Computer Network of Computer Science, Study Guides, Projects, Research of Computer Networks

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Program Name :B.Tech

Semester :ECE 6th Sem

Course Name: Computer Network

Course Code:EC 602

Facilitator Name: Megha Dewan

Topic Name:- Introduction to Computer Network

 Contents of Topic: Behrouz A. Forouzan  Learning Outcome: Students get to know about basics of Computer Network UNIT No. 1

Components of a data communication system

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.

1. Message. The message is the information (data) to be communicated. Popular forms of information include text, numbers, pictures, audio, and video. 2. Sender. The sender is the device that sends the data message. It can be a computer, telephone handset, video camera, and so on. 3. Receiver. The receiver is the device that receives the message.It can be a computer, telephone handset, television, and so on. 4.Transmission medium. The transmission medium is the physical path by which a message travels from sender to receiver. Some examples of transmission media include twisted- pair wire, coaxial cable, fiber-optic cable, and radio waves. 5.Protocol. A protocol is a set of rules that govern data communications. It represents an agreement between the communicating devices. Without a protocol, two devices may be connected but not communicating. just as a person speaking French cannot be understood by a person who speaks only Japanese.

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

Simplex:

In simplex mode, the communication is unidirectional, as on a one- way street. Only one of the two devices on a link can transmit; the other can only receive. Examples :- Keyboards and traditional monitors are examples of simplex devices. The keyboard can only introduce input; the monitor can only accept output. The simplex mode can use the entire capacity of the channel to

send data in one direction.

Full-Duplex:

In full-duplex both stations can transmit and receive simultaneously. The full- duplex mode is like a two-way street with traffic flowing in both directions at the same time. In full-duplex mode, signals going in one direction share the capacity of the link: with signals going in the other direction. Example :- full-duplex communication is the telephone network. When two people are communicating by a telephone line, both can talk and listen at the same time. The full-duplex mode is used when communication in both directions is required all the time. The capacity of the channel, however, must be divided between the two directions.

COMPUTER NETWORKS

Computer network consists of two or more computers that are linked in order to share resources, exchange data files or to allow electronic communication. The computers on a network may be linked through cables, telephone lines, radio waves, satellites or infrared light beams. There are two aspects of computer networks – hardware and software. Hardware includes physical connection between two machines by using adaptors, cables, routers, bridges etc. software includes a set of protocols. Protocols define a formal language among various components. It makes hardware usable by applications.

A fully connected mesh topology (five devices)

• In mesh topology every device has a dedicated point-to-point link to every other device.
  • The link carries traffic only between the two devices it connects.
  • Duplex-mode
  • Advantages: Guaranteed dedicated links eliminates traffic problems privacy and security this makes fault identification easy
  • Disadvantages: Cabling and number of IO ports required wiring is greater than available space hardware is required for each link – expensive

A star topology connecting four stations

• In star topology, each device has a dedicated point-to-point link only to a central controller called hub.
• The controller acts as an exchange: if one device wants to send data to another , it sends the data to controller, which then relays the data to the another connected device.
  • Advantages: 1.less expensive
  2. Robustness – if one link fails, only that link is affected, other links remain active.
  • Disadvantages: Dependency of the whole topology on one single point. Star requires less than mesh, each node is linked to the hub. So more cabling is required.

A ring topology connecting six stations

• In ring topology each device has a point-to-point connection with only the two devices on either side of it.
• A signal is passed along a ring in one direction, from device to device until it reaches its destination.
• Advantages: Easy to install and reconfigure
• To add or delete a device requires changing only two connections. The only constraints are media and traffic.
• Disadvantages; unidirectional
• A break in a ring can disable the entire network

A hybrid topology: a star backbone with three bus networks

Business Applications of Networks

• Resource sharing
  • (^) High reliability
  • (^) Saving money
  • (^) Scalability Client-server model

Business Applications of Networks

• (^) The client-server model involves requests and replies.