Welcome to CS 340Introduction to Computer NetworkingSome slides are in courtesy of J. Kurose and K. RossOverview• Course Administrative Trivia• Internet Architecture• Network Protocols•Network Edge• A taxonomy of communication networks• Top-down Intro Networking Class– Application down to physical layer•Small Class– More attention to each student• Topics to Cover– Overview of Internet architecture, protocols– Network applications (HTTP, FTP) and programming– Transport (TCP, UDP), congestion/flow control – Network (IP), routing, multicast – Data Link, error handling, LAN, wirelessCourse OverviewLogistics• InstructorYan Chen ([email protected]), Office Hours: Th. 2-4pm or by appointment, Rm330, 1890 Maple Ave. •TAAshish Gupta ([email protected]) Office Hours: Tu. and Th. 11am - noon(12pm), Rm 240, Maple Ave.Prerequisites• A LOT OF WORK – Heavy Projects– Build a TCP stack and a Web server that runs on it– IP routing• Required: CS311 (data structure)• Highly Recommended: OS or having some familiarity with Unix systems programming, preferably in C or C++– Minet is in C++ / STL– BUILDING software is 50% of the grade of this classCourse Materials• Computer Networking: A Top-Down Approach Featuring the Internet, Second Edition, James Kurose and Keith Ross, Addison Wesley, 2002 • TCP/IP Illustrated, Volume I: The Protocols, Richard Stevens, Addison Wesley, 1994 • See course webpage and syllabus for other recommended books and referencesGrading• Homeworks (4 sets) 10%• Projects 50% – Web client/server 10%– TCP stack 25%– IP routing 15%• Midterm 20%• Final 20%– Exams in-class, closed-book, non-cumulative• Late policy: 10% each day after the due date•No cheatingCommunication• Web page: http://www.cs.nwu.edu/~ychen/classes/cs340/• Recitation: Wed., 4-5pm, Room 381, 1890 Maple.– TA lectures on the homework and projects, and help to prepare the exams. • Newsgroup are available– cs.340.annouce (course announcement)– cs.340.discuss (posting Q & A)• Send emails to instructor and TA for questions inappropriate in newsgroupOverview• Course administrative trivia• Internet Architecture• Network Protocols•Network Edge• A taxonomy of communication networksWhat’s the Internet: “nuts and bolts” view• Millions of connected computing devices: hosts, end-systems– PCs, servers– PDAs, phones, toasters, shoesrunning network apps•Communication links– Fiber, cable, radio, satellite– Residential access: modem, DSL, cable modem, satellite–Transmission rate = bandwidth•Routers:forward packets (chunks of data)local ISPcompanynetworkregional ISProuterworkstationservermobileNetwork Components (Examples)FibersCoaxial CableLinks Interfaces Switches/routersEthernet cardWireless cardLarge routerTelephoneswitchWhat’s the Internet: “nuts and bolts” view•protocolscontrol sending, receiving of msgs– e.g., TCP, IP, HTTP, FTP•Internet: “network of networks”– loosely hierarchical– public Internet versus private intranet• communication infrastructure enables distributed applications:– Web, email, games, e-commerce, database., voting, file (MP3) sharinglocal ISPcompanynetworkregional ISProuterworkstationservermobileHistory of the Internet• 70’s: started as a research project, 56 kbps, < 200 computers• 80-83: ARPANET and MILNET split • 85-86: NSF builds NSFNET as backbone, links 6 Supercomputer centers, 1.5 Mbps, 10,000 computers• 87-90: link regional networks, NSI (NASA), ESNet(DOE), DARTnet, TWBNet (DARPA), 100,000 computers• 90-92: NSFNET moves to 45 Mbps, 16 mid-level networks• 95: NSF backbone dismantled, multiple private backbones• Today: backbones run at 10 Gbps, close to 200 millions computers in 150 countriesGrowth of the Internet• Number of Hosts on the Internet:Aug. 1981 213Oct. 1984 1,024Dec. 1987 28,174 Oct. 1990 313,000 Oct. 1993 2,056,000Apr. 1995 5,706,000Jan. 1997 16,146,000Jan. 1999 56,218,000Jan. 2001 109,374,000Jan 2003 171,638,29711010010001000010000010000001000000010000000010000000001981 1984 1987 1990 1993 1996 1999 2002Data available at: http://www.isc.org/Backbone (Teleglobe)Overview• Course administrative trivia• Internet Architecture• Network Protocols•Network Edge• A taxonomy of communication networksWhat’s a protocol?human protocols:• “what’s the time?”• “I have a question”• introductions…specific msgs sent… specific actions taken when msgs received, or other eventsnetwork protocols:• machines rather than humans• all communication activity in Internet governed by protocolsprotocols define format, order of msgs sent and received among network entities, and actions taken on msg transmission, receiptWhat’s a protocol?a human protocol and a computer network protocol:HiHiGot thetime?2:00TCP connectionreqTCP connectionresponseGet http://www.cs.nwu.edu<file>timeOverview• Course administrative trivia• Internet Architecture• Network Protocols•Network Edge• A taxonomy of communication networksThe Network Edge• End systems (hosts):– run application programs– e.g. Web, email– at “edge of network”•Client/server model– client host requests, receives service from always-on server– e.g. Web browser/server; email client/server• Peer-to-peer model:– minimal (or no) use of dedicated servers– e.g. Gnutella, KaZaANetwork Edge: Connection-oriented ServiceGoal:data transfer between end systems•handshaking:setup (prepare for) data transfer ahead of time– Hello, hello back human protocol–set up “state”in two communicating hosts• TCP - Transmission Control Protocol – Internet’s connection-oriented serviceTCP service [RFC 793]•reliable, in-orderbyte-stream data transfer– loss: acknowledgements and retransmissions•flow control:– sender won’t overwhelm receiver•congestion control:–senders “slow down sending rate” when network congestedNetwork Edge: Connectionless ServiceGoal:data transfer between end systems– same as before!•UDP- User Datagram Protocol [RFC 768]: Internet’s connectionless service– unreliable data transfer– no flow control– no congestion controlApp’s using TCP:• HTTP (Web), FTP (file transfer), Telnet (remote login), SMTP (email)App’s using UDP:• streaming media, teleconferencing, DNS, Internet telephonyOverview• Course administrative trivia•