COMPUTER NETWORK

A computer network is a collection of computers and devices connected together via communications devices and transmission media. For examples it may connect computers, printers and scanners.


IMPORTANCE / ADVANTAGES OF COMPUTER NETWORKS

• Sharing of devices such as printer and scanner.
• Sharing of program/ software.
• Sharing of files.
• Sharing of data.
• Sharing of information.
• Sharing of single high-speed internet connection.
• Can access server centered database.
• Better communication using internet services such as e-mail, mailing list and Internet Relat Chat (IRC). 

Types of computer network                   : LAN, MAN, WAN

Network architecture                            : Client/Server, Peer to Peer

Network topologies                               : Star, Bus, Ring

Network communications technology     : Intranet, Extranet, Internet 

TYPES OF COMPUTER NETWORKS

Local Area Network (LAN) ~ A local area network is a network that connects
                                              computers and devices in a limited geographical area
                                              such as a home, school computer laboratory,
                                              office building.

Metropolitan Area Network (MAN) ~ A metropolitan area network (MAN) is a high
                                                          speed network that connects local area
                                                          networks in a metropolitan area such as city
                                                          or town and handles bulk of communications
                                                          activity across the region. 

                                                       ~A MAN typically includes one or more LAN
                                                         but covers a smaller geographic area than a
                                                         WAN.

Wide Area Network (WAN) ~A wide area network is a network that covers a large 

                                             geographical area such as country or the world.

                                           ~WAN combines many types of media such as telephone
                                             lines, cables and radio waves. A WAN can be one
                                             large network or can consist of two or more LANs
                                             connected together.

                                           ~The internet is the worlds largest WAN.

NETWORK ARCHITECTURE 

Client/ Server

• A server is a computer that controls access to the hardware, software and other resources on the network and provides a centralized storage area for program. There are many type of server such as mail server, web server, file server and ftp server.
• A client is a computer that requests services from a server computer.

Peer-to-Peer

• Peer-to-Peer is a simple, inexpensive network that typically connects fewer than 10 computers. All computers it the network have equal capabilities to use the resources (hardware, software, data and files) available on the network.

NETWORK TOPOLOGIES 

Network topology is the physical arrangement of computers in a network. Common network topologies include the bus, star and ring.

* RING TOPOLOGY

- Data transmitted on the ring network travels from device to device around the entire
  ring, in one direction.

Advantages

• A physical ring topology has minimal cable requirements
• No wiring center or closet needed
• The message can be automatically acknowledged
• No collision exist between nodes.

Disadvantages

• If any node goes down, the entire ring goes down
• Troubleshooting is difficult because communication is only one way
• There will be a limit on the distance between nodes

* BUS TOPOLOGY

- The bus in a bus network transmits data, instructions and information in both
   directions.

Advantages

• Easy to implement and extend
• Cost effective as only a single cable is used
• Cable faults are easily identified 

Disadvantages

• Limited cable length and number of stations.
• If there is a problem with the cable, the entire network goes down.
• Maintenance costs may be higher in the long run.
• Performance degrades as additional computers are added or on heavy traffic.
• Proper termination is required (loop must be in closed path).

* STAR TOPOLOGY

- All data that transfers from one node to another passes through the hub, in both
  directions.

Advantages

• Easy to install and wire
• No disruptions to the network then connecting or removing devices
• Easy to detect faults and remove parts
• More suited for larger networks
• Easy to expand network
•  Easy to troubleshoot because problem usually isolates itself

Disadvantages

• Failure of the central hub causes the whole network failure.
• It is slightly more expensive than using bus topology.
• Requires more cable.

NETWORK COMMUNICATIONS TECHNOLOGY

Internet ~ An internet is a public network. It is worldwide collection of networks that
                links millions of businesses, government agencies, educational institutions
                and individuals. 

Intranet ~ An intranet is a private network within an organization that resembles the 

                internet. Organizations use intranets to provide information to their
                employees. 

Extranet ~ An extranet is a private network that connects more than one
                organizations. Many organizations use the Internet technologies to allow
                suppliers, customers and business partner limited access to their networks.