CS 268: Computer NetworkingL-1 Intro to Computer Networks2Outline• Administrivia• Layering3Dramatis Personae• Professor: Randy H. Katz• Web: http://www.cs.Berkeley.edu/~randy• Facebook:http://berkeley.facebook.com/people/Randy_Howard_Katz/1241523• Email: [email protected]• Office hours: Tu 1:00-2:00, W 3:00-4:00, 413 Soda Hall• Sorry, no Teaching Assistant!• Course Info• Web: http://www.cs.Berkeley.edu/~randy/Courses/CS268.F08• Blog: http://cs268computernetworking.blogspot.com/• Group: http://www.facebook.com/group.php?gid=382160232324Goals and Objectives• Understand state-of-the-art in networkprotocols, architectures, and applications• Understand process of networking research• Typical constraints and thought processes usedin networking research• Different from undergraduate networking(EECS 122)• i.e., training network programmers vs. trainingnetwork researchersWhen Thinking About Research …“Look for what is so obvious to everyone else thatit’s no longer on their radar, and put it on yours.Seek to uncover assumptions so implicit, they areno longer being questioned. Question them.”• Rodney Brooks, Co-director of CSAIL, MITParticularly relevant advice for network research• Is the current network architecture and decisonsappropriate for wireless networks, sensor networks,real-time networks, enterprise networks, datacenternetworks, etc.?6Web Page• Check regularly!!• Course schedule• Reading list• Lecture notes• Announcements• Project ideas• ExamsCS 268 Blog Assignments• For each lecture, you will create a “publicreview” of paper(s) due for that class that:• Briefly summarizes paper (1-2 paragraphs)• Provides background/related material(1-2 paragraphs)• Critiques paper and suggests discussion topics(2-3 paragraph)• Try to be positive…• Why or why not keep this paper in syllabus?• What issues are left open for future research?• What are the important implications of the work?78Materials on Course Syllabus Page• Research papers• Links to pdfs on Web page• Two papers per class meeting• Combination of classic and recent work• ~40 papers• Lecture Notes• ppt posted, but I will minimize its in-class usage• Seminar/discussion style and participation counts!• Recommended textbooks• For those who need to review their networkingbackground• Peterson & Davie/4ed or Kurose & Ross/4ed9Course Grading• Class + paper blog participation (20%)• Makes sure that you read the papers beforeclass• Two person research project (40%)• Substantial independent research project• You learn a lot by working together• Several class meetings dedicated to projects• Two Quizzes (40%)• Closed book, in-class• Makes sure that you understood the papersWhat about the Waitlist?• We should be able to accommodate allgraduate students who want to take the class• Undergraduate students should talk to me todetermine if this is the right course for them• Undergraduates will have to partner with anotherundergrad to do a research project1011Class Topic Coverage• Little on physical and data link layer• Little on undergraduate material• Supposedly you already know this, though somerevisiting/overlap is unavoidable• Focus on the why, not the what• Focus on network to application layer• We will deal with:• Protocol rules and algorithms• Investigate protocol trade-offs• Why this way and not another?12Lecture TopicsTraditional• Layering• Internet architecture• Routing (IP)• Transport (TCP)• Queue management(FQ, RED)• Naming (DNS)Recent Topics• Multicast• Mobility/wireless• Active networks• QoS• Network measurement• Overlay networks• P2P applications• Datacenter networkingLaptop Policy• Should we have an open/closed laptoppolicy?• Good for viewing/annotating papers andelectronic note taking• Bad for distractions (chat, ebay,email, facebook, solitaire, twitter,etc., ...)• Class vote -- you choose!14Outline• Administrivia• Layering15What is the Objective of Networking?• Communication between applications ondifferent computers• Must understand applicationneeds/demands• Traffic data rate• Traffic pattern (bursty or constant bit rate)• Traffic target (multipoint or single destination,mobile or fixed)• Delay sensitivity• Loss sensitivity16Back in the Old Days…17Packet Switching (Internet)Packets18Packet Switching• Interleave packets from different sources• Efficient: resources used on demand• Statistical multiplexing• General• Multiple types of applications• Accommodates bursty traffic• Addition of queues19Characteristics of Packet Switching• Store and forward• Packets are self contained units• Can use alternate paths – reordering• Contention• Congestion• Delay20Internet[work]Internet[work]• A collection ofinterconnectednetworks• Host: networkendpoints(computer, PDA,light switch, …)• Router: node thatconnects networks• Internet vs. internet21Challenge• Many differences between networks• Address formats• Performance – bandwidth/latency• Packet size• Loss rate/pattern/handling• Routing• How to translate between various networktechnologies?22How To Find Nodes?InternetComputer 1 Computer 2Need naming and routing23NamingWhat’s the IP address for www.cmu.edu?It is 128.2.11.43Translates human readable names to logical endpointsLocal DNS ServerComputer 124RoutingRRRRRHHHHRRHRRouters sendpacket towardsdestinationH: HostsR: Routers25Meeting Application Demands• Reliability• Corruption• Lost packets• Flow and congestion control• Fragmentation• In-order delivery• Etc…26What if the Data gets Corrupted?InternetGET windex.htmlGET index.htmlSolution: Add a checksumProblem: Data Corruption0,9 9 6,7,8 21 4,5 7 1,2,3 6X27What if Network is Overloaded?Problem: Network Overload• Short bursts: buffer• What if buffer overflows?• Packets dropped• Sender adjusts rate until load = resources “congestion control”Solution: Buffering and Congestion Control28What if the Data gets Lost?InternetGET index.htmlProblem: Lost DataInternetGET index.htmlSolution: Timeout and RetransmitGET index.htmlGET index.html29Problem: Packet sizeSolution: Fragment data across packetsWhat if the Data Doesn’t Fit?• On Ethernet, max IP packet is 1.5kbytes• Typical web page is 10kbytesGETindex.htmlGET index.html30Solution: Add Sequence NumbersProblem: Out of OrderWhat if the Data is Out of
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