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CS2105

CS2105. Computer Networking I. Ooi Wei Tsang. ooiwt@comp.nus.edu.sg SOC1-04-20. Ong Ghim Hwee. onggh@comp.nus.edu.sg S16-06-10. Emphasis. basic principles and concepts of networking. Not in CS2105.

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CS2105

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  1. CS2105 Computer Networking I

  2. Ooi Wei Tsang ooiwt@comp.nus.edu.sg SOC1-04-20

  3. Ong Ghim Hwee onggh@comp.nus.edu.sg S16-06-10

  4. Emphasis basic principles and concepts of networking

  5. Not in CS2105 router configuration, windows networking, wireless network, video streaming, P2P file sharing, IPv6, security etc.

  6. After CS2105 Advanced Network (3103/3224) Telecomm./E-Comm. (3260/3266) Security (3235/3254)

  7. Continuous Assessment

  8. exams are“semi-open” book one A4-size, double-sided cheat sheet allowed

  9. Expected Workload

  10. "Lighting a Fire, not Filling Buckets" no study notes no “model” answers

  11. Zero Tolerance to Plagiarism

  12. http://www.comp.nus.edu.sg/~cs2105

  13. Today’s Lecture Introduction to networks (Focus on Internet) Five network layers

  14. What is Internet? a network that connects computing devices around the world

  15. Hosts/End Systems

  16. Number of Hosts on the Internet

  17. Hosts rundistributedapplications web: browser, server, proxy bittorrent: client, tracker AIM: client, server :

  18. Applications exchange messages Long messages are broken into packets

  19. Applications communicate usingprotocols “format and order of msgs exchanged, and actions taken after msg are received/sent.”

  20. HTTPFTPSMTPOscar

  21. ApplicationstreatInternetas ablack box

  22. Internet provides two servicesformsg transport

  23. Connection- Oriented Service (TCP) reliable transfer flow control congestion control

  24. Connectionless Service (UDP) simply send

  25. Hosts are connected through intermediate packet switches

  26. “store-and-forward” principle

  27. Internet is apacket switchingnetwork

  28. circuit switching resources are reserved, guranteeing services.

  29. packet switching resources consumed on-demand, best-effort service

  30. packet switching is more efficient why?

  31. Network Taxanomy Telecommunication Networks Circuit Switched Packet Switched Datagram Network Virtual Circuit Network

  32. Internet is a datagram network forwarding decision is done based on dest address

  33. virtual circuit network forwarding based on path which is established and maintained per connection

  34. Delay in packet switching • For each link in the path • packets get transmitted onto a link as bits • bits propagate to next router • router stores and process packet • packet wait to be transmitted

  35. Delay in packet switching • Transmission Delay • Propagation Delay • Processing Delay • Queueing Delay

  36. Internet is a“network of networks” A hierarchy of ISPs (Tier 1, 2, 3), each owns routers and links

  37. traceroute demo

  38. node-to-node communications Ethernet, PPP

  39. physical medium twisted pair copper wire coaxial cable radio channels fiber optics

  40. Internet is complex applications, wires, routing, packets, protocols, access technologies …

  41. Divide into layers simple interfaces between layers hide details of one layer from another

  42. ApplicationTransportNetworkLinkPhysical

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