Networking

Since their inception, one of the major roles of the computer has been the distribution of information. Originally either as a printed document, or directly by magnetic media, as disks, or tapes, the latter being referred to as either `sneaker net', or `frisbee net', depending on whether the media was carried or thrown across the room.

Serial connections

Were the earliest form of networking, allowing two PC's to exchange data. They consisted of a telephone like connection between the serial or COM (communication) ports of two PC's. The impetus was there to create firstly LANs (Local Area Networks), then WANS (WIDE ANS), as you may guess this was driven by the US military and their need to communicate, both amongst themselves, and with any research sites they were involved with. This led to the development in the early 1980's of e-mail. The Internet was born!!!. Several manufacturers produced either (or both) PC's and Mainframe Computers all having adopted the serial line interface, as a standard.

Kermit

Not the Frog, in fact it means `The first born'. was the first program to be written as a `cross platform' application. It allowed (and still does) for example a BBC Microcomputer to connect to a mainframe running UNIX, or VMS. or to a PC or Amiga, or any combination of computers , which were capable of running Kermit.

MODEM

MOdulator DEModulator) This innovation allowed a remote PC to communicate with a mainframe. From anywhere there was a telephone line. The original Modems were known as `Acoustic couplers' and consisted of a soundproof box in which the telephone hand set was placed, in proximity to a speaker and microphone. The `coupler' was connected to the PC's serial port. Modern Modems are supplied either as a card inserted into the PC, taking over the function of one of the PC's COM ports, or as an external box, connected to a port. The major disadvantage of serial connections, is their speed, or rather lack of it. Initially modems had a speed (baud rate) of 1200 or 1200 bits per second. Technology has given us currently a speed of 56000 baud, still not good compared to an average Ethernet cards 10 MIPS (million instructions per second).

An internal modem

(Now with the advent of broadband into the home speeds of 2Meg are commonly available.

Ethernet connections

Are dependent on an Ethernet card in each PC, and are usually confined to LAN's, however it is now possible for large multi-site organisations to link smaller LAN's together, into WAN's. This requires an Ethernet switch box called a `bridge', and a dedicated line, usually installed by a telephone company. This line is often an optical (Glass fibre) line. And may include a link outside the company to the Internet, and hence the provision of e-mail becomes practical.

The Ethernet card

Nowdays onboard network connectors are the norm, however this wasn't always the case and you can still get NIC's both wired and wireless.

The ethernet cards, or NIC's (Network Interface Card) are made by a number of companies some of, which manufacture other equipment involved in the construction of networks, 3Com being an example of this type of organisation.

There are four types of interface available on Ethernet cards, however the trend is strongly towards only two of them UTP (cat5/10) and wireless.

Cards are often supplied with a number of interfaces fitted and are termed `Combo' (combination) cards.

AUI Is the oldest of these interfaces and is typified by a 15 DIN socket in the card. It required an external interface box to connect to the network wiring. This type is rarely used now. BNC has a bayonet type fitting, it was a popular type of connection for smaller networks. It's limitations were that on each segment of a network, you could only have 35 PC's or a maximum length of 350 meters of cable. This is due to the degradation of the signal as it gets further along the line. PC's using this connection needed a `T' connector attached to the BNC socket, The maximum speed of the connection was around 10mips. The PC at each end of the segment required a terminator, on the open end of the `T'. This type has rapidly passed out of favour.

A ISA `Combo' card having from left to right, BNC, AUI and UTP connections

UTP

Unified Twisted Pair, is probably the most common type of connection currently in use. It uses a telephone like connector. And can run at 100MIPS (Million Instructions Per Seconds). The common topology for this connection is `Star' topology, where lines to individual PC's fan out from a `Hub' (Fig 7 - 2). UTP can be used to connect two PC's together, using a `reversed' UTP lead.

A UTP ethernet card

USB

Recently it has become possible to network PC using USB. Each machine will need a network adaptor. The hub is a standard USB hub used to connect peripherals such as printers.

A USB network

Wireless

Wireless networking is the easist form of networking for the home user, and assuming that you already have the broadband connection, a new PC can be connected in minuets.

A fully wireless network, probably the best solution for the 'minimalist' who dosen't want cables everywhere, however some (me) would argue that it's not as secure as a cabled network.

FDDI

Glass Fibre interface cards are not as yet that common, this may be in part due to their cost, with an average card costing £500.00+. They are capable of speeds faster than 100mips, but are to an extent waiting for technology to catch up with them.

FDDI cards tend to be used to connect (over glass links) different servers, or sites, using specific FDDI routers and bridges.

Hubs and Bridges

A hub is a box allowing many PC's to connect to the same `backbone' or single line, which may be connected to either another hub, or in the case of a WAN a bridge.

Bridges are devices which form a `bridge' between two sites, one at each end of the line. This link is invariably over a high speed, usually glass fibre line, owned by a telecom company.

A 24 port hub

Network Configurations

There are several different configurations for setting up a networks operating system. The most common for the smaller user, being `Peer to Peer'

A typical Peer to Peer Network may consist of a number of PC's, each of which performs workstation functions, while being available for file access, or sharing peripherals, such as printers (fig 7 -4)