Class 12: Networking Set 4

What is a computer network? Give Advantages of Network.

A computer network consists of two or more computers that are linked in order to share resources such as printers and CD-ROMs, exchange files, or allow electronic communications. The computers on a computer network may be linked through cables, telephone lines, radio waves, satellites, or infrared light beams.

It is possible to connect various types of devices to a network:

• Desktop computers.
• Laptops.
• Printers
• Scanners
• Personal digital assistants (PDA).
• Smartphones.
• Print and file servers.

A network can share many types of resources:

• Services, such as printing or scanning.
• Applications, such as databases.
• Storage space on removable devices, such as hard drives or optical drives.

Networks can be used to access information stored on other computers, print documents using shared printers, and synchronize the calendar between your computer and your smartphone.

Network devices connect through various connections:

• Copper wiring: uses electrical signals to transmit data between devices.
• Fiber optic cabling: uses plastic or glass cable, also called fiber, to transport information as the light emitted.
• Wireless connection: uses radio signals, infrared (laser) technology, or satellite transmissions.

Networking benefits
The benefits of networking on computers and other devices include low costs and higher productivity. Thanks to networks, resource scan be shared, which reduces data duplication and corruption.

Fewer peripherals are needed.
Every computer on the network does not need its printer, scanner, or backup device. It is possible to configure several printers in a central location and share them among network users. All network users send print jobs to a central print server that manages printr equests. The print server can distribute print jobs among the various printers, or it can queue jobs that require a particular printer.

Greater communication capabilities
Networks offer various collaboration tools that can be used to establish communications between network users. Online collaboration tools include email, forums and chat, voice and video, and instant messaging. With these tools, users can communicate with friends,family, and colleagues.

Duplication and file corruption are avoided
A server manages network resources. The servers store the data and share it with the users of a network. Confidential or essential data can be protected and shared with users who have permission to access such data. Document tracking software can be used toprevent users from overwriting or modifying files that other users are accessing at the same time.

Lower cost in license acquisition
Acquiring application licenses can be expensive for individual computers. Many software providers offer site licenses for networks,which can significantly reduce the cost of the software. The site license allows a group of people or an entire organization to usethe application for a single fee.

Centralized administration
Centralized administration reduces the number of people needed to manage devices and data on the network, allowing the company to save time and money.

Individual users of the network do not need to manage their data and devices. An administrator can control the data, devices, and permissions of network users. Creating backup copies of the data is more comfortable because of the data stored in a central location.

Resources are conserved
It is possible to distribute data processing among many computers to prevent a computer from being overloaded with processing tasks.

What are the different types of networks?

Networks can be classified into three categories:

A local area network (LAN) is a collection of devices connected together in one physical location, such as a building, office, or home. A LAN can be small or large, ranging from a home network with one user to an enterprise network with thousands of users and devices in an office or school.

Regardless of size, a LAN’s single defining characteristic is that it connects devices that are in a single, limited area. In contrast, a wide area network (WAN) or metropolitan area network (MAN) covers larger geographic areas. Some WANs and MANs connect many LANs together.


MAN or Metropolitan area Network covers a larger area than that of a LAN and smaller area as compared to WAN. It connects two or more computers that are apart but resides in the same or different cities. It covers a large geographical area and may serve as an ISP (Internet Service Provider). MAN is designed for customers who need a high-speed connectivity. Speeds of MAN ranges in terms of Mbps. It’s hard to design and maintain a Metropolitan Area Network.

WAN or Wide Area Network is a computer network that extends over a large geographical area, although it might be confined within the bounds of a state or country. A WAN could be a connection of LAN connecting to other LAN’s via telephone lines and radio waves and may be limited to an enterprise (a corporation or an organization) or accessible to the public. The technology is high speed and relatively expensive.

What are the communication channels? What choices do you have which choosing a communication channel for a network?

The cable is a physical media, through which an analog and digital data transfer take place. While selecting the cable, a type of data transfer, purpose, advantages, and disadvantages taken into consideration.

Types of Cables
Cables are classified as

Twisted pair
Optical fiber

Twisted pair

Twisted pair cables consist of color-coded pairs of insulated copper wires, one wire carries the signal, and the other is used for ground reference. Every two wires are twisted around each other to form pairs that are encased in a plastic sheath each wire with a diameter of 0.4 mm to 0.8 mm.

The number of pairs varies depending on the cable type. More twists per foot in a pair of wires, less the cross talk.

The significance of twisting is it reduces or nullifies the interference such as noise or cross talk caused due to radiofrequency of electromagnetic interference.

By twisting the wires, the effect of noise or disturbance is the same on both wires. Since the receiver takes only the difference between the two wires the effective noise is canceled.

Twisted pair cables are two types.

Shielded Twisted cable (STP)
Unshielded Twisted pair cable (UTP).

Coaxial Cable

Coaxial cables are also called coax (short form).

Coaxial cable is a type of cable with multiple layers.

Coaxial cables have an inner conductor is called the core, which carries the radio frequency signal. The core wire may be a single solid conductor or multi strands of twisted cable. It is surrounded by a dielectric insulator.

The dielectric insulator separates the inner conductor and outer copper braided mesh. The dielectric insulator is covered by copper mesh (foil or braided conductor). The dielectric insulator may be polyethylene foam or PTFE which minimizes ohmic losses arising from contact with the conductors. Outer jacket is to protect the cable from environmental and mechanical damages. A common choice is PVC.

Optical Fiber Cable

It also is known as fiber optic cable consists of strands of one or more fibers inside the casing and its assembly is similar to electrical cable.

Optical fiber has three parts

It is the inner layer is called the core, with refractive index n1. Light is guided in this part. The core will have a higher refractive index than cladding.

which surrounds the core, with refractive index n2. Whose refractive index is less than the core? The purpose of cladding is to keep the light reflections in core instead of being reflections.

Which is an outer layer for protecting the cable from damages.

There are two types of optical fibers, glass, and plastic. Plastic fiber is used for short communication. Optical fiber transfers data at the speed of light in the glass.

Optical fiber cable uses light pulses instead of electrical pulses to transmit data. The potential hazard of Infrared red light used in telecommunications cannot be seen by the naked eye.

Optical fiber cable comes in single-mode or multimode connections.