Computer Networks 1DV201 1
Link to coursepage http://w3.msi.vxu.se/users/ofl/1dv201/index.html 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) Email 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 Java) 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 But also other types of networks like dedicated networks in cars and houses 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: www.netbook.cs.purdue.edu application: ftp Network protocols require binary values Library routines exist to translate from names to numbers 21
Figure 2.1 Sending a letter
Figure 2.3 Peer-to-peer processes
Figure 2.4 model An exchange using the Internet
Figure 1.1 Five components of data communication
Figure 1.2 Simplex
Figure 1.3 Half-duplex
Figure 1.4 Full-duplex
Figure 1.7 Categories of topology
Figure 1.8 Fully connected mesh topology (for five devices)
Figure 1.9 Star topology
Figure 1.10 Bus topology
Figure 1.11 Ring topology
Figure 1.14 MAN
Figure 1.15 WAN
Figure 1.16 Internet today
Example API 37
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 38
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 39
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 40
Example Code Using API: Echoserver 41
Echoserver (2 of 2) Actually works on the Internet API calls replace conventional I/O No networking knowledge required 42
Example Code Using API: Webserver 43
Webserver (2 of 6) 44
Webserver (3 of 6) 45
Webserver (4 of 6) 46
Webserver (5 of 6) 47
Webserver (6 of 6) 48
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 49
Summary (continued) Computer networks Deliver data from source to destination Automatically find optimal paths Handle problems that occur We will learn how 50