proxy server


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proxy server

Computing a computer that acts as an intermediary between a client machine and a server, caching information to save access time

proxy server

[′präk·sē ‚sər·vər]
(computer science)
Software for caching and filtering Web content to reduce network traffic on intranets, and for increasing security by filtering content and restricting access.

Proxy Server

(software, security)
Microsoft's proxy server and proxy gateway, designed to provide extensible firewall and network security. Proxy Server is part of BackOffice.

proxy server

(programming, World-Wide Web)
A process providing a cache of items available on other servers which are presumably slower or more expensive to access.

This term is used particularly for a World-Wide Web server which accepts URLs with a special prefix. When it receives a request for such a URL, it strips off the prefix and looks for the resulting URL in its local cache. If found, it returns the document immediately, otherwise it fetches it from the remote server, saves a copy in the cache and returns it to the requester. The cache will usually have an expiry algorithm which flushes documents according to their age, size and access history.

Compare proxy gateway.

proxy server

Also called a "proxy," it is a computer system or router that breaks the connection between sender and receiver. Functioning as a relay between client and server, proxy servers help prevent an attacker from invading a private network and are one of several tools used to build a firewall.

The word proxy means "to act on behalf of another," and a proxy server acts on behalf of the user. All requests from clients to the Internet go to the proxy server first. The proxy evaluates the request, and if allowed, re-establishes it on the outbound side to the Internet. Likewise, responses from the Internet go to the proxy server to be evaluated. The proxy then relays the message to the client. Both client and server think they are communicating with one another, but, in fact, are dealing only with the proxy.

Address Translation and Caching
The proxy server is a dual-homed host with two network interfaces and two IP addresses. The IP address on the outbound side of the proxy is the one the Internet sees, and the address of the machine making the request is hidden to the outside world. Proxies are often used in conjunction with network address translation (NAT), which hides all the IP addresses of the client machines on the internal network. Proxy servers may also cache Web pages, so that the next request for that same page can be obtained much faster locally. See NAT and proxy cache.

Other Proxies
Anonymous proxy servers let users surf the Web and keep their IP address private (see anonymous proxy). Although not specifically called a proxy, Internet e-mail (SMTP) is a similar concept because it forwards mail. Messages are not sent directly from client to client without going through the mail server. Likewise, the Internet's Usenet news system (NNTP) forwards messages to neighboring servers. See firewall.

Application Level and Circuit Level
Proxy servers are available for common Internet services; for example, an HTTP proxy is used for Web access; an FTP proxy is used for file transfers. Such proxies are called "application-level" proxies or "application-level gateways," because they are dedicated to a particular application and protocol and are aware of the content of the packets being sent. A generic proxy, called a "circuit-level" proxy, supports multiple applications. For example, SOCKS is IP-based circuit-level proxy server software that supports TCP and UDP applications (see SOCKS).

Forward and Reverse Proxies
In this definition, the proxy servers are used to hide the details of the clients from the servers and are thus known as "forward proxies." However, they can also reside at the website to hide the details of the servers from the clients (see reverse proxy).


A Proxy Server in a LAN
In this LAN server illustration, the proxy server sits between two routers in what is known as a "demilitarized zone." See DMZ.
References in periodicals archive ?
If the anonymous blogger accesses a proxy server before sending defamatory material to the destination website, there is still a trail, the IP addresses.
Appliance-based Internet access management systems now exist that are far more scalable and combine proxy server functionality with a wide range of other capabilities including content filtering, caching, security applications, and so on.
Furthermore, this newly granted patent is applicable to a variety of computer systems or networks including, but not limited to, firewall systems such as application-level gateways or proxy servers.
Their Internet access is provided and secured by a firewall and three Microsoft Proxy Servers, which sit between the users and the Internet, monitoring and intercepting outbound requests and inbound responses.
This approach also reduces temporary storage needs on the VCB proxy server.
When customers, distributors and partners outside the NCR network try to access the content server, they are sent to the proxy server instead.
Flexibility -- With a proxy server agent, SiteMinder can be used to protect any back end resources being managed by the proxy server.
Nasdaq: VRSO), a global provider of next generation network solutions, announced today the general availability of a Network Abuse Detection feature for its NetSpective[R] enterprise Web filter, which can identify, track, and terminate abusive internet behavior, including utilization of anonymous proxy servers and continued probing of unwanted internet content.
The server platforms, Helmsman SIP Proxy Server and SIP Transit Proxy Server, include key server functions that are required within a Service Providers network, over and above the requirements to conform to IETF RFC2543.
I planned to go with a proxy server from one of the bigger vendors," LeClair says.
VMware Consolidated Backup enables the use of a proxy server to offload backups from the host server, thus optimizing performance of backup operations and eliminating overhead from the host server.
VON -- Ubiquity Software Corporation, a major developer of end-to-end SIP service solutions, today announced the commercial availability of the Helmsman(R) SIP Proxy Server release 2.