A proxy server is a computer that services requests from its client computers by forwarding client requests to the outside servers and also acting as a gateway to any incoming data from an external server. Client computers will usually have to go through the proxy server while requesting a web page, a file or some other resource that is located on a remote server. The proxy will then connect to the specified server and act on behalf of the requesting client. Depending on security settings and other restrictions that have been into place, the server may alter a request that has been made to a remote server. On the other hand it may also alter the response of the remote server, before forwarding it to the client. At other times it may need to contact the remote server in order to service a request. In such a case, the proxy will act as a cache server by storing previously accessed web pages and resources so that when they are requested later on, they can be retrieved much faster.
The most common types of proxy servers are gateways. A gateway is a type of proxy server that handles data coming across a number of platforms that are running on different protocols. Also called protocol converters, these gateways pass unmodified replies and requests between outside servers and clients and can be placed at various points on a local area network as well as across the internet. On the internet, gateways convert packets formatted in one protocol like TCP/IP to another format like AppleTalk before sending it to a client computer. Gateways can either be hardware or software. In most cases however, they are implemented by having software in a router.
In order for a proxy server to act as a gateway they must understand the protocols they are going to handle. Gateways will usually be network points that separate one network from another. Commonly referred to as nodes on the internet, a gateway node acts as the end-point of one network and the beginning of another. Gateways are commonly installed between networks in a company or by internet service providers to their clients. To improve security, gateways will also server as firewall servers by having software installed on them. Most proxies will have 2 IP addresses, one that serves the local area network and the other serving the wide area network like the internet. When properly configured, these proxies ensure network security and efficiency is maintained.
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