1. Computer Networks DA2402

2. Chapter 1-3
Introduction

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

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

9. Background Required Ability to program in C
Knowledge of low-level programming constructs
Familiarity with basic tools
Text editor
Compiler / linker / loader

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

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

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

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

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

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

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. Representations and Translations
Humans use names such as
computer:
application: ftp
Network protocols require binary values
Library routines exist to translate from names to numbers

21. Example API

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. 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. Example Application: Web Server
User on computer X runs
webserver 27000
User on another computer runs browser and enters URL:

25. Example Code Using API: Echoserver

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

27. Example Code Using API: Webserver

28. Webserver (2 of 6)

29. Webserver (3 of 6)

30. Webserver (4 of 6)

31. Webserver (5 of 6)

32. Webserver (6 of 6)

33. Summary Studying networks is important because This course
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. Summary (continued) Computer networks We will learn how
Deliver data from source to destination
Automatically find optimal paths
Handle problems that occur
We will learn how