Types pf computer Network

NETWORKS

Today almost 80 percent of the businesses are connected to a network or the internet. Most of us are aware of the facilities provided by the network and if not then we need to know, as we all will need to know it today or tomorrow. We might think that where did the networks come from or did it emerged on it's own as a unique or independent technology. But the answer to this is No ; the roots of networking came from the early communication techniques like telegraph and telephone. Network does not work by connecting the computers, but there are lots of other things which have to be taken care of, while networking. We have to also know about the hardware and software which helps to create the network. So let's see all these in details in the coming section.

What is Network?

We can refer to networking as the art and science of connecting computers through network cables which helps to communicate. The concept of network is new but is based on the Victorian-era invention: the telegraph, telephone and teletypewriter. Data communication is the objective of network, which is the electronic format of communication. The data is conveyed with the use of on-and-off pulses of electricity. It is quite interesting to know that all these modern techniques are based on the old and familiar concepts. Although we might have no idea of network but we all would have used it in some way. I think we all have played as a child the game using two cups tied with the string and we tried to speak from one end to our friend on the other end. So that means we all have used network since we were kids. Let's now understand the meaning of the network in the computing terms.

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Network is a group of computers and other peripheral devices. All the computers and the other devices on the network can communicate to each, other then that they can also share the resources like printers, server and the extra storage space. Network helps to share Data, Application and Peripherals. The network is not just connection of two computers but much more then that. There are number of hardware and software which make all these possible. Basic components of the network are listed and explained further. After we discuss about the components required for the network we will also look at different types of network like Local Area Network, Backbone Network, Metropolitan Area Network and Wide Area Network.

Types of Networks

Networks can be categorized in many different methods but the most common way is to have a look at the geographical scopes of the network. Each of the network have geographical limitations. The most common types of networks are Local Area Network (LAN), Backbone Network (BN), Metropolitan Area Network (MAN) and Wide Area Network (WAN). They are classified on the basis of the geographical limitations. They are different from one another as each of them has different purpose and they also use different techniques of communication. The report will give a brief idea on their suitability to the type and situation of the business so as to install a successful network.

LOCAL AREA NETWORK (LAN)

A local area network (LAN) is a group of computers and associated devices that share a common communication line or wireless link. It also shares the resources from the single server within a small geographical area like small office building, school, university campus etc. LAN is the data communication system that lies within a very small geographical area. In the LAN the server stores most of the applications and the data which are used by n number of users. Where n are number of user which can be as les as two to three and further can be added up to thousands by selecting special type of LAN.

LANs can be further classified depending on the type of protocol used by them. Protocol is a set of rules that governs the communication between computers on the network. The rules include the guidelines that regulate some characteristics of the network like, selection of physical topology, types of cables used, transfer speed and the method of accessing the resources and data on the network. So depending on the protocol LAN can be divided into following types:

Components required for LAN

There are five basic components for the network. The first two are the computers on the two ends of communication client computer and the server (not in case of peer-to-peer networks). Other components are: Network Interface Card (NIC), Network cables and Hubs and Network Operating System (NOS). All these are equally important for successful installation of the network.

Server

Server is the host a computer which stores data and software's that can be accessed by the client computers. Data communication and real-time processing are the main tasks of the server. There are mainly three types of servers: File server, Application server and Database server.

* File serves allows sharing the same files from the common, shared disk drive. * Database servers not only allow accessing the files but allow the database

Processing on those files, this makes it more powerful then files servers.

* Print servers deals with the print request on the network.

Client computers

Client computers are also known as workstations. Client computer helps to access the network and the data on the server computer. Client computers are at the user's end are most common to us. Even the desktop can be a client computer.

Network Interface Card

Network Interface card (NIC) is the first thing to check for installing the network. We might have a computer but it may be of no use without NIC. The NIC allows the computer to be physically connected to the other computers on the network, the connection is made possible with the help of cables and other network devices.

Network Cables and Hubs

Network cables are as important as any other components, as it provides the physical connection between the two computers. It works like a motorway allows all the traffic to pass, in the same way cables allow electronic transmission which carries the data. But cables play a very important role in the selection of the network and also selecting the topology. And network hubs are the devices which help to extend the network. It also works as the connection between the two computers. We will further see the characteristics of hub in details.

Network Operating System

Network Operating system (NOS) is the software which helps to control the network. Any NOS is provided into two sets of software: one which runs on server and the other which runs on the client. NOS on the server help file server, application server and database server to operate. While NOS on the client side provides data link layer and network layer, NOS should work together with client's own operating system.

Types of LANs

Local Area Network (LAN) is divided into different types. All these types of LANs are nothing but the protocols which are used by the LAN to communicate. Each of them has unique characteristics like speed, capacity of hosting and many more. We will further see all of them in details.

Ethernet (IEEE 802.3)

Ethernet is the most common type of LAN which may be used by the almost 70 percent of the LANs. In the formalization of standard by Institution of Electrical and Electronics Engineers (IEEE) it is known as IEEE 802.3. Ethernet was originally developed by Xerox, DEC and Intel. Ethernet uses a connection-based media access technique called carrier sense multiple access with collision detection (CSMA/CD). Like the other access techniques CSMA/CD is easy to understand. The concept of CSMA/CS is to wait until the line is free and then transmit. CSMA/CD work ok by the time no two computers try to transmit at the same time. But if it happens it is known as collision and the outcome is that two messages collide and destroy each other.

Types of Ethernet

Ethernet can be classified as either baseband or broadband. Baseband uses digital channel, so it carries only one single transmission at one moment. Broadband uses analogy signalling and splits the cable into many different channels so more then one transmission can be possible at same time. The original specification of Ethernet was a 10 Mbps data rate using baseband signalling or thick coaxial cable which is also known as 10Base-5, capable of running 500 meters between hubs. But today Ethernet is further divided into two types namely Fast Ethernet and Gigabit Ethernet.

Fast Ethernet

It is basically same as Ethernet except the speed of transmission over the network. A normal Ethernet transmits at the speed of 10 Mbps and the Fast Ethernet can transmit at the speed of either 100 Mbps. Fast Ethernet uses different network connector/hubs and NIC which more expensive. The cables used are category 5 twisted pair or fiber optic. Fast Ethernet is mostly used with the Backbone Networks

Gigabit Ethernet (IEEE 802.3z)

Gigabit Ethernet is the most recent development of the Ethernet which communicates at the speed of 1 Gbps. Gigabit Ethernet is primarily used for the backbone will be used for the workstation and severs in future. It can be used with the fiber optic cabling. Gigabit Ethernet is again mostly used by Backbone networks.

Token Ring (IEEE 802.5)

Token Ring is the next popular topology; almost 20 to 25 percent of the LANs are token ring. Token Ring was originally developed by IBM and since then was standardized by IEEE as IEEE 802.5. Token Ring is less popular as compared with Ethernet. In token ring the computers are connected in such a method that the signals travels around the network from one computer to another in a logical ring. A single token passes around the ring from one computer to another and if the computer has nothing to transmit then it simply passes the token on to the next workstation on the network. Topology used by token ring is the mixture of star and ring topology which is star-wired ring using twisted pair or fiber optic cable. Transmission speed is of 4 Mbps or 16 Mbps.

ARCNET

Arcnet (Attached Resource Computing Network) is another popular peer-to-peer LAN. Arcnet was developed by Datapoint Corporation in1977 with the need for the low-cost pc LANs. It is baseband token-passing bus or star architecture. Its topology is a bus-like Ethernet, but it uses a token-passing media access control like token ring. The main reason for the popularity of Arcnet is due to its low cost. The transmission of Arcnet over coaxial cable is at 2.5 Mbps. Later on transmission over twisted pair and fiber optic cable are also added. The new Arcnet Plus transmits at 20 Mbps over coaxial cable.

FDDI

Fiber Distributed Data Interface (FDDI) is a set of standards for data transmission on the fiber optic cables in LAN. FDDI is based on the token-ring. As FDDI can cover large geographical area, it supports thousands of users to work on LAN. It also helps to connect to LANs which are over a very large distance. At present FDDI is mainly used for the backbone networks of the wide are networks. It can be extended in the range of 200 kms. The bandwidth is 100 Mbps which is far better then Ethernet. FDDI network contains two token rings; one of it is for the backup in case of the primary ring failure. And when second ring is not need for the backup, it can carry data; extending the capacity to 200 Mbps. FDDI uses dual ring physical topology. Transmission normally occurs on one of the ring but in the case of failure, the system still keeps the information moving by using portion of second ring to create a new completed ring.

Wireless LANs (IEEE 802.11)

All the LANs are not connected through cables; some of them are wireless LANs. Although wireless LANs are used in a very less percentage in comparison to other types of LANs. The growth will be seen in the near future. Wireless LANs transmit through air using high frequency radio signals or infrared light beams or laser to communicate. It used protocol similar to Ethernet that is CSMA/CD. Wireless LANs are further divide into to namely Infrared Wireless LANs and Radio Wireless LANs.

Infrared Wireless LANs

Infrared Wireless LANs are the least flexible because most require a direct line of sight between the transmitters and receivers, which is mounted in fix position. This is the only reason that most direct-line-of-sight infrared LANs are only between the hubs. The connections of the hubs to the workstations are done using the wires. Infrared LANs uses less wire and is also very useful when the communication is between builds or two different sites. The main disadvantage is, it is very expensive and has very poor security, and they only provide speed of 1-4 Mbps, which is relatively very slow as compared to cables.

Radio Wireless LANs

Radio waves travel in all directions and through non-metal objects, which makes them more flexible then infrared transmission. Most radio LANs have a NIC within the computer that is connected to external transmitter. The external transmitter transmits radio signals to a receiver that acts like a network hub and enables wireless computers to communicate with each other and with traditional wired network. Radio LANs have a range of 100-500 feet but can be up to 1000 feet in the area without any obstructions or the sources of interference. Laptop can be the best example for the use of wireless LAN, which is helping mobile computing to grow. Laptops are able to communicate with the use of Radio PCMCIA NIC for the laptops.

Selecting a LAN

Selection of the LAN is not easy. When selecting the type of LAN to set up in the organisation or the business or office we need to keep lots of things in mind. We also have to find out the required components at the best price. As market is full of competitors who claim to provide best products at cheap prices but are not doing so. There are lots of other things to be kept in mind for the selection of the right LAN.

Networks Needs

The first thing to decide is the specific need of our network. The number of client computers, further have to think that the network which we will select has any scopes for expansion or not. So let's find out many other points which we should keep in mind while selection of the LAN.

Following is the list includes all the criteria for the selection of the LAN.

Network Needs

?  Number of client computers

?  Number of dedicated servers

?  Distance between computers

?  Internetworking requirements

?  Specific application needs

?  User training, documentation, and network policies

?  Future growth

Technology

?  Protocol

?  Cabling/Wireless

?  Network Operating System

Reliability

Easy to use

Performance

?  LAN management software

?  LAN backup software and hardware

Vendor

?  Experience with network hardware and sotware

?  Experience with your network application

?  Vendor service list

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