End-user computers or terminals
The access points for users of a network are known variously as clients, nodes, workstations or, most commonly, just PCs. It is best to use the term ‘client PC’, as this helps distinguish clients from servers which may also be PC-based. To work on the network each client must have networking software such as Novell Netware or TCP/IP installed (see later section). Of course, a physical connection to the network is also required. For a PC on an office LAN, this is provided by a network interface card in one of the PC’s slots. The card is then attached to the network cabling. For a PC at home which is linked to the Internet, the network card is replaced by a modem.
Data communications equipment orn telecommunications processors
As well as the physical cables that link the computers, there are also other important components of the complete telecommunications system that have to be purchased by a business. These are the pieces of hardware that are used to link the servers and clients and different networks together. These devices can be thought of as connectors located between client computers and servers. Collectively, these processors can be called telecommunications connectors or gateways, but they are usually referred to by their specific names, such as hubs, multiplexers, bridges and routers. In a company that needs to use gateway devices, a specialist is required to maintain them. Modems and network interface cards also fit into this category.
Communications devices
The following are options for connecting telecommunications equipment.
Data communications equipment orn telecommunications processors
As well as the physical cables that link the computers, there are also other important components of the complete telecommunications system that have to be purchased by a business. These are the pieces of hardware that are used to link the servers and clients and different networks together. These devices can be thought of as connectors located between client computers and servers. Collectively, these processors can be called telecommunications connectors or gateways, but they are usually referred to by their specific names, such as hubs, multiplexers, bridges and routers. In a company that needs to use gateway devices, a specialist is required to maintain them. Modems and network interface cards also fit into this category.
Communications devices
The following are options for connecting telecommunications equipment.
- Dial-up networking (DUN) facilities allow users to access a network at a remote location via a modem. The modem (modulator–demodulator) works by converting data between digital and analogue form. The modem receives analogue data (for example as transmitted via an analogue telephone line) and converts these into digital data so that the computer can make use of them. Similarly, the modem converts outgoing digital data into an analogue signal before transmitting them.
- Digital telephone exchanges support an integrated services digital network (ISDN) standard that allows data transfer rates of 64 kbps. An ISDN telephone line provides two separate ‘channels’, allowing simultaneous voice and data transmissions or combined to give a transmission rate of 128 kbps. Since ISDN lines transmit digital data, a modem is not required to make use of the service. Instead, a special terminal adaptor (often called an ‘ISDN modem’) is used to pass data between the computer and the ISDN line
- Asymmetric digital subscriber line (ADSL) services makes use of existing telephone lines to provide very high data-transfer rates. ADSL or DSL is usually simply referred to as ‘broadband’ Internet access when offered by ISPs for home and small-business users across their phone lines. Although the bandwidth offered by such services is usually shared by a number of users, ADSL offers many of the benefits associated with ISDN and the potential of data transfer rates of up to 24 Mbps. ADSL is known as ‘asymmetric’ since it offers different speeds for download and upload of data. A range of different options are available for ADSL Internet packages from 512 kbps download. Up to 24 Mbps download is possible across some telephone lines. Variations on ADSL include Annex M which can more than double upload speeds and Annex L which can increase the range of coverage.
- Satellite communications systems can be used to receive data at very high speeds in remote locations. Such systems are used to beam back news stories from remote locations. The satellite dishes can be fixed or mobile, for example fixed to a car roof.
- Cable modems make use of the fibre-optic cables that have been installed by cable television companies such as Virgin Media. Services tend to be restricted to heavily populated areas, such as cities and large towns. Cable modems offer very high datatransfer rates, up to a maximum of 100 Mbps.
As more individuals and organisations gain access to high-speed services (known as broadband services, as opposed to traditional ‘narrowband’ services), data transfer speeds are more commonly measured in terms of thousands (kbps) or millions (Mbps) of bits per second. The standard ADSL broadband speed when it was first introduced was 512,000 bps, 512 kbps or 0.512 Mbps and it requires a specific ADSL modem. However, as we will see below, providers have introduced a range of speeds by limiting this speed to enable them to offer a range of packages.
Options for consumer broadband services
Competition in the marketplace amongst broadband providers has caused a great increase in the Internet access options available for consumers and small businesses. While broadband was originally introduced as an ‘always-on’ connection, some Internet service providers (both ADSL and cable companies) have offered lower-speed options while others have capped usage at a fixed number of hours per month or put limits on the amount of data transferred. For example, in 2011, one cable company offered four levels of speed (10Mb, 20Mb, 50Mb and 100Mb) with unlimited downloads and another provider offered 20Mb with a 2Gb monthly usage allowance or 20Mb with unlimited monthly usage. Given the complexity of choice, several Internet services have been created to compare the offerings (Google ‘compare broadband’). For example, visit Broadband Checker (www. broadbandchecker.co.uk) to find out the latest choices in your area or see thinkbroadband (www.thinkbroadband.com) for a wide range of suppliers. The choices in selecting business broadband for small business users are similar to those for home users.
Options for consumer broadband services
Competition in the marketplace amongst broadband providers has caused a great increase in the Internet access options available for consumers and small businesses. While broadband was originally introduced as an ‘always-on’ connection, some Internet service providers (both ADSL and cable companies) have offered lower-speed options while others have capped usage at a fixed number of hours per month or put limits on the amount of data transferred. For example, in 2011, one cable company offered four levels of speed (10Mb, 20Mb, 50Mb and 100Mb) with unlimited downloads and another provider offered 20Mb with a 2Gb monthly usage allowance or 20Mb with unlimited monthly usage. Given the complexity of choice, several Internet services have been created to compare the offerings (Google ‘compare broadband’). For example, visit Broadband Checker (www. broadbandchecker.co.uk) to find out the latest choices in your area or see thinkbroadband (www.thinkbroadband.com) for a wide range of suppliers. The choices in selecting business broadband for small business users are similar to those for home users.
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