subject: Connecting a LAN to the Internet [print this page] How is a computer system organized so that many different people in a business can all access the net via a LAN, and what sort of things would be needed in house to be able to do this efficiently? You will also need to determine what each user on the LAN will be allowed to do. For example, can they send and receive e-mail, can they brows the net willy nilly' or will you control access to what's available via the LAN? Will it be a tow-way process with outsiders being able to dial into your site? If so, what about security? Do you have a variety of operating systems on the LAN or do you have just windows 98 or NT, which will be just a little easier to deal with? If you have different communication lines does your ISP provide the facilities for more than one user to use the same account at the same time?
If you try using the same ISP account via two different lines from two different computers at the same time, you will almost certainly be logged off from one of the computer! If you go to the same ISP account via a proxy server, although you can now access only one ISP in a simple system, many people can use the same account as all the requests are now routed down the same ISDN Link. To the ISP it looks as though a single person with the dexterity of superman is using the account. To the company operating the LAN, it's as though you have many different' accounts on the internet all going at the same time!
A proxy server is simply a file server set up to control access to the net from your LAN. It can also control access from outside to the websites, which have been set up internally. A proxy server, together with other equipment like routers and special software is also sometimes known as a firewall, because you can prevent hackers from being able to access you LAN via the internet. Using these methods you can also connect a leased line, a direct connection and an appropriate domain name.
To connect a LAN you will need a domain name and some IP addresses. Getting an appropriate domain name for yourself or your company is not too difficult, but your friendly ISP can usually provide a route to your proxy server, which in turn gets the users on the LAN connected to the net. On the WWW the domain name system actually maps the domain names onto the IP addresses. In this way users can use an alias to locate a company, rather than having to type in some horrible IP address like 183.553.957.545, for example.
As you can see, the IP address is basically four numbers separated by full stops, and this refers to the address of a computer on the internet. It is basically an internet address. The system is such that it is ideal the server (which is set up with the appropriate domain name) has received the information, the IP address can be used to route the information to various LANs around the site, and to various computers in an individual LAN. It is the job of the network administrator given the knowledge of a site's network topology.
The simplest way to connect the internet to a LAN is to have what's called a router. This is basically a piece of hardware which connects to your ISDN line at one end and has an Ethernet connection at the other end. More sophisticated routers can handle more versatile connections to a different number of LANs as the needs of your business.
