1. 1 Computer Networks DA2402

2. 2 Chapter 1-3 Introduction

3. 3 Topic and Scope  Computer networks and internets: an overview of concepts, terminology, and technologies that form the basis for digital communication in private corporate networks and the global Internet.

4. 4 You Will Learn  Terminology  Communication basics  Media and signals  Asynchronous and synchronous communication  Relationships among bandwidth, throughput, and noise  Frequency-division and time-division multiplexing

5. 5 You Will Learn (continued)  Networking and network technologies  Packet switching  Framing, parity, and error detection  Local and wide area technologies  Network addressing  Connection and extension (repeaters, bridges, hubs, switches)  Topologies and wiring (star, ring, bus)  Next-hop forwarding  Shortest path computation  Measures of delay and throughput  Protocol layers

6. 6 You Will Learn (continued)  Internets and Internetworking  Motivation and concept  Internet Protocol (IP) datagram format and addressing  Internet routers and routing  Address binding (ARP)  Internet control messages (ICMP)  User Datagram Protocol (UDP)  Transmission Control Protocol (TCP)  Protocol ports and demultiplexing

7. 7 You Will Learn (continued)  Network applications  Client-server paradigm  Domain name system (DNS)  File transfer (FTP)  Remote login (TELNET)  Email transfer (SMTP)

8. 8 What You Will NOT Learn  Commercial aspects  Products  Vendors  Prices  Network operating systems  How to purchase/configure/operate

9. 9 Background Required  Ability to program (in Java)  Familiarity with basic tools  Text editor  Compiler / linker / loader

10. 10 Background Required (continued)  Basic knowledge of operating systems  Terminology  Functionality  Processes and concurrent processing  Desire to learn

11. 11 Motivation for Networking  Information access  Interaction among cooperative application programs  Resource sharing

12. 12 Practical Results  Email  File transfer / access  Web browsing  Remote login / execution  The Internet

13. 13 What a Network Includes  Transmission hardware  Special-purpose hardware devices  Interconnect transmission media  Control transmission  Run protocol software  Protocol software  Encodes and formats data  Detects and corrects problems

14. 14 What a Network Does  Provides communication that is  Reliable  Fair  Efficient  From one application to another

15. 15 What a Network Does (continued)  Automatically detects and corrects  Data corruption  Data loss  Duplication  Out-of-order delivery  Automatically finds optimal path from source to destination

16. 16 Network Programming  Network allows arbitrary applications to communicate  Programmer does not need to understand network technologies  Network facilities are accessed through an Application Program Interface

17. 17 Basic Paradigm for Internet Communication  Establish contact  Exchange data (bi-directional)  Terminate contact

18. 18 Establishing Contact  Performed by pair of applications  One application waits for contact (called server )  Other application initiates contact (called client )

19. 19 Identifying a Waiting Application  Conceptually two items specified  Computer  Application on that computer  Terminology  Computer identified by domain name  Application identified by program name

20. 20 Representations and Translations  Humans use names such as  computer: www.netbook.cs.purdue.edu  application: ftp  Network protocols require binary values  Library routines exist to translate from names to numbers

21. 21 Example API

22. 22 Example #1: Echo  Useful for network testing  Server returns exact copy of data sent  User on computer X runs echoserver 22000  User on another computer runs echoclient X 22000

23. 23 Example #2: Chat  Miniature version of Internet chat service  Allows two users to communicate  User on computer X runs chatserver 25000  User on another computer runs chatclient X 25000

24. 24 Example Application: Web Server  User on computer X runs webserver 27000  User on another computer runs browser and enters URL: http://X:27000/index.html

25. 25 Example Code Using API: Echoserver

26. 26 Echoserver (2 of 2)  Actually works on the Internet  API calls replace conventional I/O  No networking knowledge required

27. 27 Example Code Using API: Webserver

28. 28 Webserver (2 of 6)

29. 29 Webserver (3 of 6)

30. 30 Webserver (4 of 6)

31. 31 Webserver (5 of 6)

32. 32 Webserver (6 of 6)

33. 33 Summary  Studying networks is important because  The world is interconnected  Applications now operate in a distributed environment  This course  Covers networking and internetworking  Explains the mystery  Will be hard work

34. 34 Summary (continued)  Computer networks  Deliver data from source to destination  Automatically find optimal paths  Handle problems that occur  We will learn how