Data Communication and Computer Networks: Components, Characteristics, and Topologies, Lecture notes of Computer Networks

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Computer Networks

M. Bilal Khan Lecturer CS & IT Superior University, Lahore [email protected]

Objectives

 (^) Course Module Discussion  (^) Data Communication  (^) Network vs Internet  (^) internet, Intranet, Extranet

DATA COMMUNICATION

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

Effectiveness of Data Comm. System

 (^) Effectiveness depends upon four fundamental characteristics

1. Delivery : The system must deliver data to correct destination. Data received by the indented user only
2. Accuracy: The system must deliver data accurately (no change).  (^) Data changed & uncorrected is unusable
3. Timeliness: The system must deliver data in timely manner  (^) Data arrived late are useless  (^) In the same order (video and audio) & without delay (Real time transmission)
4. Jitter: Variation in the packet arrival time (uneven quality in the video is the result)

Components

1. Message: the information (data) to be communicated  (^) Consist of text, numbers, pictures, audio, or video
2. Sender: the device that sends the data message  (^) Computer, workstation, telephone handset, video camera, …
3. Receiver: the device that receives the message  (^) Computer, workstation, telephone handset, television, ….

Components

4. Medium: The physical path by which a message travels from sender to receiver  (^) twisted pair, coaxial cable, fiber-optic, radio waves

Data Representation

Text Audio Video Numbers Images

Data Flow

 (^) Communication between two devices can be:  Simplex  Half-Duplex  Full-Duplex

Data Flow

 Half-Duplex (one-lane with two-directional traffic)  Each station can both transmit and receive, but not at the same time  When one device is sending, the other can only receive, and vice versa  The entire capacity of a channel is taken over by the transmitting device  Example: Walkie-talkies Data Data

Data Flow

 Full-Duplex (Duplex) (two-way street)  Both stations can transmit and receive at same time  (^) Signals going in either direction sharing the capacity of the link  Sharing can occur in two ways:  (^) Link has two physically separate transmission paths  (^) One for sending and the other for receiving  (^) The capacity of the channel is divided between signals travelling in both directions  Example: Telephone network Data Data

Network

• (^) Network Performance
• (^) Characteristics of a Network
• (^) Physical Structures

 (^) Α NETWORK is simply defined as something that connects things together for a specific purpose.  (^) The term network is used in a variety of contexts, including telephone, television, computer, or even people networks.  (^) A COMPUTER NETWORK connects two or more devices together to share information and services, including  (^) Websites  (^) Email and messaging

What is a Network?

Characteristics of a Network

 (^) Performance  (^) Performance is evaluated by two contradictory networking metrics:  (^) Throughput (high): a measure of how fast we can actually send data through a network  (^) Delay (low)

Terminology

 (^) 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