Types & Classification of Network

Types of Computer Network

On the basis of network size or structure and the area they are localised in computer networks are classified into three types : –

(1.) Local Area Network(LAN) 

(2.) Metropolitan Area Network(MAN)

(3.) Wide Area Network(WAN)

(1.) Local Area Network(LAN)

Definition

• • LAN is a type of computer network in which several computers are connected properly with each other located within the specific geographical area of diameter 2 km (such as in the same room, on the same floor or in the same building or in the same campus that are connected) to form a single network as to share different computer resources by each one(such as disk drives, printers, data, CPU, fax/modem, applications etc.).

Characteristics/Features

• • Local Area Network is a computer network that spans over a relatively small area. It is confined to small areas i.e., it connects several devices over a distance of 5 to 10 km. 
  • Most LANs are confined to a single building or group of buildings within a campus. However, one LAN can be connected to other LANs over any distance via telephone lines and radio waves.
  • Most LANs connect/use workstations and personal computers.
  • Each node (individual computer) in a LAN has its own CPU which executes its own programs, but it is also able to access data and devices anywhere on the LAN i.e. many users can share data as well as expensive devices, such as laser printers, fax machines etc.
  • Users can also use the LAN to communicate with each other, by sending e-mail or engaging in chat sessions.
  • There are many different types of LANs, Ethernets being the most common and widely used for PCs.
  • The most widely used and dominant LAN type is the Ethernet LAN which is based on the bus topology.
  • LANs are private networks, hence not subject to tariffs or other regulatory controls. For the Wireless LANs, there are additional regulations in several countries.
  • They are the smallest computer network.
  • In LANs data transmission speed is high when compared to the typical WAN (normal 2 to 100 MB /sec or up to 1Gbps latest).
  • It normally uses Bus & Ring topology in their structure.
  • There are different types of Media Access Control methods applied in a LAN to access or share the data in which the common/popular ones are Bus based Ethernet, Token ring etc.
  • LANs are capable of transmitting data at very fast rates i.e. much faster than data can be transmitted over a telephone line but the distances are limited.
  • They use mostly inexpensive equipment.
  • They have low error rates.
  • The transmission speeds in this network is ranging from 10Mbps to 100Mbps. But, now a days 1000 Mbps/more are available.
  • Structures:
    • There are five major components present in a typical LAN:
      i) Basic Network devices – The Nodes, Workstations, printers, file servers which are the basic components of the network and are normally accessed by all other computers of the network.
      ii) Network Communication Devices – These devices are used to connect each basic component of the network. Here, several Intermediate nodes/devices (such as repeaters, bridges and hubs/switches) allow to be connected together to from larger LANs. A LAN may also be connected to another LAN or to WANs and MANs using a Router device.
      iii) Network Interface Cards (NICs) – This hardware device  is required to access the network. It is the interface between the machine and the physical network.
      iv) Cable – This is used as a physical transmission medium. However, present day LAN may not require the physical transmission media. It may be a Wireless LAN.
      v) Network Operating System – This software application is required to control the functioning of network operation and administration.

Advantages

• • It allows sharing of expensive resources among network components such as printers, software and mass storage devices.
  • Comparatively less complex structure hence low set up cost.
  • LAN allows high-speed exchange of essential information.
  • It contributes to increased productivity.

Disadvantages

• • Some type of security system must be implemented if it is important to protect confidential data in LAN.
  • The security may be further low if it is a wireless LAN.
  • LAN is restricted to a small area only.
  • The distances are limited in LAN and there is also a limit on the number of computers that can be attached to a single LAN.

Uses

• • LANs are typically installed in offices, businesses, colleges & universities etc.

(2.) Metropolitan Area Network(MAN)

Definition

• • Metropolitan area networks are large computer network that spans a metropolitan area or a city or a large campus falls between a LAN and WAN up to 5-50 km diameter.
  • A MAN is optimized for a larger geographical area than a LAN, ranging from several blocks of buildings to entire cities.

Characteristics/Features

• • It was developed in 1980s.
  • They are medium size computer network i.e. the network size falls intermediate between LAN and WAN.
  • The typical data transmission speed is in the range of 5- 10 Mbps or more.
  • It normally uses Distributed Queue Dual Bus [DQDB] topology in their structure.
  • This network is normally designed for a city or town.
  • A MAN might be owned and operated by a single organization, but it usually will be used by many individuals and organizations.
  • MANs might also be owned and operated as public utilities or privately owned as per need. 
  • They usually connect several LANs or local networks of the city and forms the MANs.
  • They typically use wireless infrastructure or optical fiber connections to link their sites/components.
  • The common devices used are modem, router and wireless media/cable.

Advantages

• • A MAN often acts as a high speed network to allow sharing of regional resources.
  • It is also frequently used to provide a shared connection to other networks using a link to a WAN.

Disadvantages

• • It is difficult to manage.
  • It is difficult to make the system secure from hackers. 

Uses

• • MANs are typically installed in the city to connect the various LANs branches of an organization, banks, businesses etc.

(3.) Wide Area Network(WAN)

Definition

• • Wide Area Network is the largest network system connecting cities, countries or continents LANs, MANs or WANs using  routers and public communications links and covers whole world/earth.
  • WAN is a network that covers a large geographical area and covers different cities, states and sometimes even countries, is known as WAN.  

Characteristics/Features

• • The largest and most well-known example of a WAN is the Internet.
  • The typical data transmission speed is in the range of 256Kbps- 2 Mbps or more.
  • It normally uses ATM, Frame Relay, Sonet type of topology in their structure.
  • Many WANs are built specific for one particular organization and are private.
  • Many others WANs are built by Internet service providers, provide connections from an organization’s LAN to the Internet.
  • Communication medium used in WANs may be satellite, public telephone networks which are connected by routers.
  • Structures:
    • WANs are often built using Leased lines. At each end of the leased line, a router connects to the LAN on one side and a hub/switch within the WAN on the other. Leased lines can be very expensive.
    • WANs can also be built around public network or Internet.

Advantages

• • It covers the largest geographical area.
  • It is a large place for sharing of software & resources.
  • It distributes workload.

Disadvantages

• • It requires the costliest set up.
  • WAN has more security problems as compare to MAN and LAN.
  • It needs dedicated firewall and antivirus software for security purpose.
  • It has tough troubleshooting. 

Uses

• • WANs are used to connect several LANs, MANs and even WANs together, so that users and computers in one location can communicate with users and computers in other locations.
  • WANs are typically installed anywhere in the world to connect the various LANs/MANs and even WANs branches of same or different organizations, Banks, businesses, Institutions, Government department etc via internet/satellite/public network.