INTERNET SERVICES

COMPUTER NETWORK

What is network?

• A network is a collection of computers, servers, mainframes, network devices, peripherals, or other devices connected to one another to allow the sharing of data. An excellent example of a network is the Internet, which connects millions of people all over the world. Below is an example image of a home network with multiple computers and other network devices all connected to each other and the Internet.

Cmmunication Device & Transmission Media

Communication Devices :

• A communication device is any type of hardware capable of transmitting data,instructions and information between a sending device and a receiving device.

Type of communication devices :

• Dial-up Modem - can convert digital signals to analog signals,so that data can travel along an analog telephone line.
• Digital Modem (ISDN,DSL,Cable Modem) - sends and receives data and information to and from a digital line.
• Wireless Modem - some mobile users have a wireless modem that uses the cell phone network to connect to the internet wirelessly from a notebook computer,a smart phone or other mobile devices.
• Network Card - enables the computer or devices that does not have built in networking capability to access a network.
• Wireless Access Point - A central communication device that allows computer and devices to transfer data wirelessly.
• Router - connects multiple computers or other routers together and transmits data to its correct destination on a network.
• Switch - similar to a hub but more sophisticated including functionality tha alow it to control and manage data transmissions.
• Hub - allows multiple conection to  the network.

Router

Hub 

Dial up modem

Switch

Transmission Media : 

• Materials or substances capables of carrying one or more signals in a communications channel.

Physical Transmission :

Type	Description
Twisted Pair Cable	Consists of one or more twisted-pair wires bundled together.            Widely used transmission media for network cabling and telephone system.
Coaxial Cable	Consist of a single copper wire surrounded by at least three layers:        An insulating material        A woven or braided metal        A plastic outer coating.
Fiber Optic	A transmission media that uses glass or plastic fiber to carry light (laser) signals.

Wireless Transmission Media :

Type	Description
Microwave	Provide a high speed signal transmssion: *Microwave transmission,often called fixed wireless,involves sending signals from one mocrowave station to others.
Communication Satelite	A space station that receives microwave signals from an earth based station,amplifies the signals,and broadcast the signal back over a wide artea to any number of eath based stations.
Infrared	A wireless transmission medium that sends  the signals using infrared light waves.
Broadcast Radio (Bluetooth,ultra Wideband (UWB),Wi-Fi,WiMAX)	Disributea a radio signals through the air over long distances such as between cities,regions and coutries and short distances such as within an office or home.
Cellular Radio (2G,3G,4G)	A form of broadcast radio that is used widely for mobile communications,specifically wireless modems and cell phones.

Advantages of Network :

Easy communiccation and speed

• People can communicate efficiently by using network such as emails,instant messaging,telephone,video conferencing,chat room.etc.

Ability to share files,data and information

• It can benefit large organizations to maintain their data in an organized manner and facilities access for desired people.

Sharing hardware

• Can reduce the cost of purchasing hardware.

Sharing software

• Can reduce the cost of buying software by networking their computers because networkable versions of software are available.

Security 

• Sensitive files and programs on a network can be password protected and can only be accessed by the authorized users.

Speed

• Sharing and transferring file within networks is very rapid,depending on the type of network.This will save time while maintaining the integrity of files.

 Disadvantages of Network :

Breakdown and possible loss of resources

• Breakdown of the whole network due to ana issue of the server may lead to loss of important data of the server.

Expensive to build

• Building a network for large scale organizations are very pricey ecpecially to buy and replace cables and other hardware.

Security threats

• There are hackers who are trying to steal valueable data of large companies for their own benefit.

Bandwidth Issues

• Heavy users who consume a lot more bandwidth will affect other users.