 course notes. A brief discussion of transport- layer protocols – TCP, UDP Key application-layer concepts DNS Web and HTTP
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2 Internet protocol stack application: supporting network applications HTTP, SMTP, FTP, DNS transport: process-process data transfer TCP, UDP network: routing of datagrams from source to destination IP, routing protocols link: data transfer between neighboring network elements 802.11, Ethernet physical: bits “on the wire” Application Transport Network Link Physical
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3 Packets in a Best-Effort Network Lead a Rough Life Can be lost for any number of reasons No current route Current route not working properly Queue overflow at switch (due to congestion) Packet corruption (noise/interference), collisions Uncorrectable errors detected Queue overflow at receiving node Can arrive out-of-order And experience variable delays
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4 Transport Layer Transport layer “cleans up” best-effort behavior to present clean abstraction Common functions (not all needed for apps, so multiple transport layer choices) Reliability Ordering Data integrity (detect corruption) Timeliness (“remove” variable latency) Flow and congestion control: for performance
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5 Transport services and protocols provide 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 l o g i c a e n d -e d t ra s p r
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6 Internet transport-layer protocols reliable, in-order delivery (TCP) congestion control flow control connection setup unreliable, unordered delivery: UDP no-frills extension of “best-effort” IP services not available: delay guarantees bandwidth guarantees 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 network data link physical application transport network data link physical l o g i c a e n d -e d t ra s p r
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7 Internet transport protocols services TCP service: connection-oriented: setup required between client and server processes reliable transport between sending and receiving process flow control: sender won’t overwhelm receiver congestion control:
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This note was uploaded on 01/28/2011 for the course ELEC 300U taught by Professor Rossmurchandaminebermak during the Fall '08 term at HKUST.

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lect13a_AppLay_Ross - Application Layer Lecture 13a...

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