Lecture 1 IntroductionToday’s LectureInstructorsCourse GoalsCourse FormatSounds Great! How Do I Get In?Administrative StuffGradingPolicy on CollaborationPolicy on Late Work and RegradingThis WeekWhat Is a Network?Networks Juggle Many GoalsChallenges for NetworksHow to Draw a NetworkBuilding block: The LinksSlide 17Multiplexing!Circuit SwitchingSlide 20Circuit Switching 2Circuit Switching DiscussionPacket Switching (our emphasis)Statistical MultiplexingLocal Area Networks (LANs)Wide Area Networks“The Internet”Challenges of the InternetImplementing Packet-Switched NetworksRoutingNetwork Service ModelUsing NetworksUsing Networks SecurelyApplications1Lecture 1IntroductionDavid AndersenSchool of Computer ScienceCarnegie Mellon University15-441 Networking, Spring 2005http://www.cs.cmu.edu/~srini/15-441/S05/2Today’s LectureCourse outline and goals.Whirlwind Tour of Networking ™3InstructorsTwo instructors.»David Andersen–<[email protected]> , Wean Hall 8206»Srini Seshan–<[email protected]>, Wean Hall 8113N teaching assistants.»Ed Bardsley [email protected] - WeH 5201 cluster»Eric Burns - [email protected] – NSH 4511»David Craft [email protected] – WeH 7th whiteboard»2 more TBA4Course GoalsBecome familiar with the principles and practice of data networking.»Routing, transport protocols, naming, ...Learn how to write applications that use the network.»How does a web server work?Get some understanding about network internals in a hands on way.»By building a simple network in software5Course Format~30 lectures.»Cover the “principles and practice”»Readings are posted beforehand3 “paper” homeworks.»Do you understand and can you apply the material?»Feedback to students and instructors2 “lab” homeworks.»Illustrate networking conceptsMid-term and final.2 programming projects.»How to use and build networks / networked applications»Application layer; include key ideas from kernel»Larger, open-ended group projects. Start early!6Sounds Great!How Do I Get In?Currently 99 people are enrolled, and 9+ people are on the waiting list.»There is room for 107 students»In other words: your chances of getting in are very goodWe give preference to students attending class.»Look me up after class»All else being equal, we go FCFS.If you do not plan to take the course, please drop it ASAP so somebody else can take your place!7Administrative StufWatch the course web page.»Handouts, readings, ..Read courses bboards.»“Announce” for official announcements»“General” for questions/answersOffice hours posted on web page.Course secretary»Barbara Grandillo, Wean Hall 8018Srini – no office hours this week»Office hours start ThursdayBooks – have people gone to the bookstore? How many copies? Should be there…8GradingRoughly equal weight in projects and testing on course contents.20% for Project I 25% for Project II 15% for Midterm 25% for Final exam 15% for HomeworksYou need to demonstrate competence in both projects and tests to pass the course.9Policy on CollaborationWorking together is important.»Discuss course material in general terms»Work together on program debugging, ..Parts must be your own work»Homeworks, midterm, finalProjects: Teams of two»Collaboration, group project skills»Both students should understand the entire projectWeb page has details.10Policy on Late Work andRegrading No assignments with a “short fuse”.»Homeworks: ~1 week»Projects: ~5 weeksLate work will receive a 10% penalty/day.»No penalty for a limited number of handins - see web page»No assignment can be more than 2 days lateOnly exception is documented illness and family emergenciesStart on time!»Every year some students discover that a 4 week project cannot be completed in a weekRequests for regrading must be submitted in writing with course secretary within 2 weeks.»Regrading will be done by original grader11This WeekIntro – what’s this all about?Network programming review.»Socket programming (213 review++)»Project management (RCS, etc.)Outline»Low-level (physical, link, circuits, etc.) »Internet core concepts (addressing, routing, DNS)»Advanced topicsOn to the good stuff…12What Is a Network?Collection of nodes and links that connect themThis is vague. Why? Consider different networks:»Internet»Andrew»Telephone»Your house»Others – sensor nets, cell phones, …Focus on Internet, but understand important common issues and challenges13Networks Juggle Many GoalsEfficiency – resource use; costThe “ilities”:»Evolvability»Managability»Security (securability, if you must)»Ease of:–Creation–Deployment–Management–Creating useful applications»Scalability14Challenges for NetworksGeographic scope»The Internet vs. Andrew, etc.Scale»The Internet vs. your home networkApplication types»Email vs. VideoconferencingTrust and Administration»Corporate network – one network “provider”»Internet – 17,000 network providers15How to Draw a NetworkNode Link Node16Building block: The LinksElectrical questions»Voltage, frequency, …»Wired or wireless?Link-layer issues: How to send data? »When to talk – can everyone talk at once?»What to say – low-level format?»Stay tuned for lecture 5Okay… what about more nodes?Node Link Node17… But what if we want more hosts?Scalability?!One wireWires for everybody!18Multiplexing!Need to share network resourcesHow? Switched network»Party “A” gets resources sometimes»Party “B” gets them sometimesInterior nodes act as “Routers” or “Switches”What mechanisms can share resources?19Circuit SwitchingSource first establishes a connection (circuit) to the destination.»Each router or switch along the way may reserve some bandwidth for the data flowSource sends the data over the circuit.»No need to include the destination address with the data since the routers know the pathThe connection is torn down.Example: telephone network (analog).20Circuit SwitchingSource first establishes a connection (circuit) to the destination.Source sends the data over the circuit.»e connection is torn down.Example: telephone network»Early early versions: Human-mediated switches.»Early versions: End-to-end electrical connection!»Today: Virtual circuits or lambda switching21Circuit
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