15-744: Computer NetworkingOutlineWho’s Who?ObjectivesWeb PageDiscussion SiteSlide 7Course MaterialsGradingClass CoverageLecture TopicsHomework 0Slide 13This/Next Lecture: Design ConsiderationsWhat is the Objective of Networking?Back in the Old Days…Packet Switching (Internet)Packet SwitchingChallengeInternet[work]How To Find Nodes?NamingRoutingMeeting Application DemandsWhat if the Data gets Corrupted?What if Network is Overloaded?What if the Data gets Lost?What if the Data Doesn’t Fit?What if the Data is Out of Order?Lots of Functions NeededWhat is Layering?ProtocolsLayering CharacteristicsLayeringE.g.: OSI Model: 7 Protocol LayersOSI Layers and LocationsIs Layering Harmful?Next Lecture: Design ConsiderationsSlide 3915-744: Computer NetworkingL-1 Intro to Computer Networks2Outline•Administrivia•Layering3Who’s Who?•Professor: Srinivasan Seshan•http://www.cs.cmu.edu/~srini•[email protected]•Office hours: by appt.•TA: Xi Liu•http://www.cs.cmu.edu/~xil•[email protected] •Course info•http://www.cs.cmu.edu/~srini/15-744/F10/4Objectives•Understand the state-of-the-art in network protocols, architectures and applications•Understand how networking research is done•Teach the typical constraints and thought processes used in networking research•How is class different from undergraduate networking (15-441)•Training network programmers vs. training network researchers5Web Page•Check regularly!!•Course schedule•Reading list•Lecture notes/videos•Announcements•Assignments•Project ideas•ExamsDiscussion Site•http://sourcery.cmcl.cs.cmu.edu:4000/•Please visit http://sourcery.cmcl.cs.cmu.edu:4000/ and create an account. Open the collection CMU 15-744: Computer Networks -- Fall 10. You should then add yourself to the collection using the subscription code: ”15744”6Discussion Site•For each lecture, post a brief comment about each paper:•Since I would like to read the reviews before the lecture, you should have this done by 5pm the day before the lecture. •Learn to critique and appreciate systems papers•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?•What would have done differently?•Each student will present a 10 minute broader critique in class once this semester and post longer “public” review once•Looking at related work, etc.•Email signup78Course Materials•Research papers•Links to ps or pdf on Web page•Combination of classic and recent work•~40 papers•Optional readings•Recommended textbooks•For students not familiar with networking•Peterson & Davie or Kurose & Ross9Grading•Homework assignments (15%)•4 Problem sets & hands-on assignments•Class + discussion site participation (10%)•Midterm exam + final exam (35%)•Closed book, in-class•2 or 3 person project (40%)•Main focus of class work•Make project productive for you!10Class Coverage•Little coverage of physical and data link layer•Little coverage of undergraduate material•Students expected to know this•Focus on network to application layer•We will deal with:•Protocol rules and algorithms•Investigate protocol trade-offs•Why this way and not another?11Lecture TopicsTraditional•Layering•Internet architecture•Routing (IP)•Transport (TCP)•Queue management (FQ, RED)•Naming (DNS)Recent Topics•Machine rooms•Mobility/wireless•QoS•Security•Network measurement•Overlay networks•P2P applications+ 2 TBD slotsHomework 0•Email [email protected] & [email protected] •4 lecture choices for critique/public review•1 topic choice for first TBD lecture•1 sentence version of project interest & list of project partner•E.g., I want to apply game theory to network routing.•Register on discussion site•Post response for 1st two papers (extended deadline – 9am Friday)1213Outline•Administrivia•Layering14This/Next Lecture: Design Considerations •How to determine split of functionality•Across protocol layers•Across network nodes•Assigned Reading•[SRC84] End-to-end Arguments in System Design•[Cla88] Design Philosophy of the DARPA Internet Protocols•Optional Reading•[CT90] Architectural Considerations for a New Generation of Protocols15What is the Objective of Networking?•Communication between applications on different computers•Must understand application needs/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)PacketsPacket SwitchingPositives•Interleave packets from different sources•Efficient: resources used on demand•Statistical multiplexing•General•Multiple types of applications•Allows for bursty traffic•Addition of queuesChallenges•Store and forward•Packets are self contained units•Can use alternate paths – reordering•Contention•Congestion•Delay1819Challenge•Many differences between networks•Address formats•Performance – bandwidth/latency•Packet size•Loss rate/pattern/handling•Routing•How to translate between various network technologies?20Internet[work]Internet[work]•A collection of interconnected networks•Host: network endpoints (computer, PDA, light switch, …)•Router: node that connects networks•How do we translate?21How To Find Nodes?InternetComputer 1 Computer 2Need naming and routing22NamingWhat’s the IP address for www.cmu.edu?It is 128.2.11.43Translates human readable names to logical endpointsLocal DNS ServerComputer 123RoutingRRRRRHHHHRRHRRouters send packet towards destinationH: HostsR: Routers24Meeting Application Demands•Reliability•Corruption•Lost packets•Flow and congestion control•Fragmentation•In-order delivery•Etc…25What 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 6X26What 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 Control27What if the Data gets Lost?InternetGET index.htmlProblem: Lost DataInternetGET index.htmlSolution: Timeout and RetransmitGET index.htmlGET index.html28Problem: Packet sizeSolution: Fragment data across
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