In an enterprise that uses the Internet, a proxy server is a server that acts as an intermediary between a workstation user and the Internet so that the enterprise can ensure security, administrative control, and caching service. A proxy server is associated with or part of a gateway server that separates the enterprise network from the outside network and a firewall server that protects the enterprise network from outside intrusion.
A proxy server receives a request for an Internet service (such as a Web page request) from a user. If it passes filtering requirements, the proxy server, assuming it is also a cache server , looks in its local cache of previously downloaded Web pages. If it finds the page, it returns it to the user without needing to forward the request to the Internet. If the page is not in the cache, the proxy server, acting as a client on behalf of the user, uses one of its own IP addresses to request the page from the server out on the Internet. When the page is returned, the proxy server relates it to the original request and forwards it on to the user.
A proxy server receives a request for an Internet service (such as a Web page request) from a user. If it passes filtering requirements, the proxy server, assuming it is also a cache server , looks in its local cache of previously downloaded Web pages. If it finds the page, it returns it to the user without needing to forward the request to the Internet. If the page is not in the cache, the proxy server, acting as a client on behalf of the user, uses one of its own IP addresses to request the page from the server out on the Internet. When the page is returned, the proxy server relates it to the original request and forwards it on to the user.
To the user, the proxy server is invisible; all Internet requests and returned responses appear to be directly with the addressed Internet server. (The proxy is not quite invisible; its IP address has to be specified as a configuration option to the browser or other protocol program.)
An advantage of a proxy server is that its cache can serve all users. If one or more Internet sites are frequently requested, these are likely to be in the proxy's cache, which will improve user response time. In fact, there are special servers called cache servers. A proxy can also do logging.
The functions of proxy, firewall, and caching can be in separate server programs or combined in a single package. Different server programs can be in different computers. For example, a proxy server may in the same machine with a firewall server or it may be on a separate server and forward requests through the firewall.
A proxy server, also known as a "proxy" or "application level gateway", is a computer that acts as a gateway between a local network (e.g., all the computers at one company or in one building) and a larger-scale network such as the Internet. Proxy servers provide increased performance and security. In some cases, they monitor employees' use of outside resources.
A proxy server works by intercepting connections between sender and receiver. All incoming data enters through one port and is forwarded to the rest of the network via another port. By blocking direct access between two networks, proxy servers make it much more difficult for hackers to get internal addresses and details of a private network.
Some proxy servers are a group of applications or servers that block common Internet services. For example, an HTTP proxy intercepts web access, and an SMTP proxy intercepts email. A proxy server uses a network addressing scheme to present one organization-wide IP address to the Internet. The server funnels all user requests to the Internet and returns responses to the appropriate users. In addition to restricting access from outside, this mechanism can prevent inside users from reaching specific Internet resources (e.g., certain web sites). A proxy server can also be one of the components of a firewall.
Proxies may also cache web pages. Each time an internal user requests a URL from outside, a temporary copy is stored locally. The next time an internal user requests the same URL, the proxy can serve the local copy instead of retrieving the original across the network, improving performance.
Note: Do not confuse a proxy server with a NAT (Network Address Translation) device. A proxy server connects to, responds to, and receives traffic from the Internet, acting on behalf of the client computer, while a NAT device transparently changes the origination address of traffic coming through it before passing it to the Internet.
For those who understand the OSI (Open System Interconnection) model of networking, the technical difference between a proxy and a NAT is that the proxy server works on the transport layer (layer 4) or higher of the OSI model, whereas a NAT works on the network layer (layer 3).
A proxy server, also known as a "proxy" or "application level gateway", is a computer that acts as a gateway between a local network (e.g., all the computers at one company or in one building) and a larger-scale network such as the Internet. Proxy servers provide increased performance and security. In some cases, they monitor employees' use of outside resources.
A proxy server works by intercepting connections between sender and receiver. All incoming data enters through one port and is forwarded to the rest of the network via another port. By blocking direct access between two networks, proxy servers make it much more difficult for hackers to get internal addresses and details of a private network.
Some proxy servers are a group of applications or servers that block common Internet services. For example, an HTTP proxy intercepts web access, and an SMTP proxy intercepts email. A proxy server uses a network addressing scheme to present one organization-wide IP address to the Internet. The server funnels all user requests to the Internet and returns responses to the appropriate users. In addition to restricting access from outside, this mechanism can prevent inside users from reaching specific Internet resources (e.g., certain web sites). A proxy server can also be one of the components of a firewall.
Proxies may also cache web pages. Each time an internal user requests a URL from outside, a temporary copy is stored locally. The next time an internal user requests the same URL, the proxy can serve the local copy instead of retrieving the original across the network, improving performance.
Note: Do not confuse a proxy server with a NAT (Network Address Translation) device. A proxy server connects to, responds to, and receives traffic from the Internet, acting on behalf of the client computer, while a NAT device transparently changes the origination address of traffic coming through it before passing it to the Internet.
For those who understand the OSI (Open System Interconnection) model of networking, the technical difference between a proxy and a NAT is that the proxy server works on the transport layer (layer 4) or higher of the OSI model, whereas a NAT works on the network layer (layer 3).
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