15-744: Computer NetworkingOutlineWho’s Who?ObjectivesWeb PageCourse MaterialsGradingWaitlist & HW 0Class CoverageLecture TopicsSlide 11What is the Objective of Networking?Back in the Old Days…Packet Switching (Internet)Packet SwitchingCharacteristics of Packet SwitchingInternet[work]ChallengeHow 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?Design ConsiderationsSlide 39Goals [Clark88]Slide 41Challenge 1: Address FormatsChallenge 2: Different Packet SizesGateway AlternativesEnd-to-End Argument (Principle 2)Example: Reliable File TransferE2E Example: File TransferDiscussionExamplesInternet & End-to-End ArgumentPrinciple 3Principle 4Principle 5Principle 6Principle 7IP Layering (Principle 8)IP Design WeaknessesChanges Over TimeNew Principles?Slide 60How is IP Design Standardized?IPv4 Header – RFC791 (1981)IP Type of ServiceFragmentationFragmentation is HarmfulPath MTU DiscoveryOther FieldsAddressing in IPAddressing ConsiderationsSlide 71IP AddressesIP Address Classes (Some are Obsolete)Subnet Addressing – RFC917 (1984)SubnettingIPv4 ProblemsIP Address Problem (1991)IP Address Utilization (‘98)IPv4 Routing ProblemsSolution 1 – CIDRClassless Inter-Domain RoutingSolution 2 - NATNAT IllustrationSolution 3 - IPv6IPv6 HeaderIPv6 ChangesSlide 90Summary: Internet ArchitectureSummary: Minimalist ApproachSummary: IP DesignNext Lecture15-744: Computer NetworkingL-1 Intro to Computer NetworksL -1; 9-17-04© Srinivasan Seshan, 2004 2Outline•Administrivia•Layering•Design principles in internetworks •IP designL -1; 9-17-04© Srinivasan Seshan, 2004 3Who’s Who?•Professor: Srinivasan Seshan•http://www.cs.cmu.edu/~srini•[email protected]•Office hours: Friday 4:00-5:00•TA: Vyas Sekar•[email protected]•Office hours: Tuesday 4:00-5:00•Course info•http://www.cs.cmu.edu/~srini/15-744/F04/L -1; 9-17-04© Srinivasan Seshan, 2004 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 researchersL -1; 9-17-04© Srinivasan Seshan, 2004 5Web Page•Check regularly!!•Course schedule•Reading list•Lecture notes•Announcements•Assignments•Project ideas•Exams•Student listL -1; 9-17-04© Srinivasan Seshan, 2004 6Course Materials•Research papers•Links to ps or pdf on Web page•Combination of classic and recent work•~50 papers•Optional readings•Recommended textbooks•For students not familiar with networking•Peterson & Davie or Kurose & RossL -1; 9-17-04© Srinivasan Seshan, 2004 7Grading•Homework assignments •Problem sets & hands-on assignments (15%)•Hand-ins for readings (10%)•Class participation (5%)•2 person project (30%)•Midterm exam (20%)•Final exam (20%)L -1; 9-17-04© Srinivasan Seshan, 2004 8Waitlist & HW 0•Class is heavily over-subscribed•Unlikely to take any more students•Position on waitlist irrelevant •HW 0 – due next class•If you are trying to add class•HW 0 due early – Wednesday to TA•I will email enrollment decisions as early as possibleL -1; 9-17-04© Srinivasan Seshan, 2004 9Class Coverage•Little coverage of physical and data link layer•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?L -1; 9-17-04© Srinivasan Seshan, 2004 10Lecture TopicsTraditional•Layering•Internet architecture•Routing (IP)•Transport (TCP)•Queue management (FQ, RED)•Naming (DNS)Recent Topics•Multicast•Mobility/wireless•Active networks•QOS•Security•Network measurement•Overlay networks•P2P applicationsL -1; 9-17-04© Srinivasan Seshan, 2004 11Outline•Administrivia•Layering•Design principles in internetworks •IP designL -1; 9-17-04© Srinivasan Seshan, 2004 12What 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 sensitivityL -1; 9-17-04© Srinivasan Seshan, 2004 13Back in the Old Days…L -1; 9-17-04© Srinivasan Seshan, 2004 14Packet Switching (Internet)PacketsL -1; 9-17-04© Srinivasan Seshan, 2004 15Packet Switching•Interleave packets from different sources•Efficient: resources used on demand•Statistical multiplexing•General•Multiple types of applications•Accommodates bursty traffic•Addition of queuesL -1; 9-17-04© Srinivasan Seshan, 2004 16Characteristics of Packet Switching•Store and forward•Packets are self contained units•Can use alternate paths – reordering•Contention•Congestion•DelayL -1; 9-17-04© Srinivasan Seshan, 2004 17Internet[work]Internet[work]•A collection of interconnected networks•Host: network endpoints (computer, PDA, light switch, …)•Router: node that connects networks•Internet vs. internetL -1; 9-17-04© Srinivasan Seshan, 2004 18Challenge•Many differences between networks•Address formats•Performance – bandwidth/latency•Packet size•Loss rate/pattern/handling•Routing•How to translate between various network technologies?L -1; 9-17-04© Srinivasan Seshan, 2004 19How To Find Nodes?InternetComputer 1 Computer 2Need naming and routingL -1; 9-17-04© Srinivasan Seshan, 2004 20NamingWhat’s the IP address for www.cmu.edu?It is 128.2.11.43Translates human readable names to logical endpointsLocal DNS ServerComputer 1L -1; 9-17-04© Srinivasan Seshan, 2004 21RoutingRRRRRHHHHRRHRRouters send packet towards destinationH: HostsR: RoutersL -1; 9-17-04© Srinivasan Seshan, 2004 22Meeting Application Demands•Reliability•Corruption•Lost packets•Flow and congestion control•Fragmentation•In-order delivery•Etc…L -1; 9-17-04© Srinivasan Seshan, 2004 23What if the Data gets Corrupted?InternetGET windex.htmlGET index.htmlSolution: Add a chec