ECE544: Communication Networks-II, Spring 2006

1. ECE544: Communication Networks-II, Spring 2006 D. Raychaudhuri Lecture I Includes teaching materials from L. Peterson & L. Govidan

2. Today’s Lecture • Administrative matters • Course Overview • topics covered • design & prototyping projects • Introduction to networking • Elements of top-down design

3. Class Structure • Friday 4:45-7:30pm* • Lecture format • Slides, Board, … • Interactive • Two 80 min sessions • with a 10 min break in between *location will move to WINLAB Modular Conf Room

4. Contact Information • Instructor: Prof. D. Raychaudhuri • Email: ray@winlab.rutgers.edu • Office Hours: by appt, WINLAB Tech Center or Core 501 • TA (for project): Zhibin Wu • Email: zhibinwu@winlab.rutgers.edu • Office hours: tbd • Class Resources (eff 1/23) • Web page: http://www.winlab.rutgers.edu/comnet2 • Mailing list: comnet2@winlab.rutgers.edu

5. Course Readings • Textbook (required, to be used for ~60% material) • Peterson & Davie, “Computer Networks: A Systems Approach”, Morgan Kaufman, 3rd ed • Research papers in networking • to be distributed either online or in class • collection of classical and topical research • ~10 papers and standards documents • required reading to supplement text book overview

6. Course Grading • Class participation & homework: 10% • Brief in-class presentations • Assigned homework from textbook • Midterm (25%) and Final (40%) • Open book, 1 page of notes permitted; includes both descriptive and numerical problems • Design & Prototyping Assignments: 25% • network architecture paper 10% • software project & report 15% • No makeup exams, no extra credit work

7. Student Commitments • Keep up with your reading • read applicable text book chapter and distributed papers/RFC’s before and after each class • Sharpen your programming skills • study C/C++ & Unix programming as needed and work on simple programming exercises early in the semester • Work independently • no “collaboration” of any sort • Turn in assignments on time • Make sure assignments are gradable • follow project and program submission rules

8. Prerequisites • Curricular prerequisites • Computer Networks I or equivalent • General communications and computer architecture/OS background • Skills • C/C++ programming • significant programming project • use of design and analysis tools

9. Introduction Network Principles Shared Media/MAC Pkt switching (ATM) IP Basics IP Advanced Mobility Protocols -- mid-term Network security Transport layer Higher-layer protocols Hardware issues Case studies and research topics www, VOIP semantic routing optical IP network ad-hoc mobile net Course Topics

10. Network architecture paper - select a network - top-down design - requirements - specifications - performance analysis Projects • Warm-up Projects - C/C++programming exercises - Unix sockets, etc. - simple link protocols • Network software project - new network prototype - software platform provided - student teams will write spec & protocol software - system integration & demo • In-class presentations - supplementary topics - ~20 min talk

11. What is the problem? Applications The Global Network Scale Technology Robustness

12. Application Considerations • Application input to network • traffic data rate • traffic pattern (bursty or constant bit rate) • traffic target (multipoint or single destination, mobile or fixed) • Network service delivered to application • delay sensitivity • loss sensitivity

13. A Multimedia Application Chapter 1, Figure 7

14. Reliable File Transfer • Loss sensitive • Not delay sensitive relative to round trip times • Point-to-point or multipoint • Bursty

15. Remote Login • Loss sensitive • Delay sensitive • subject to interactive constraints • can tolerate up to several hundreds of milliseconds • Bursty • Point to point

16. Network Audio • Relatively low bandwidth • Digitized samples, packetized • Delay variance sensitive • Loss tolerant • Possibly multipoint, long duration sessions • natural limit to number of simultaneous senders

17. Network Video • High bandwidth • Compressed video, bursty • Loss tolerance function of compression • Delay tolerance a function of interactivity • Possibly multipoint • Larger number of simultaneous sources

18. Web • Transactional traffic • short requests, possibly large responses • Loss (bug?) tolerant • Delay sensitive • human interactivity • Point-to-point (multipoint is asynchronous)

19. What is…. The Global Network • Structure • Metrics • Failure modes • Functions

20. Network Structure Backbones Regionals Campus LANs

21. Network Metrics • Bandwidth • transmission capacity • Delay • queueing delay • propagation delay (limited by c) • Delay-Bandwidth product • important for control algorithms

22. Bandwidth versus Latency • Relative importance • 1-byte: 1ms vs 100ms dominates 1Mbps vs 100Mbps • 25MB: 1Mbps vs 100Mbps dominates 1ms vs 100ms • Infinite bandwidth • RTT dominates • Throughput = TransferSize / TransferTime • TransferTime = RTT + 1/Bandwidth x TransferSize • 1-MB file to 1-Gbps link as 1-KB packet to 1-Mbps link

23. Delay x Bandwidth Product • Amount of data “in flight” or “in the pipe” • Example: 100ms x 45Mbps = 560KB

24. 10,000 5000 2000 1000 500 1-MB object, 1.5-Mbps link 200 1-MB object, 10-Mbps link Perceived latency (ms) 2-KB object, 1.5-Mbps link 100 2-KB object, 10-Mbps link 50 1-byte object, 1.5-Mbps link 1-byte object, 10-Mbps link 20 10 5 2 1 10 100 R TT (ms) Chapter 1, Figure 9

25. Network Failures • Packet loss • queue overflows • line noise • Node or link failures • Routing transients or failures

26. Statistical Multiplexing Gain 1 Mbps link; users require 0.1 Mbps when transmitting; users active only 10% of the time. • Circuit switching: can support 10 users • Packet switching: with 35 users, probability that >=10 are transmitting at the same time = 0.0004.

27. Back in the old days.. bw Time

28. Then came TDM.. mux demux

29. Logical network view

30. Packet switching (Internet)

31. Packet Switching Interleave packets from different sources • Efficient: resources used on demand • statistical multiplexing • General • multiple types of applications • Accommodates bursty traffic

32. Characteristics of Packet Switching • Store and forward • packets are self contained units • can use alternate paths - reordering • Contention • congestion • delay

33. Protocols • On top of a packet switched network, need • Set of rules governing communication between network elements (applications, hosts, routers) • Protocols define: • format and order of messages • actions taken on receipt of a message

34. Protocols (contd.) • Building blocks of a network architecture • Each protocol object has two different interfaces • service interface: operations on this protocol • peer-to-peer interface: messages exchanged with peer • Term “protocol” is overloaded • specification of peer-to-peer interface • module that implements this interface

35. Layering Teleconferencing User A User B Peers Application Transport Network Link Host Host Layering: technique to simplify complex systems

36. Layering Characteristics • Each layer relies on services from layer below and exports services to layer above • Interface defines interaction • Hides implementation - layers can change without disturbing other layers (black box)

37. ISO Architecture End host End host Application Application Presentation Presentation Session Session Transport Transport Network Network Network Network Data link Data link Data link Data link Physical Physical Physical Physical One or more nodes within the network

38. FTP HTTP NV TFTP UDP TCP IP … NET NET NET 2 1 n Internet Architecture • Defined by Internet Engineering Task Force (IETF) • Hourglass Design • Application vs Application Protocol (FTP, HTTP)

39. Layering General Issues • Reliability • Flow control • Fragmentation • Multiplexing • Connection setup (handshaking) • Addressing/naming (locating peers)

40. Example: Transport layer • First end-to-end layer • End-to-end state • May provide reliability, flow and congestion control

41. Example: Network Layer • Point-to-point communication • Network and host addressing • Routing

42. Host Host Application Host Channel Application Host Host Inter-Process Communication • Turn host-to-host connectivity into process-to-process communication. • Fill gap between what applications expect and what the underlying technology provides.

43. IPC Abstractions • Stream-Based • video: sequence of frames • 1/4 NTSC = 352x240 pixels • (352 x 240 x 24)/8=247.5KB • 30 fps = 7500KBps = 60Mbps • video applications • on-demand video • video conferencing • Request/Reply • distributed file systems • digital libraries (web)

44. Interfaces Host1 Host2 Service High-level High-level interface object object Protocol Protocol Peer-to-peer interface

45. Interfaces (contd.) Chapter 1, Figure 21

46. Interfaces (contd.) Chapter 1, Figure 22

47. Protocol Machinery • Protocol Graph • most peer-to-peer communication is indirect • peer-to-peer is direct only at hardware level Host 2 Host 1 Digital Digital Video Video File File library library application application application application application application RRP MSP RRP MSP HHP HHP

48. Machinery (cont) • Multiplexing and Demultiplexing (demux key) • Encapsulation (header/body) Host 1 Host 2 Application Application program program Data Data RRP RRP RRP Data RRP Data HHP HHP HHP RRP Data

49. Network Architecture • Identify basic service requirements • transport service(s) • bit-rates to be supported • network API • # of users • terminal type (fixed, portable, etc.) • Outline network topology • access network type (wired/wireless, span, etc.) • core network if any (node locations, span, etc.)

50. Example 1: Broadband Wireless Access • Draw a general conceptual network diagram to start... Metro-area wireless access network (~Km) telco-BWA gateway Switched Telecom Network Mobile Comm Devices ~0.1-10 Mbos Broadband Wireless Access Network Mobile PDA/PIA Semi-mobile Laptop, etc. Internet IP-BWA gateway Multiservice interface with voice/data , QoS support, and mobility support Fixed PC/WS