Introduction to Computer Networks

Data Communication

This sharing can be local or remote. Between individuals, local communication usually occurs face to face, while remote communication takes place over distance.

Message

The message is the information (data) to be communicated. Popular forms of information include text, numbers, pictures, audio, and video.

Sender

Is the device that sends the data message. It can be a computer, workstation, telephone handset, video camera, and so on.

Receiver

The receiver is the device that receives the message. It can be a computer, workstation, telephone handset, television, and so on.

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

Protocol

is a set of rules that govern data communications. It represents an agreement between the communicating devices.

Network

A set of devices (often referred to as nodes) connected by communication links.

Distributed Processing

Most networks use distributed processing, in which a task is divided among multiple computers. This approach enhances efficiency and resource sharing, allowing for faster data processing and improved performance.

Network Criteria

A network must be able to meet a certain number of criteria. The most important of these are performance, reliability, and security.

Performance

can be measured in many ways, including transit time and response

time.

Reliability

In addition to accuracy of delivery, network reliability is measured by the frequency of failure, the time it takes a link to recover from a failure, and the network's robustness in a catastrophe.

Security

Network security issues include protecting data from unauthorized access, protecting data from damage and development, and implementing policies and procedures for recovery from breaches and data losses.

Point-to-point connection

provides a dedicated link between two devices. The entire capacity of the link is reserved for transmission between those two devices.

Multipoint connection

is one in which more than two specific devices share a single link.

Physical Topology

refers to the way in which a network is laid out physically. One or more devices connect to a link; two or more links form a topology.

Mesh topology

The term dedicated means that the link carries traffic only between the two devices it connects.

Star Topology

each device has a dedicated point-to-point link only to a central controller, usually called a hub. The devices are not directly linked to one another.

Local Area Networks

generally called LANs, are privately-owned networks within a single building or campus of up to a few kilometres in size.

Metropolitan Area Network

This system grew from earlier community antenna systems used in areas with poor over-the-air television reception. In these early systems, a large antenna was placed on top of a nearby hill and signal was then piped to the subscribers' houses.

Wide Area Network

It contains a collection of machines intended for running user (i.e., application) programs.

Internet

It has affected the way we do business as well as the way we spend our leisure time.