What is a Network?A 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 network may be linked through cables, telephone lines, radio waves, satellites, or infrared light beams.

INTRODUCTION TO NETWORKS

Why You Need a Computer Network?

Sharing data through the use of floppy disks is not an efficient or cost-effective manner in which to operate businesses.

Businesses needed a solution that would successfully address the following three problems:

• How to avoid duplication of equipment and resources

• How to communicate efficiently

• How to set up and manage a network

Businesses realized that networking technology could increase productivity while saving money.

A local area network (LAN) connects your company's computers, allowing them to share and exchange a variety of information. Here are some of the ways a computer network can help your business:

File sharing

Have you ever needed to access a file stored on another computer? A network makes it easy for everyone to access the same file and prevents people from accidentally creating different versions.

Printer sharing

If you use a computer, chances are you also use a printer. With a network, several computers can share the same printer. Although you might need a more expensive printer to handle the added workload, it's still cheaper to use a network printer than to connect a separate printer to every computer in your office.

Communication and collaboration

It's hard for people to work together if no one knows what anyone else is doing. A network allows employees to share files, view other people's work, and exchange ideas more efficiently. In a larger office, you can use e-mail and instant messaging tools to communicate quickly and to store messages for future reference.

Organization

A variety of network scheduling software is available that makes it possible to arrange meetings without constantly checking everyone's schedules. This software usually includes other helpful features, such as shared address books and to-do lists.

Shared Internet access

If you have several computers but just one phone line, a network makes using the Internet much easier.

ADVANTAGES OF  NETWORK

Speed

Sharing and transferring files within Networks are very rapid. Thus saving time, while maintaining the integrity of the file.

Cost

Individually licensed copies of many popular software programs can be costly. Networkable versions are available at considerable savings. Shared programs, on a network allows for easier upgrading of the program on one single file server, instead of upgrading individual workstations. 

Security

Sensitive files and programs on a network are passwords protected (established for specific directories to restrict access to authorized users) or designated as "copy inhibit," so that you do not have to worry about illegal copying of programs.

ADVANTAGES OF  NETWORK

Centralized Software Management

Software can be loaded on one computer (the file server) eliminating that need to spend time and energy installing updates and tracking files on independent computers throughout the building. 

Resource Sharing

Resources such as, printers, fax machines and modems can be shared. 

Electronic Mail

E-mail aids in personal and professional communication. Electronic mail on a LAN can enable staff to communicate within the building having tot to leave their desk. 

ADVANTAGES OF  NETWORK

Flexible Access

Access their files from computers throughout the firm. 

Workgroup Computing

Workgroup software (such as Microsoft BackOffice) allows many users to work on a document or project concurrently

DISADVANTAGES OF  NETWORK  

Server faults stop applications being available

Network faults can cause loss of data.

Network fault could lead to loss of resources

User work dependent upon network

System open to hackers

Decisions tend to become centralized

Could become inefficient

Could degrade in performance

Resources could be located too far from users

TYPES OF NETWORKS

NETWORK CAN BE MAINLY CLASSIFIED INTO TWO CATEGORIES.

1. Wired Network – System are connected through cable media is called as wired Network.

2. Wireless Network – Systems are connected through satellite is called as wireless Network

NETWORK

WIRED NETWORK

WIRELESS NETWORK

TYPES OF NETWORKS

BASED ON THE DISTANCE NETWORK CAN BE CLASSIFIED INTO THREE CATEGORIES.

1. LAN – LOCAL AREA NETWORK2. MAN – METRO POLITON AREA NETWORK3. WAN – WIDE AREA NETWORK

NETWORK

LAN(Local Area Network)

MAN(Metro Politon Area

Network)

WAN(Wide Area Network)

LOCAL AREA NETWORK (LAN)

A network is said to be Local Area Network (LAN) if it is confined relatively to a small area. It is generally limited to a building or a geographical area, expanding not more than a mile apart to other computers.  

Advantages of Local Area Network (LAN):

Workstations can share peripheral devices like printers. This is cheaper than buying a printer for every workstation.

Workstations do not necessarily need their own hard disk or CD-ROM drives which make them cheaper to buy than stand -alone PCs.

Advantages of Local Area Network (LAN):

User can save their work centrally on the network’s file server. This means that they can retrieve their work from any workstation on the network

They don’t need to go back to the same workstation all the time. Users can communicate with each other and transfer data between workstations very easily.

One copy of each application package such as a ms-office, visual basic etc. can be loaded onto the server and shared by all users instead of onto every workstation.

Disadvantages of Local Area Network (LAN):

Special security measures are needed to stop users from

using programs and data.

Networks are difficult to set up and need to be maintained by

skilled technicians.

If the file server develops a serious fault, all the users are

affected, rather than just one user in the case of a stand-alone

machine.

METROPOLITAN AREA NETWORK (MAN)

Metropolitan Area Network (MAN) covers larger geographic areas,

such as cities. Often used by local libraries and government agencies

often to connect to citizens and private industries.

WIDE AREA NETWORK (WAN)

Wide Area Networks (WANs) connect larger geographic areas,

such as London, the UK, or the world. In this type of network dedicated

transoceanic cabling or satellite uplinks may be used.

BASED ON THE OPERATING SYSTEM NETWORK CAN BE CLASSIFIED INTO TWO CATEGORIES.

1. PEER – TO – PEER 2. CLIENT – SERVER TECHNOLGY

NETWORK

PEER O PEERCLIENT – SERVER

TECHNOLOGY

Peer-to-Peer

Peer-to-peer network allow users to share resources and files located on their computers and to access shared resources found on other computers.

Peer-to-peer network do not have a file server or a centralized management source.

Peer-to-Peer

In a peer-to-peer network, all computers are considered equal; they all have the same abilities to use the resources available on the network.

Peer-to-peer networks are designed primarily for small to medium local area networks.

Advantages of a peer-to-peer network:

Less initial expense No need for a dedicated server.

Disadvantages of a peer-to-peer network:

Decentralized - No central repository for files and applications. Security - Does not provide the security available on a

client/server network.

Client/server network operating systems allow the network to centralize functions and applications in one or more dedicated file servers.

The file servers become the heart of the system, providing access to resources and providing security.

Individual workstations (clients) have access to the resources available on the file servers.

The network operating system provides the mechanism to integrate all the components of the network and allow multiple users to simultaneously share the same resources irrespective of physical location. Novell Netware and Windows 2000/2003 Server are examples of client/server network operating systems.

CLIENT-SERVER TECHNOLOGY

Client/Server Network

Advantages of a client/server Network:

Centralized - Resources and data security are controlled through the server.

Scalability - Any or all elements can be replaced individually as needs increase.

Flexibility - New technology can be easily integrated into system.

Interoperability - All components (client/network/server)work together.

Accessibility - Server can be accessed remotely and across multiple platforms.

Disadvantages of a client/server Network:

Expense - Requires initial investment in dedicated server.

Maintenance - Large networks will require a staff to ensure Efficient operation.

Dependence - When server goes down, operations will cease across the network.