1. 1 Computer Network Architecture ECE 156 Fall 2011 Romit Roy Choudhury Dept. of ECE and CS

2. 2 Course Logistics

3. 3 Welcome to ECE 156 Timings: M/W 1:15pm to 2:30pm Location:Teer 115 Course TA:Di Zhou, Tim Calloway (more info soon) Instructor: Romit Roy Choudhury Faculty in ECE & CS. Ph.D from UIUC in Summer, 2006 Research in Wireless Networking and Mobile Computing Office hours:M/W 3pm - 4pm or appointment Email me at romit.rc@duke.eduromit.rc@duke.edu and visit me at 203 Hudson Hall

4. 4 Welcome to ECE 156 Prerequisite:ECE 52 Else, come and talk to me Further courses:  ECE 256: Wireless Networking and Mobile Computing Spring 2012  CPS 296: Hot Topics in Networked Systems  CPS 214: Computer Network and Distributed Systems

5. 5 Welcome to ECE 156 Course Website: http://www.ee.duke.edu/~romit/courses/f11/ece156-f11-networking.html  Most course related information will be posted on the website Please check the course website frequently

6. 6 Welcome to ECE 156 Make up classes  Will be occasionally necessary due to travel  Would like to schedule on a case by case basis

7. 7 Welcome to ECE 156 Grading:  Participation/Presentation:10%  Homework:20%  Programming Assignments:20%  1 mid-term exam:20%  Final exam:30%  Programming project may be in groups of 2  One of the exams is likely to be open book

8. 8 Finally Academic honesty  Please please please …  A few points is not worth a tarnished career  In the long run, GPA does not matter as much as you think it does

9. 9 Course Summary (Very Briefly)

10. 10 Course information  Course materials:  Text: Computer Networking: A Top Down Approach Featuring the Internet, J. Kurose & K. Ross, Addison Wesley, 3 rd ed., 2005, or higher  Class notes/slides  Acknowledgment to Jim Kurose  Some supplementary reading material

11. 11 What is this course about? Introductory (first) course in computer networking  Undergrads, early MS students  learn principles of computer networking  learn practice of computer networking  Internet architecture/protocols as case study  Real wireless networks as case studies  Intro to next generation networking

12. 12 Course information  By the time you are finished …  You understand variety of concepts (not just factoids)  Internet, HTTP, DNS, P2P, …  Sockets, Ports, …  Congestion Control, Flow Control, TCP, …  Routing, Basic Graphs, Djikstra’s Algorithm, IP, …  DSL Vs Cable, Aloha, CSMA, TDMA, Token, WiFi 802.11, …  Security, RSA, …  Cellular Networks, Mobile Networks, Satellite Networks, …  Wireless Multihop Networks (ad hoc, mesh, WLANs)  Sensor Networks  … If you understand 75% of these terms, you shouldn’t be here

13. 13 What this Course Does Not Cover Not a “communications” course Does not cover  Modulation schemes  Transmitter/Receiver design  Signal processing and antenna design  Etc. This is course on  Understading, analysing, and (perhaps) designing of protocols and algorithms in networking systems (wired Internet/Ethernet and wireless cell/WiFi)

14. 14 What’s the difference between Communications And Networking

15. 15 Finally I cannot / will not / should not be speaking alone in class  Questions  Comments  Disagreements  Debates … are highly encouraged This course can be real fun Whether it will be …  Is up to you and me

16. 16 Hello! I am ECE 156

17. 17 Computer Network Architecture Past, Present, and Future

18. 18 On the Shoulders of Giants 1961: Leonard Kleinrock published a work on packet switching 1962: J. Licklider described a worldwide network of computers called Galactic Network 1965: Larry Roberts designed the ARPANET that communicated over long distance links 1971: Ray Tomilson invents email at BBN 1972: Bob Kahn and Vint Cerf invented TCP for reliable packet transport

19. 19 On the Shoulders of Giants … 1973: David Clark, Bob Metcalfe implemented TCP and designed ethernet at Xerox PARC 1975: Paul Mockapetris developed DNS system for host lookup 1980: Radia Perlman invented spanning tree algorithm for bridging separate networks Things snowballed from there on …

20. 20 What we have today is beyond any of the inventors’ imagination …

21. 21 And YOU are here

22. 22 And by “YOU” I mean …

23. 23 “Cool” internet appliances World’s smallest web server http://www-ccs.cs.umass.edu/~shri/iPic.html IP picture frame http://www.ceiva.com/ Web-enabled toaster + weather forecaster Internet phones

24. 24 And Of Course people …

25. 25 InterNetwork Millions of end points (you, me, and toasters) are connected over a network  Many end points can be addressed by numbers  Many others lie behind a virtual end point Many networks form a bigger network The overall strcture called the Internet  With a capital I  Defined as the network of networks

26. 26 Internet structure: network of networks roughly hierarchical at center: “tier-1” ISPs (e.g., MCI, Sprint, AT&T, Cable and Wireless), national/international coverage  treat each other as equals Tier 1 ISP Tier-1 providers interconnect (peer) privately

27. 27 Tier-1 ISP: e.g., Sprint Sprint US backbone network Seattle Atlanta Chicago Roachdale Stockton San Jose Anaheim Fort Worth Orlando Kansas City Cheyenne New York Pennsauken Relay Wash. DC Tacoma DS3 (45 Mbps) OC3 (155 Mbps) OC12 (622 Mbps) OC48 (2.4 Gbps) … to/from customers peering to/from backbone ….…. … … … POP: point-of-presence

28. 28 Cables Laid Out in the Oceans Optical Fiber cross-section

29. 29 Cable Connections carry 95% traffic (rest?)

30. 30 Internet structure: network of networks “Tier-2” ISPs: smaller (often regional) ISPs  Connect to one or more tier-1 ISPs, possibly other tier-2 ISPs France telecome, Tiscali, etc. buys from Sprint Tier 1 ISP Tier-2 ISP Tier-2 ISP pays tier-1 ISP for connectivity to rest of Internet Tier-2 ISPs also peer privately with each other, interconnect at NAP

31. 31 Internet structure: network of networks “Tier-3” ISPs and local ISPs (Time Warner, Earthlink, etc.)  last hop (“access”) network (closest to end systems) Tier 1 ISP Tier-2 ISP local ISP local ISP local ISP local ISP local ISP Tier 3 ISP local ISP local ISP local ISP Local and tier- 3 ISPs are customers of higher tier ISPs connecting them to rest of Internet

32. 32 Internet structure: network of networks a packet passes through many networks!  Local ISP (taxi) -> T1 (bus) -> T2 (domestic) -> T3 (international) Tier 1 ISP Tier-2 ISP local ISP local ISP local ISP local ISP local ISP Tier 3 ISP local ISP local ISP local ISP

33. 33 Organizing the giant structure Networks are complex! many “pieces”:  hosts  routers  links of various media  applications  protocols  hardware, software Question: Is there any hope of organizing structure of network? Or at least our discussion of networks?

34. 34 Turn to analogies in air travel a series of steps ticket (purchase) baggage (check) gates (load) runway takeoff airplane routing ticket (complain) baggage (claim) gates (unload) runway landing airplane routing

35. 35 ticket (purchase) baggage (check) gates (load) runway (takeoff) airplane routing departure airport arrival airport intermediate air-traffic control centers airplane routing ticket (complain) baggage (claim gates (unload) runway (land) airplane routing ticket baggage gate takeoff/landing airplane routing Layering of airline functionality Layers: each layer implements a service  layers communicate with peer layers  rely on services provided by layer below

36. 36 Why layering? Explicit structure allows identification, relationship of complex system’s pieces Modularization eases maintenance, updating of system  change of implementation of layer’s service transparent to rest of system  e.g., runway delay (wheels up time) depends on clearence of destination runway … doesn’t affect rest of system

37. 37 Protocol “Layers” Service of each layer encapsulated Universally agreed services called PROTOCOLS A large part of this course will focus on designing protocols for networking systems

38. 38 Internet protocol stack application: supporting network applications  FTP, SMTP, HTTP, DNS … transport: host-host data transfer  TCP, UDP … network: routing of datagrams from source to destination  IP, BGP, routing protocols … link: data transfer between neighboring network elements  PPP, Ethernet, WiFi, Bluetooth … physical: bits “on the wire”  OFDM, DSSS, CDMA, Coding … application transport network link physical

39. 39 Success of Layering Protocol stack successful in Internet Internet uses wired physical layer links  Very reliable  BER = 10 -8 What about wireless networks  Very unreliable due to channel fluctuations  Due to co-channel interference  Due to external noise Does horizontal layering still hold ?

40. 40 Questions ?

41. 41 message segment datagram frame source application transport network link physical HtHt HnHn HlHl M HtHt HnHn M HtHt M M destination application transport network link physical HtHt HnHn HlHl M HtHt HnHn M HtHt M M network link physical link physical HtHt HnHn HlHl M HtHt HnHn M HtHt HnHn HlHl M HtHt HnHn M HtHt HnHn HlHl M HtHt HnHn HlHl M router switch Encapsulation