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LAN 1

Figure 3.S A virtual network within a WAN

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LAN 2

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_Q_U_E_ST_I_O_N_S __________________________________ ___

1 Identify three characteristics of a LAN. 2 Identify two characteristics of a WAN. 3 Describe the purpose of a virtual LAN . 4 Identify four services offered by an ISP.

Discuss the characteristics and purpose of intranets, the internet and extranets

Internet

Characteristics

The internet is not the same as the World Wide Web and it is important not to get the two terms mixed up. The internet is the infrastructure provided to connect computers together across the globe using telecommunications systems such as telephone lines, leased lines, mobile phones and satellites. It uses the TCP/ IP protocol for communication between devices. Any computer with an external communication link can connect to the internet, meaning that the internet can be referred to as an OPEN network.

Purpose

Once connected to the internet, users can gain access to a number of services, for exampl~:

• Email • World Wide Web • internet relay chat (IRC - instant messaging) • File transfer

Software is required to access these services. While most services can be accessed using a web browser, there are dedicated software packages available for email (e.g. Quaicomm Eudora), file transfer (e.g. Ipswitch WSJTP) and IRe (e.g . Microsoft Messenger). Remember in an examination that you should refer to the types of software and not the brand names. These services are available for communicating all over the world. For example, you might want to send an email to somebody in Japan, chat to a friend in the next street using IRC, visit the BBC website or transfer files to update your anti-virus software.

Intranet

Characteristics

The intranet provides the same services as the internet, but only within one organisation. It is secure as it can only be used by authorised people within that organisation and will almost certainly require the use of a username and password to gain access. The intranet may be provided through a lAN or in a larger organisation it will be available through a virtual network within a WAN. Only computers that are part of the lAN or virtual network will be able to gain access to the intranet, meaning that it can be referred to as a closed network. The intranet uses the same TCP/IP protocol as the internet.

Purpose

Users of an intranet have access to the same services as they do on the internet, but they can only communicate within their own organisation. Services include:

• internal email • internal web pages • internal chat • file transfer.

As with the internet, software is required to access these services. These services are available for communication only within the organisation . For example, an employee might want to send an

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email to a colleague at the head office, chat to a colleague in the Birmingham office, find out about the Health & Safety policy from 71 the internal web pages or download a piece of software that is licensed for use within the organisation.

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Figure 3.6 A extranet

Using an intra net means that users can provide information and communicate with others knowing that nobody outside of the organisation can gain access to that information. This means that sensitive documents, such as business plans, remain confidential.

With a partner, list the facilities available on your school intra net.

Extranet

Intranet

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Characteristics

Employee on a trainB logs on to intra net from a laptop connected to the internet using a mobile phone. He is now connected to the extra net.

Users of an extra net have access to an intranet using a username and password from an internet-connected computer. Once connected to the extra net, the user has access to all the intranet services of the organisation . Access is usually provided by logging on to a secure server from a web page, although some organisations will provide secure software that has to be installed before access can be provided to the extra net.

Purpose

These services are still only available for communication within the organisation, but employees and registered users can access the

Characteristics

Intranet

services from any internet-connected computer. For example, an employee working from home may want to send an email or chat to a colleague who is away working on business in a foreign country, find out the direct telephone number for a colleague or download files needed to prepare a report.

Using an intra net means that users can provide information and communicate with others knowing that nobody outside of the organisation can gain access to that information. Confidentiality is maintained, but there is added risk that somebody could hack into the extranet because it is available from any internet-connected computer.

< Activity> List the facilities of your school network that you can access from home.

1 Describe three facilities available on the internet, intra net and extra net.

2 Explain how an intranet differs from the internet. 3 Describe the purpose of an extra net.

Discussing the characteristics and purpose In an examination, it is likely that you will be asked to discuss the characteristics and purpose of intranets, the internet and extranets. You will therefore need to be able to write a balanced argument that compares the advantages and disadvantages of each. The table below gives a summary of the characteristics and purposes.

Internet Extranet

• Enables communication within an organisation.

• Infrastructure provided to • Enables communication connect computers within an organisation

• Uses LANs or virtual networks across a WAN.

• Requires a username and password to gain access.

• Uses the TCPj lP protocol. • Only available within the

physical network infrastructure of an organisation.

together across the globe. from any internet-• Uses telecommunications connected computer.

systems such as telephone • Uses the internet to lines, leased lines, mobile provide access to an phones and satellites. intranet.

• Web pages are available to • Requires a username and anybody - other resources password to gain access. may require usernames and . Uses the TCPj lP protocol. passwords. • Available from the

• Uses the TCPjlP protocol. internet, but only to • Available to the whole employees within an

world. organisation.

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Purpose

Intranet

• Provides email communication only to other members of the organisation.

• Web pages within the organisation can be visited to find internal information about the organisation.

• Chat conversations can take place with other employees within the organisation .

• Files that belong to the organisation can be downloaded for use within the organisation.

• Information that is shared is securely retained within the organisation so that external users cannot gain access to it.

Internet

• Provides email comrnunication to any other internet-connected user.

• Web pages can be visited anywhere on the World Wide Web to fi nd out publicly available information.

• Chat conversations can take place with any other internet-connected user.

• Files can be transferred to/from any file transfer site.

Extranet

• Employees working away from the office can send and receive internal emails.

• Employees working away from the office can find internal information about the organisation.

• Employees working away from the office can chat with their colleagues.

• Employees working away from the office can download files needed to carry out their duties.

• Employees do not have to be physically within the organisation's premises but providing access from the internet means there is a security risk if a hacker can find out a username and password.

Describe client-server and peer-to-peer networks giving advantages and disadvantages of each

A client-server network is often found in medium- to large-sized organisations whereas a peer-to-peer network is often found in small organisations (e.g. local churches, a family run shop, a solicitor's practice) and homes.

Client-server network A client-server network requires at least one computer that performs the role of a server. A server performs roles such as:

• file storage • back-up • application sharing • printer management.

The client computers are all connected to the server via a switch or other network communication device. In order to access resources such as files or printers on the network, users are required to log on at the client computers using a username and password. Some client computers use swipe cards instead of usernames or finger print recognition instead of usernames and