Network Classification.

Computer networks are typically classified by scale, ranging from small, personal networks to global wide-area networks and the Internet itself. The following readings provide detailed information on the common network classifications.

Personal Area Networks

• Personal Area Network is a network arranged within an individual person, typically within a range of 10 meters.

• Personal Area Network is used for connecting the computer devices of personal use is known as Personal Area Network.
• Thomas Zimmerman was the first research scientist to bring the idea of the Personal Area Network.
• Personal Area Network covers an area of 30 feet.
• Personal computer devices that are used to develop the personal area network are the laptop, mobile phones, media player, and play stations.

Local Area Networks

• Local Area Network is a group of computers connected to each other in a small area such as a building, office.

• LAN is used for connecting two or more personal computers through a communication medium such as twisted pair, coaxial cable, etc.
• It is less costly as it is built with inexpensive hardware such as hubs, network adapters, and ethernet cables.
• The data is transferred at an extremely faster rate in Local Area Network.
• Local Area Network provides higher security.

Metropolitan Area Networks

• A metropolitan area network is a network that covers a larger geographic area by interconnecting a different LAN to form a larger network.

• Government agencies use MAN to connect to the citizens and private industries.
• In MAN, various LANs are connected to each other through a telephone exchange line.
• The most widely used protocols in MAN are RS-232, Frame Relay, ATM, ISDN, OC-3, ADSL, etc.
• It has a higher range than Local Area Network(LAN).

Wide Area Networks

• A Wide Area Network is a network that extends over a large geographical area such as states or countries.

• A Wide Area Network is quite a bigger network than a LAN.
• A Wide Area Network is not limited to a single location, but it spans over a large geographical area through a telephone line, fiber optic cable, or satellite links.
• The internet is one of the biggest WAN in the world.
• A Wide Area Network is widely used in the field of Business, government, and education.

Network Topologies

Network topology is the arrangement of the elements of a communication network. Network topology can be used to define or describe the arrangement of various types of telecommunication networks, including command and control radio networks, industrial field busses, and computer networks.

Types of Topology

Mesh Topology

In a mesh topology, each device is connected to every other device on the network through a dedicated point-to-point link. When we say dedicated it means that the link only carries data for the two connected devices only. Let's say we have n devices in the network then each device must be connected with (n-1) devices of the network. A number of links in a mesh topology of n devices would be n(n-1)/2.

Advantages of Mesh topology

1. No data traffic issues as there is a dedicated link between two devices which means the link is only available for those two devices.
2. Mesh topology is reliable and robust as a failure of one link doesn’t affect other links and the communication between other devices on the network.
3. Mesh topology is secure because there is a point-to-point link thus unauthorized access is not possible.
4. Fault detection is easy.

Disadvantages of Mesh topology

1. Amount of wires required to connected each system is tedious and a headache.
2. Since each device needs to be connected with other devices, the number of I/O ports required must be huge.
3. Scalability issues because a device cannot be connected with a large number of devices with a dedicated point-to-point link.

Star Topology

In star topology, each device in the network is connected to a central device called a hub. Unlike Mesh topology, star topology doesn’t allow direct communication between devices, a device must have to communicate through the hub. If one device wants to send data to another device, it has to first send the data to the hub and then the hub transmits that data to the designated device.

Advantages of Star topology

1. Less expensive because each device only needs one I/O port and needs to be connected with a hub with one link.
2. Easier to install
3. Less amount of cables required because each device needs to be connected to the hub only.
4. Robust, if one link fails, other links will work just fine.
5. Easy fault detection because the link can be easily identified.

Disadvantages of Star topology

1. If the hub goes down everything goes down, none of the devices can work without a hub.
2. Hub requires more resources and regular maintenance because it is the central system of star topology.

Bus Topology

In a bus topology, there is the main cable and all the devices are connected to this main cable through drop lines. There is a device called tap that connects the drop line to the main cable. Since all the data is transmitted over the main cable, there is a limit of drop lines and the distance the main cable can have.

Advantages of bus topology

1. For easy installation, each cable needs to be connected with the backbone cable.
2. Fewer cables required than Mesh and star topology

Disadvantages of bus topology

1. Difficultly in fault detection.
2. Not scalable as there is a limit of how many nodes you can connect with backbone cable.

Ring Topology

In a ring topology, each device is connected with the two devices on either side of it. There are two dedicated point-to-point links a device has with the devices on either side of it. This structure forms a ring thus it is known as a ring topology. If a device wants to send data to another device then it sends the data in one direction, each device in ring topology has a repeater, if the received data is intended for another device then the repeater forwards this data until the intended device receives it.

Advantages of Ring Topology

1. Easy to install.
2. Managing is easier as to add or remove a device from the topology only two links are required to be changed.

Disadvantages of Ring Topology

1. A link failure can fail the entire network as the signal will not travel forward due to failure.
2. Data traffic issues, since all the data is circulating in a ring.

Network Architecture

Computer Network Architecture is defined as the physical and logical design of the software, hardware, protocols, and media of the transmission of data. Simply we can say that how computers are organized and how tasks are allocated to the computer.

Two of the most widely used types of network architecture are,

○ peer-to-peer architecture

○ client/server architecture

Peer-to-peer architecture

In peer-to-peer architecture, tasks are allocated to every device on the network. There is no real hierarchy in this network, all computers are considered equal and all have the same abilities to use the resources available on this network. Instead of having a central server that would act as the shared drive, each computer that connected to this network would act as the server for the files stored on it.

Advantages Of Peer-To-Peer Network:

• It is less costly as it does not contain any dedicated server.
• If one computer stops working but, other computers will not stop working.
• It is easy to set up and maintain as each computer manages itself.

Disadvantages Of Peer-To-Peer Network:

• In the case of the Peer-To-Peer network, it does not contain a centralized system. Therefore, it cannot back up the data as the data is different in different locations.
• It has a security issue as the device is managed itself.

Client/server architecture

End users called clients to access the resources such as songs, videos, etc. from a central computer known as Server. The central controller is known as a server while all other computers/devices in the network are called clients. A server performs all the major operations such as security and network management. A server is responsible for managing all the resources such as files, directories, printers, etc. All the clients communicate with each other through a server.

Advantages Of Client/Server network:

• A Client/Server network contains the centralized system. Therefore we can back up the data easily.
• A Client/Server network has a dedicated server that improves the overall performance of the whole system.
• Security is better in the Client/Server network as a single server administers the shared resources.
• It also increases the speed of the sharing of resources.

Disadvantages Of Client/Server network:

• Client/Server network is expensive as it requires a server with large memory.
• A server has a Network Operating System(NOS) to provide the resources to the clients, but the cost of NOS is very high.
• It requires a dedicated network administrator to manage all the resources.