ECommerce Technology

ECommerce >> Networks

Networks

 A network is basically the interconnection of related parts, grouping them together in common functionality. It is a system of lines or channels that cross or interconnect various points, called nodes. These nodes can be stations on a rail network, or cities connected by roads. We make us of networks everyday, the telephone network being another example.

 Computer networks are the same in principle to that of all other networks, in that they interconnect computers and other peripherals, as opposed to cites or stations.

LANs

 Computers, when interconnected in this way, in the same geographical region, are called Local Area Networks (LANs). These networks usually belong to a single company or organisation, and occupy the same building or campus.

The diagram below shows a company LAN that has mini LANs in each department with their own server machine. Each mini LAN is connected to a central hub/switch, which also facilitates the connection of the main server. In a situation such as this, each department would have their own hardware and software requirements controlled by their own local server. This prevents the main server and the network over all, from becoming congested, thus improving performance. The technique is known as sub-netting.

 WANs

Wide Area Networks (WANs) are the interconnection of multiple networks spread over a much wider graphical region. This can be across a city, country, continent or even the entire globe. In order to facilitate the connection of these smaller networks to each other, the use of a communication infrastructure is sought. A telecommunications company like Mercury or BT, to mention only two, provides the services for such connections, albeit at a price.

Communication Infrastructures

There are various technologies available, each varying in performance and cost.

 PSTN

The cheapest by far is the public systems telephone network (PSTN). This is the same media that carries telephone conversations, and in terms of performance, though workable for the home user, is not a viable commercial solution. It has a bandwidth of 56Kbps using compression techniques, however, due to various environmental factors like line quality and control features, this capacity is theoretical. Access to this medium is acquired through the use of a device called a modem. A modem connects the PC to the phone line and acts as an analogue to digital converter.

 IDSN

ISDN (Integrated Services Digital Network) is a faster more reliable solution, that makes use of a fibre optic transmission media (cable). The key features of ISDN are:

· High bit-rate - an ISDN channel has throughput of 64Kbps ·

All digital interfaces - no need for analogue to digital conversion equipment (modems) ·

Very fast call set-up time as opposed to 30 seconds for modem connections

· Supports digitised voice and digital data.

ISDN comes in two flavours to UK subscribers.

ISDN2 - This solution offers 2x64Kpbs channels (called B channels) and one 16Kpbs channel used or control purposes. Under certain circumstances it is possible to use the control channel (called the D Channel) to carry data, providing a total of 144Kpbs

ISDN30 - This solution provides 30B channels, allowing for a total cable capacity of 2Mbps, depending on the amount of channels in use at any one time. As each channel is brought into use the greater the capacity, but also the greater the cost.

xDSL

The latest in digital solutions, come in the form the xDSL (x Digital Subscriber Line) range, and is a more likely solution for the business user. xDSL, like ISDN, it is an always-on system eliminating the need for dial-up. xDSL comes in several flavours. Depending on location and requirements, one of the following should be considered:

Cable

At 512Kbps cable boasts even greater speeds than some of xDSL applications. This type of Internet connectivity uses coaxial cable, the same cable that carriers TV pictures into the home. The PC is connected to the cable box via a length of cable going into the PC's network card (for home users).

When these services are enlisted, it is important to understand, that although the connection behaves like it is a dedicated link between the two entities, it, in fact is not. The data is routed through many switching boxes and over many different cable segments, before it reaches its destination (see PPTP diagram).