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1 Grading Policy Homework and Projects Homework 15% Homeworks: - PDF document

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Course Information CS/ECE 438, CSE 425 Instructor Communication Networks Prof. Nikita Borisov Office Hours: 460 CSL, 244-5385 10-12 Tuesdays nikita@uiuc.edu or by appointment TA Nikita Borisov Monika Battala,

  1. Course Information CS/ECE 438, CSE 425 Instructor  Communication Networks Prof. Nikita Borisov Office Hours:  460 CSL, 244-5385 10-12 Tuesdays nikita@uiuc.edu or by appointment TA  Nikita Borisov Monika Battala, battala2@uiuc.edu  Office hours TBA  ECE Department, UIUC Webpage  http://www.cs.uiuc.edu/class/fa06/cs438  Newsgroup  class.cs438 on news.cs.uiuc.edu  8/25/06 UIUC - CS/ECE 438, Fall 2006 2 Acknowledgments Prerequisites  Slides are adapted from Prof. Kravets  C Programming (CS241)  Some material contributed by Profs.  Pre-req for ECE students is ECE290, but ECE391/398SSL or C experience highly Luo, Lumetta, Hajek, Vaidya recommended  Some material from Larry Peterson &  Probability and Statistics (MATH James Kurose & Keith Ross 461,463 or ECE 413) 8/25/06 UIUC - CS/ECE 438, Fall 2006 3 8/25/06 UIUC - CS/ECE 438, Fall 2006 4 Textbook Recommended Text  Computer Networks: A Top-Down  UNIX Network Programming, Approach Featuring the Internet , by Kurose Volume 1 , by Stevens & Ross, 3rd Edition  There are 3 editions  We will be covering this text out of order  Second & third edition more up-to-date Ch 1   First edition (1990) contains more Ch 5 + some of 6  background on general UNIX Ch 4  programming Ch 3  Some of Ch 2  8/25/06 UIUC - CS/ECE 438, Fall 2006 5 8/25/06 UIUC - CS/ECE 438, Fall 2006 6 1

  2. Grading Policy Homework and Projects  Homework 15%  Homeworks:  7 homework assignments Due Wednesdays at 2:00 in class.  General extension to Fridays at 2:00pm (hard  Mid-term Exam 20%  deadline).  Oct 12 No questions to TA or on newsgroup after class   Programming Projects 35% on Tuesday.  4 Programming projects  Projects:  2% off per hour late Project 1: 5%, Projects 2- 4: 10%   Final Exam 30% Due Fridays at 9:00pm.  8/25/06 UIUC - CS/ECE 438, Fall 2006 7 8/25/06 UIUC - CS/ECE 438, Fall 2006 8 Academic Honesty One Unit Students  Your work in this class must be your own.  Graduate students MAY take an extra unit project in conjunction with this class  Penalties for excessive collaboration and Graduate students cheating are severe  Register for 4 credits   Sharing strategies and small code Write a survey paper in a networking research area of  fragments (5-10 lines) OK your choice.  Sharing homework answers and large Project proposal with list of 10+ academic references  (no URL’s) due September 22 sections of code forbidden Paper due last day of class  Don’t post these to newsgroup!  Undergraduates may not take this project course   If in doubt, ask the professor 8/25/06 UIUC - CS/ECE 438, Fall 2006 9 8/25/06 UIUC - CS/ECE 438, Fall 2006 10 Course Objectives Programming Objectives  At the end of the semester, you should be  At the end of the semester, you able to: should be able to Identify the problems that arise in networked   Identify and describe the purpose of communication each component of the TCP/IP protocol Explain the advantages and disadvantages of  suite existing solutions to these problems in the context of different networking regimes  Develop solid client-server applications using TCP/IP Understand the implications of a given solution  for performance in various networking regimes  Understand the impact of trends in Evaluate novel approaches to these problems  network hardware on network software issues 8/25/06 UIUC - CS/ECE 438, Fall 2006 11 8/25/06 UIUC - CS/ECE 438, Fall 2006 12 2

  3. Course Contents Connectivity  Overview  Building Block  UNIX Network Programming  Links: coax cable, optical fiber, …  Direct Link Networks  Nodes: workstations, routers, …  Multiple Access  Links:  Packet Switched Networks  Internetworking  Point-to-point  Reliable Transport  Congestion Control, QoS & Fair Sharing …  Multiple access  Performance Analysis and Queueing Theory 8/25/06 UIUC - CS/ECE 438, Fall 2006 13 8/25/06 UIUC - CS/ECE 438, Fall 2006 14 Indirect Connectivity Network Problems  Switched Networks  What must a network provide?  Internetworks  Connectivity  Cost-effective Resource Sharing  Recursive definition of a network  Functionality Two or more nodes   Performance connected by a physical link Two or more networks  connected by one or more nodes 8/25/06 UIUC - CS/ECE 438, Fall 2006 15 8/25/06 UIUC - CS/ECE 438, Fall 2006 16 Addressing Effects of Indirect Connectivity  Addressing Nodes receive data on one link and forward it onto the  next -> switching network Unique byte-string used to indicate which node  Circuit Switching is the target of communication  Telephone   Routing Stream-based (dedicated circuit)  Links reserved for use by communication channel The process of determining how to forward   Send/receive bit stream at constant rate messages toward the destination node based  Packet Switching on its address  Internet   Types of Addresses Message-based (store-and-forward)  Unicast: node-specific Links used dynamically   Admission policies and other traffic  Broadcast: all nodes on the network  determine bandwidth Multicast: subset of nodes on the network  8/25/06 UIUC - CS/ECE 438, Fall 2006 17 8/25/06 UIUC - CS/ECE 438, Fall 2006 18 3

  4. Cost-Effective Sharing of Circuit Switching: FDM and TDM Resources Example: FDM  Physical links and switches must be shared 4 users among many users frequency TDM time  Common multiplexing strategies frequency (Synchronous) time-division multiplexing (TDM)  Frequency-division multiplexing (FDM)  time 8/25/06 UIUC - CS/ECE 438, Fall 2006 19 8/25/06 UIUC - CS/ECE 438, Fall 2006 20 Statistical Multiplexing in a Statistical Multiplexing Switch  Statistical Multiplexing (SM) Packets buffered in switch until forwarded  Selection of next packet depends on policy   On-demand time-division multiplexing How do we make these decisions in a fair manner?   Scheduled on a per-packet basis Round Robin? FIFO? How should the switch handle congestion?  Packets from different sources are  interleaved  Uses upper bounds to limit transmission …  Queue size determines capacity per source 8/25/06 UIUC - CS/ECE 438, Fall 2006 21 8/25/06 UIUC - CS/ECE 438, Fall 2006 22 Functionality Channels  Support For Common Services Channel  Goal The abstraction for application-level communication   Meaningful communication between hosts on a  Idea  network Turn host-to-host connectivity into process-to-process Idea   communication Common services simplify the role of applications  Host Host Hide the complexity of the network without overly  APP constraining the application designer Semantics and interface depend on applications Host  APP Request/reply: FTP, HTTP, DNS  Channel Channel Message stream: video-on-demand, video  conferencing Host Host 8/25/06 UIUC - CS/ECE 438, Fall 2006 23 8/25/06 UIUC - CS/ECE 438, Fall 2006 24 4

  5. Channel Implementation Inter-process Communication  Problems typically masked by  Question communication channel abstractions  Where does the functionality belong? Bit errors (electrical interference)  Packet errors (congestion)  Middle (switches)?  Link/node failures Telephone system   Message delays  Edges (end hosts)?  Out-of-order delivery  Internet  Eavesdropping   Goal Fill the gap between what applications expect  and what the underlying technology provides 8/25/06 UIUC - CS/ECE 438, Fall 2006 25 8/25/06 UIUC - CS/ECE 438, Fall 2006 26 Performance Performance ... and to do so while delivering “good” performance. Latency/delay  Time from A to B Bandwidth/throughput   Example: 30 msec (milliseconds) Data transmitted per unit time   Many applications depend on round-trip time (RTT) Example: 10 Mbps   Components Link bandwidth vs. end-to-end bandwidth   Transmission time  Notation  Propagation delay over links  KB = 2 10 bytes  Queueing delays  Mbps = 10 6 bits per second  Software processing overheads  8/25/06 UIUC - CS/ECE 438, Fall 2006 27 8/25/06 UIUC - CS/ECE 438, Fall 2006 28 Performance Notes Delay x Bandwidth Product Speed of Light  channel = pipe  3.0 x 10 8 meters/second in a vacuum   delay = length 2.3 x 10 8 meters/second in a cable  2.0 x 10 8 meters/second in a fiber   bandwidth = area of a cross section Comments  No queueing delays in a direct link  bandwidth x delay product = volume  Bandwidth is not relevant if size = 1bit  Software overhead can dominate when distance is small  Delay Key Point  Latency dominates small transmissions  Bandwidth Bandwidth dominates large  8/25/06 UIUC - CS/ECE 438, Fall 2006 29 8/25/06 UIUC - CS/ECE 438, Fall 2006 30 5

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