Computer Communication Computer Communication & Networks& Networks

Lecture # 01Introduction

Grading PolicyGrading Policy Final Exam: 40% Mid term Exam 20% Assignments 10% Quizzes: 10% Labs + Project 20%

ReadingReading Text book:

Data Communications and Networking, 4/e B.A. Forouzan, McGraw-Hill, 2003,

ISBN 0-07-292354-7. Data and Computer Communication by William

Stallings (7th Edition) Prentice Hall. Reference books:

Computer Networking, a top-down approach featuring the Internet (3rd edition), J.K.Kurose, K.W.Ross,Addison-Wesley, 2005,

ISBN 0-321-26976-4.

Data CommunicationsData CommunicationsThe term term telecommunicationtelecommunication

means communication at a means communication at a distance. The word distance. The word datadata refers to refers to information presented in whatever information presented in whatever form is agreed upon by the parties form is agreed upon by the parties creating and using the data. creating and using the data. Data Data communicationscommunications are the exchange are the exchange of data between two devices via of data between two devices via some form of transmission medium some form of transmission medium such as a wire cable. such as a wire cable.

Fundamental Fundamental CharacteristicsCharacteristicsThe effectiveness of a data

communication system depend on four fundamental characteristics:◦Delivery◦Accuracy◦Timelines◦Jitter

Five Components of Data Five Components of Data CommunicationCommunication

1. Message

2. Sender

3. Receiver

4. Medium

5. Protocol

Data RepresentationData Representation

Information comes in different form such as,

• Text • Numbers• Images• Audio• Video

Figure 1.2 Figure 1.2 Data flow (simplex, half-duplex, Data flow (simplex, half-duplex, and full-duplex)and full-duplex)

Simplex

Half Duplex

Full Duplex

1-2 NETWORKS1-2 NETWORKSA A networknetwork is a set of devices (often is a set of devices (often

referred to as referred to as nodesnodes) connected by ) connected by communication communication linkslinks. A node can be a . A node can be a computer, printer, or any other device computer, printer, or any other device capable of sending and/or receiving data capable of sending and/or receiving data generated by other nodes on the network.generated by other nodes on the network.

Networks: key issuesNetworks: key issues Network criteria

◦ Performance Transit time Throughput Delay

◦ Reliability Data transmitted are identical to data received. Measured by the frequency of failure The time it takes a link to recover from a failure

◦ Security Protecting data from unauthorized access

TerminologyTerminology

The throughput or bandwidth of a channel is the number of bits it can transfer per second

The latency or delay of a channel is the time that elapses between sending information and the earliest possible reception of it

Figure 1.3 Figure 1.3 Types of connections: point-to-Types of connections: point-to-point and multipointpoint and multipoint

Network topologiesNetwork topologiesTopology defines the way hosts

are connected to the network

Network topology issuesNetwork topology issues

1. high throughput (bandwidth)

2. low latency

A goal of any topology

Categories of TopologyCategories of Topology

Figure 1.5 Figure 1.5 A fully connected mesh topology A fully connected mesh topology (five devices)(five devices)

Advantages & disadvantages Advantages & disadvantages of mesh topologyof mesh topology

Advantages - Dedicated links eliminate the traffic

problem -Secure communication -Ease of fault identification & fault

Isolation -Robust Disadvantages-Large number I/O ports & cabling

required-Installation & reconfiguration is difficult-Wiring can be greater than available

space-Expensive

Figure 1.6 Figure 1.6 A star topology connecting four A star topology connecting four stationsstations

Advantages & disadvantages Advantages & disadvantages of star topologyof star topology Advantages -Less expensive than mesh topology -Installation & reconfiguration are easy -Robust - Ease of fault identification & fault Isolation-Required less cabling than mesh topology Disadvantages-Dependency of whole topology on single pointApplication: High Speed LAN

Figure 1.7 Figure 1.7 A bus topology connecting three A bus topology connecting three stationsstations

Advantages & disadvantages Advantages & disadvantages of bus topologyof bus topologyAdvantages -Ease of installation -Required less cablingDisadvantages -Difficult reconnection &fault isolation -A fault or break stops all

transmission

Figure 1.8 Figure 1.8 A ring topology connecting six A ring topology connecting six stationsstations

Advantages & disadvantages Advantages & disadvantages of bus topologyof bus topology Advantages-Ease of installation & reconfiguration

Disadvantages-A break in ring can disable the entire

link

A hybrid topology: a star backbone with three A hybrid topology: a star backbone with three bus networksbus networks

Categories of networks: LAN, Categories of networks: LAN, MAN, WANMAN, WAN

Network in small geographical Area (Room, Building or a Campus) is called LAN (Local Area Network)

Most common LAN topologies are bus, ring &star Network in a City is call MAN (Metropolitan

Area Network)

Network spread geographically (Country or across Globe) is called WAN (Wide Area Network)

Figure 1.11 Figure 1.11 WANs: a switched WAN and a WANs: a switched WAN and a point-to-point WANpoint-to-point WAN

Figure 1.12 Figure 1.12 A heterogeneous network made A heterogeneous network made of four WANs and two LANsof four WANs and two LANs

1-3 THE INTERNET1-3 THE INTERNET

The The InternetInternet has revolutionized many has revolutionized many aspects of our daily lives. It has affected aspects of our daily lives. It has affected the way we do business as well as the way the way we do business as well as the way we spend our leisure time. The Internet is we spend our leisure time. The Internet is a communication system that has brought a communication system that has brought a wealth of information to our fingertips a wealth of information to our fingertips and organized it for our useand organized it for our use

1.29

Figure 1.13 Hierarchical organization of the Internet

ProtocolProtocolA protocol is a set of rules that

governs data communication key elements of protocol are

Syntax Semantics Timing

StandardsStandardsStandards are agreed upon rules,

which Provide guideline to manufacturer, venders, governments agencies & other service providers to ensure the interconnectivity.

Data communication fall into two categories

-De facto -De Jure

ApplicationsApplications E-mail Searchable Data (Web Sites) News Groups Internet Telephony (VoIP) Video Conferencing Chat Groups Internet Radio