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U of I CS 241 - Introduction to Networking

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Introduction to Networking CS241 AdministrativeContentMotivationNetwork CategoriesNetwork Categories What’s the InternetThe network edge:Client-Server ModelClient-Server ModelCommunication ChannelNaming of Servers and ClientsPortsifconfig – configure network interface on Linux ipconfig – show network address information on Windows show Ethernet addresKinds of CommunicationExamples of Protocols for Client-Server Process Communication TCP/IP Protocol LayersConnection-oriented Communication Protocol Connection-Oriented Communications Illustration Connection-Oriented Server StrategiesMultiple Clients (Serial-server Strategy)Parent-server Strategy Threaded-server StrategySummaryCS 241 Spring 2007System Programming1Introduction to Networking Lecture 34Klara Nahrstedt2CS241 Administrative Read Stallings Chapter 13, R&R 18.1-18.3 LMP3 Start Early!!!3ContentCommunication Motivation Network Categories and Applications Client-Server ModelCommunication ChannelsNaming of Client/ServerTypes of Communication and ProtocolsConnection-oriented Server Strategies4MotivationShare: workstation, PC, Cray, database, radio telescope, work resource sharing computation speed up reliability communication Emails, web queries, on-line banking, internet game, chat…5Network CategoriesResource Sharing Networks. Communication is typically between a user process on one host and a resource manager process on another host. Examples:Access remote files Transfer files between hosts Database distributed among hosts Access peripheral device (e.g., printer) on remote host Distributed Computation Networks.A group of processes cooperating in one activity are distributedover several hosts throughout a network. Examples:Large database systems Real time process-control systems6Network Categories Remote Communication Networks. Typically a batch system with most facilities in one or a few central locations, accessed from many remote locations. Examples:Bank ATMs7What’s the InternetbackboneISPsregionalISPslocal ISPs•enterprise•campus, ...end systems•hosts, servers•pdas, mobiles• network of networks: loosely hierarchical• communication links: fiber, copper, radio, satellite• routers:forward data packets• end-systemsrun network apps• protocols:TCP, IP, HTTP, FTP, PPP, ...8The network edge:• end systems (hosts):– run application programs– e.g., WWW, email– at “edge of network”• client/server model– client host requests, receives service from server– e.g., WWW client (browser)/ server; email client/server9Client-Server Model10Client-Server Model•The client-server model is used in many types of network communication including – mail, ftp, telnet, rlogin, http, and nfs. • In this model, the server waits for requests and the client makes requests for service from the server. Server ClientCommunication ChannelExchange MessagesCommunication End Point Communication End Point11Communication ChannelAsymmetric Ch.Symmetric ChannelTwo-way ChannelOne way ChannelSCSCSCSC12Naming of Servers and ClientsIn Network environment – naming is difficultPossible Server naming by Process ID and Host IDProblem: Client cannot know the process ID of the server process on a host in advanceMost common naming – use address of host(Internet address) and an integer called port number13PortsPorts < 1024, standardPorts > 1024, user createdWell-known Port Numbers mail: 25 ftp: 21 telnet: 23 rlogin 513 http: 80 nfs: 2049 IP address (161.25.19.8)14ifconfig – configure network interface on Linuxipconfig – show network address information on Windows show Ethernet address, Internet address, DNS addressipconfig /all – show all15Kinds of CommunicationConnectionless communicationThe client makes a request to an endpoint on a server and the server can respond to the client's endpoint No handshake required before sending messgesAnalogy: ordinary mail Connection-oriented communicationThe client sets up a connection using the server's well-known port number and then communicates over a private communications channel as shownAnalogy: telephone16Examples of Protocols for Client-Server Process Communication Connectionless – UDP (Unreliable Datagram Protocol)Unreliable – no retransmission Connection-oriented – TCP (Transmission Control Protocol Hand-shake between initiator and destinationReceiver sends acknowledgementIn case sender does not get acknowledgement within certain time,it retransmits message (packet)Flow Control17klara|csil-linux1|~|[2]% netstatActive Internet connections (w/o servers)Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 csil-linux1.cs.uiuc.edu:800 dcsfiles.cs.uiuc.edu:nfs ESTABLISHED tcp 0 0 csil-linux1.cs.uiuc.e:56492 csil-projects.cs.uiuc:mysql ESTABLISHED tcp 0 0 csil-linux1.cs.uiuc.e:56593 dcsfiles.cs.uiuc.edu:sunrpc TIME_WAIT tcp 0 0 csil-linux1.cs.uiuc.e:56594 dcsfiles.cs.uiuc.edu:nfs TIME_WAIT tcp 0 0 csil-linux1.cs.uiuc.edu:799 dcshome.cs.uiuc.edu:nfs ESTABLISHED tcp 1 0 csil-linux1.cs.uiuc.e:38887 ad-dc-p2.ad.uiuc.edu:ldaps CLOSE_WAIT tcp 0 0 csil-linux1.cs.uiuc.e:56590 dcs-ldap1.cs.uiuc.edu:ldap TIME_WAIT tcp 0 0 csil-linux1.cs.uiuc.e:56602 dcs-ldap1.cs.uiuc.edu:ldap TIME_WAIT tcp 1 0 csil-linux1.cs.uiuc.e:55284 ad-dc-p2.ad.uiuc.edu:ldaps CLOSE_WAIT tcp 0 0 csil-linux1.cs.uiuc.e:32780 dcs-ldap1.cs.uiuc.edu:ldap ESTABLISHED tcp 1 0 csil-linux1.cs.uiuc.e:50378 ad-dc-p2.ad.uiuc.edu:ldaps CLOSE_WAIT tcp 0 0 csil-linux1.cs.uiuc.e:38888 dcs-ldap1.cs.uiuc.edu:ldap ESTABLISHED tcp 0 0 csil-linux1.cs.uiuc.edu:ssh 74-134-234-93.dhcp.ins:2057 ESTABLISHED tcp 0 0 csil-linux1.cs.uiuc.edu:ssh darmstadt.cs.uiuc.edu:1605 ESTABLISHED tcp 0 0 csil-linux1.cs.uiuc.edu:ssh 74-134-234-93.dhcp.ins:3025 ESTABLISHED tcp 0 0 csil-linux1.cs.uiuc.edu:ssh seclab-tehran2.cs.uiuc:2555 ESTABLISHED tcp 0 0 csil-linux1.cs.uiuc.edu:ssh sydney.cs.uiuc.edu:1980 ESTABLISHED Active UNIX domain sockets (w/o servers)Proto RefCnt Flags Type State I-Node Pathunix 2 [ ] DGRAM 9167 @/var/run/hal/hotplug_socketunix 2 [ ] DGRAM 3425 @udevdunix 16 [ ] DGRAM 7674 /dev/logunix 2 [ ] DGRAM 1634536 unix 3 [ ] STREAM CONNECTED 163417918TCP/IP Protocol LayersEND USER APPLICATIONIEEE802.XIPTCP UDPFTP, TELNET, SMTP, NSP,


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U of I CS 241 - Introduction to Networking

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