INFO 2 CH 17 - ICT Networks

All organizations and individuals need to communicate, to send information to and receive information from other organizations/individuals. ICT has transformed the way we communicate. New methods have been developed, each with its own features and advantages for example: 

• Email
• Fax
• Internet
• Internet conferencing
• Instant messaging
• Mobile phones
• Short message service (SMS) 
• video conferencing
• View data
• Voiceover internet protocol
• Personal digital organizer
• Intranet
• Extranet

Public networks such as the internet, to which anyone cam connect to mean that millions of computers can be linked together. This means that users can:

• Communicate with each other quickly
• Share files
• Use browser software to access web pages
• Search for information

Many school and colleges have installed Virtual Learning Environments (VLE) software. A VLE allows students and their teachers to interact online. A VLE offers the following features.

• Access to course material and learning resources. Materials should be varied and include course content as well as quizzes and a range of exercises. Teachers can develop these materials using straight forward templates. A student can work through at their own pace, receiving feedback to reinforce understanding
• Methods of tracking a student’s progress in working through online material and assessment marks. Each student is able to check their individual progress
• Means of communication between the student and the teacher that can provide feedback on their progress.
• Means of communication with other students on the course using discussion forums and chat rooms.

A computer network consists of two or more computers and peripherals that are linked together. These links can be made with cables. A wireless network uses radio waves, in the same way as TV to make the links. A wireless network following a common protocol is called Wi-Fi.

Wireless networks are used in many homes. Such a wireless network is easy and inexpensive to set up. Home Wi-Fi can be set up so that several members of the household can access the internet at the same time. 

Wireless networks are also made available in places such as hotels. They are known as Wi-Fi hotspots. The greater the number of Wi-Fi hotspots that are available the easier it is for someone with a laptop to keep up to date and in touch while on the move.

With a large network, issues such as access to the network, security, data sharing and maintenance need considerable management; a network manager with a team of technicians is employed to carry out this work. Such a network can be called a managed network. There are two main types of network organizations:

• Server-based
• Peer-to-peer

Server-based networks have a central computer called a server. Other computers in the network are called clients. Devices are treated as either servers or clients; they cannot be both. Server-based networks are usually used by large organizations. 

Servers provide central services such as backup and software installation as well as providing centralized storage of data accessible to all workstations on the network. Clients send requests for services, such as the retrieval of data to the appropriate server which carried out the required processing. Some processing tasks are carried out by the server and others on the client computers. 

Large networks may have more than one server. The performance of this sort of network is heavily dependent on the servers. They need to have fast processing speeds, and relatively expensive and server-based networks can be complicated to install. If a server fails then the clients on the network cannot access the resources provided by the server. 

A peer-to-peer local area network is a very simple network that provides shared resources to the computers that make it up. All the computers in the network have the same status and there is no central server. 

Computers on a peer-to-peer network can access files and devices on another linked computer providing the appropriate access privileges have been set. Any compute can communicate and exchange data with any other on the network. 

Installation of software takes more time, as it has to be installed on each station. Backing up must also be done separately for each individual station. As a server is expensive to buy, a small peer-to-peer network would be much cheaper than a small server-based network. 

Both types of network can share printers and other peripherals. Both types of network can be used to send and receive emails from other networks users. 

Communication Devices

To connect a computer to a local area network, a network interface card is needed. The card is an electronic printed circuit that fits inside the computer into an empty slot on the computer’s motherboard. It allows the computer to be recognized by the network and allocates it a unique identifying number; the network interface card determines the maximum speed of data transmissions that will be available around the network.

 Commerunication Devices - Individual users

A number of devices are needed to enable an individual home user to link to the internet. A modem is a device that can be plugged into a computer or is housed inside a computer. It is connected to a telephone line and provides access to a wide area network. The modem converts the digital signals that is used within the computer into the analogue form that is required for transmission over a telephone wire and convert the analogue signal to a digital one for incoming messages.

A broadband modem also connects a computer to the telephone line. It uses Asymmetric Digital Subscriber Line (ADSL) modulation technology and special compression techniques to achieve much faster transmission rates. A broadband modem links a single computer to the internet and the user is able to stay online all day. 

Wireless broadband modem routers can be used by subscribers to broadband. The router allows serval devices to share the internet connection wirelessly. The wireless adapter translates the digital data from the device into a radio signal. The signal is transmitted using an antenna. When a device sends data to the internet, the router receives a radio signal form the device and changes the data from radio-wave form to digital form. The router is connected to a telephone socket with a cable and the digital data is sent via this to the ADSL line. Every phone extension that is in use needs a mircofilter to cut out the broadband interference. 

Communication Devices - Large organizations

Extra hardware is required when linking computers together to form a network. A large organisation will maintain a number of servers. These are used to manage the traffic around the computers in the network. Attached are hard disks with very high storage capacity that stores databses, user files and software that is shared between users and download to users' client computers.

A switch handles the efficient transfer of data between different sections of the network. A repeater may be needed to amplify the signal on long stretched of cable.

Data transfer media 

Cables are the most common form of transmission media used to connect network stations to the rest of the network. The network cabling connects to the network interface card. Cables are usually made of copper wire. Common examples are Ethernet cabling (coaxial, like a television aerial) and UTP (unshielded Twisted pair) cabling. Fiber-optic cables are become more common; they are faster than copper cabling but more expensive. 

Networking Software

Special network operating system features are required to enable the running and management of a network. It sets up the correct protocols to be used across the network. A protocol is a standard set of rules that defines how communications take place between computers.

A modem driver, a program that controls the broadband modem. A browser program is needed to view web pages written in HTML.

The user needs to subscribe to an Internet Service Provider (ISP). The ISP normally provides an email address to enable the user to send and receive emails and a limited amount of web space so that the user can set up a website. The ISP has a host computer that deals with communications and stores data such as email messages. 

Standards and Procedures 

A standard is a common way of doing something. Without standards, networking would be limited to communicating between computers of the same type. The use of standards allows each device to interpret correctly the data that it receives. Many procedures need to be carried out if users are to access any network safely and easily. These procedures only have to be undertaken because of the use of the network- they do not in themselves carry out any user tasks. 

It is vital that every user of a public network installs a virus scanner. A virus scanner is software that is used to check any virus. Spyware is software that secretly gathers information about a user through there internet connection. In a large, business network, a number of regular procedures need to be carried out. These include:

• Maintaining software to the network: new software must be installed on the appropriate server and maintenance modifications made from time to time.
• Adding, deleting and modifying user accounts; this involves aspects such as access rights, memory allocation and monitoring use
• Carrying out regular backups
• Monitoring of network traffic and usage
• Maintaining security across the network

The internet is a very large number computer networks that are linked together across the world via telecommunications systems. Messages and data are sent from the source computer. Through a number of other computers until the destination computer is reached. 

The World Wide Web (Web) is a vast collection of pages of information in multimedia form held on the internet. Pages can contain images, videos, animation and sounds. 

Web pages are written in a language called HTML (Hypertext Mark-Up Language). Web pages can be created and website built using web design software.

Accessing the internet from home

Once connected to the internet, the user can:

• Access pages of information on the web
• Save webpages
• Leave messages on bulletin board
• Share user videos
• Talk to friends on a social networking website
• Send and receive email

The ISP may also provide:

• Free web space to set up and edit your own web pages
• Additional emails addresses
• Latest news
• It’s won search engine for searching the web
• Its own internet shopping facility

Other ways of accessing the internet 

Big organizations where a large number of users need to access the internet are likely to find that a modem and dial-up connection, and even ADSL broadband facilities, will not meet their needs. The user’s computers are likely to be organized into a local area network which is linked to the internet via a terminal server. The organization is likely to have a permanent link to the internet via a fiber-optic cable. 

The internet and Business

With hundreds of millions of people across the globe using the internet, commercial interest have recognized the opportunities offered by this new technology. The internet offers business many opportunities. For example, they can:

• Market their products to a worldwide audience with a website
• Carry out research
• Sell products directly over the internet
• Use video conferencing 
• Use Electronic Data Interchange (EDI) to communicate with suppliers.
• Use intranets and extranets to get up-to-the-minute information
• Use email to communicate quickly

Commercial websites 

Many business use websites to promote themselves. Some have found that not only is it much cheaper than conventional advertising but it reaches a much larger audience. 

The internet offers a number of facilities that the company can use to encourage use of sites by directing customers to it. The company can:

• Register with a search engine
• Place an advert 
• Add a meta tag to the webpage – to provide information that can be used by search engines
• Add a function to their own sites so that visitors can add the email address of friends. 

Intranet 

An intranet is a network based on internet protocols that belongs to an organization. It is made up of webpages which can be accessed by standard internet browser software. The intranet is only accessible to employees of the organization and must be accessed using an identity code backed up with a password. It can be used across a local area network. A wide area network or normal internet lines, when it is protected from unauthorized access by a firewall. 

Extranet 

An extranet is an intranet that is made partially accessible to people outside the organization. These people must be authorized. An extranet can only be accessed by someone who has a valid username and password. The user identity will determine exactly which parts of the intranet can be viewed by the user.

Two companies could use an extranet to exchange large volumes of data using Electronic Data Interchange (EDI).