02app_pt1 - 02 AppLayer_pt1 25 Jan 2011 SCD58 Computer...

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Unformatted text preview: 02 AppLayer_pt1 25 Jan 2011 SCD58 Computer Networks 1 02 AppLayer_pt1 CSCD58S Computer Networks 1 02 AppLayer_pt1 25 Jan 2011 SCD58 Computer Networks 2 02apps CSCD58S Computer Networks 2 Chapter 2 roadmap b 2.1 Principles of app layer protocols c clients and servers c app requirements b 2.2 Web and HTTP b 2.3 FTP b 2.4 Electronic Mail c SMTP, POP3, IMAP b 2.5 DNS b 2.6 P2P applications b 2.8 Socket programming with TCP b 2.7 Socket programming with UDP 02 AppLayer_pt1 25 Jan 2011 SCD58 Computer Networks 3 02apps CSCD58S Computer Networks 3 Part 2: Application Layer Our goals: b conceptual + implementation aspects of network application protocols c client server paradigm c service models b learn about protocols by examining popular application-level protocols More chapter goals b specific protocols: c http c ftp c smtp + pop c P2P file-sharing c dns b programming network applications c socket programming 02 AppLayer_pt1 25 Jan 2011 SCD58 Computer Networks 4 02apps CSCD58S Computer Networks 4 Some network apps Some network apps b e-mail b web b instant messaging b remote login b P2P file sharing b multi-user network games b streaming stored video clips b social networks b voice over IP b real-time video conferencing b grid computing 02 AppLayer_pt1 25 Jan 2011 SCD58 Computer Networks 5 02apps CSCD58S Computer Networks 5 Applications and application Applications and application-- layer protocols layer protocols Application: communicating, distributed processes c running on network hosts in user space c exchange messages to implement application c e.g., email, file transfer, the Web Application-layer protocols c one piece of an app c define messages exchanged by apps and actions taken c uses services provided by lower layer protocols application transport network data link physical application transport network data link physical application transport network data link physical 02 AppLayer_pt1 25 Jan 2011 SCD58 Computer Networks 6 02apps CSCD58S Computer Networks 6 Network applications: some jargon Network applications: some jargon b A process is a program that is running within a host. b Within the same host, two processes communicate with interprocess communication defined by the OS. b Processes running in different hosts communicate with an application-layer protocol b A user agent is an interface between the user and the network application. c Web:browser c E-mail: mail reader c streaming audio/video: media player 02 AppLayer_pt1 25 Jan 2011 SCD58 Computer Networks 7 02apps CSCD58S Computer Networks 8 Client Client-- server architecture server architecture server: c always-on host c permanent IP address c server farms for scaling clients: c communicate with server c may be intermittently connected c may have dynamic IP addresses c do not communicate directly with each other client/server 02 AppLayer_pt1 25 Jan 2011 SCD58 Computer Networks 8 02apps CSCD58S Computer Networks 9 Google Data Google Data Centers Centers b Estimated cost of data center: $600M b Google spent $2.4B in 2007 on new data centers b Each uses 50-100 megawatts of power 02 AppLayer_pt1...
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02app_pt1 - 02 AppLayer_pt1 25 Jan 2011 SCD58 Computer...

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