Chapter 8 - Communication and Network

Connectivity is capability of computer to share information with other computers. The concept of connectivity common used in network. Network can be set up based on the user's needs. Computer network is a communication system which connect two or more computers to allow exchange of information and data and share resources. There are four basic elements in a communication system.

• Sending and receiving devices – There are often a computer or a specialized communication device. Accept messages in the form of data, information and instructions.
• Communication channel – It is a transmission and connection medium either physical or wireless that carries the data from one computer to another. Physical connections such as telephone lines, ethernet cables, coaxial cable and fiber-optic cable. Type of wireless connections are radio frequency (RF) which is Wi-Fi (wireless fidelity), Bluetooth (short-range) and WiMax (extends Wi-Fi), Microwave, Satellite, Global positioning system (GPS) and Infrared (short distance).
• Connection devices – They acts as an interface between sending and receiving devices. They convert outgoing messages into packets that can travel across the communication channel. Telephone modem, DSL (digital subscriber line), Cable modem and Wireless modem(WWAN) are type of connection devices.
• Data transmission specifications – It is a rules and procedures that coordinate the sending and receiving devices and define how the messages will be sent across the communication channel.

There are some specialized terms to describe computer network.

• Node – any device connected to a network
• Client – a node that requests and uses resources available from other nodes
• Server – a node that shares resources with other nodes, dedicated servers specialize in performing specific tasks, for example application server, communication server, database server, file server, printer server and Web server
• Directory server – a specialized server that manages resources such as user accounts for an entire network
• Host – any computer system connected to a network that provides access to its resources such as large centralized computer
• Router—a node that forwards or routes data packets from one network to their destination in another network
• Switch – the center or central node for other nodes, previously done by something called a hub
• Network interface cards (NIC) – connects the computer to a network
• Network operating system (NOS) – software to control and coordinate activities between computers on a network
• Network administrator – a computer specialist

There are six network types :

LANs

• Computers and devices linked in close proximity to each other
• Linked by cable
• With gateways, LANs can be connected to other LANs or any other type of network. Ethernet is one standard for connecting network nodes together.

Home Network

• LANs are now being commonly used by individuals in home/apartments which allow different computers to share resources including a common Internet connection
• can be connected by various means including a wireless LAN (WLAN) that uses radio frequencies to connect computers
• all communications pass through the network’s centrally located wireless receiver or base station

Wireless LAN

• wireless local area network
• All communications pass through the network’s centrally located wireless access point
• Wireless access points that provide Internet access are widely available in public places such as coffee shops, libraries, bookstores, colleges, and universities. These access points are known as hotspots and typically use Wi-Fi technology

Personal Area Network

• works within a very small area
• Connects cell phones to headsets, PDAs to other PDAs, for example keyboards to cell phones

MANs (metropolitan area network)

• also known as a regional network
• Network linking nodes and resources within the geographical bounds of a city
• Cellular phones can extend the reach of a MAN
•  it is owned either by a group of organizations or by a single network service provider that provides network services for a fee

WANs (wide area networks)

• Countrywide and worldwide networks
• Use microwave relays and satellites to reach users
• Internet is the widest WAN

Wireless devices are getting develop rapid and most spread used nowadays, for example tablets, smartphones and wearables. They apply the wireless revolution which is a revolution that will dramatically affect the way we communicate and use computer technology.

Bandwidth is a measurement of the width or capacity of the communication channel. Effectively, it means how much information can move across the communication channel in a given amount of time. For example, the text documents transmit through a short bandwidth but video and audio need a wider bandwidth to transmit. There are four types of bandwidth :

• Voiceband –  It is a low bandwidth and for standard phone line. Text documents can use this bandwidth but too slow for many types of transmissions especially high-quality video
• Medium band – This bandwidth is capable of very-high-speed data transfer with special leased lines to connect minicomputers and mainframes as well as to transmit data over long distances (for larger computer systems).
• Broadband – It is used for high-capacity transmissions (DSL, cable, satellite connections) and specialized high-speed devices. It can effectively transmits high-quality video and other communication needs.
• Baseband – It is widely used to connect individual computers that are located close to one another. It can only carry a single signal at a time.

Protocol is a communication rules for exchanging data and information between computers. There are two essential features for protocol : 

• Identification - Identifying sending and receiving devices. Every computer on the Internet has a unique numeric address called an IP Address, Internet Protocol address. Domain Name Server (DNS) is a system which convert text-based addresses to numeric IP addresses.

• Packetization – Allows message to be broken into small parts/packets. Each packet is then sent separately over the Internet, possibly traveling different routes to one common destination. At the receiving end, the packets are reassembled into the correct order at destination. It is easier to transmit over Internet through various interconnected networks.

Through this chapter, I can more understand about the six types of computer network. I also know how a communication system and computer network work. The communication system and computer network are able to connect the people all over the world.