马叔叔吉他谱大全打包:Proxy, Forward proxies, Open proxies, Reverse proxy

In computer networks, a proxy server is a server (a computer system or an application) that acts as an intermediary for requests from clients seeking resources from other servers. A client connects to the proxy server, requesting some service, such as a file, connection, web page, or other resource, available from a different server. The proxy server evaluates the request according to its filtering rules. For example, it may filter traffic by IP address or protocol. If the request is validated by the filter, the proxy provides the resource by connecting to the relevant server and requesting the service on behalf of the client. A proxy server may optionally alter the client's request or the server's response, and sometimes it may serve the request without contacting the specified server. In this case, it 'caches' responses from the remote server, and returns subsequent requests for the same content directly.
Communication between two computers (shown in grey) connected through a third computer (shown in red) acting as a proxy.

The proxy concept was invented in the early days of distributed systems^[1] as a way to simplify and control their complexity. Today, most proxies are a web proxy, allowing access to content on the World Wide Web.

Forward proxiesA forward proxy taking requests from an internal network and forwarding them to the Internet.

Forward proxies are proxies where the client server names the target server to connect to.^[5] Forward proxies are able to retrieve from a wide range of sources (in most cases anywhere on the Internet).

The terms "forward proxy" and "forwarding proxy" are a general description of behavior (forwarding traffic) and thus ambiguous. Except for Reverse proxy, the types of proxies described on this article are more specialized sub-types of the general forward proxy concept.

[edit] Open proxies

An open proxy forwarding requests from and to anywhere on the Internet.Main article: Open proxy

An open proxy is a forwarding proxy server that is accessible by any Internet user. Gordon Lyon estimates there are "hundreds of thousands" of open proxies on the Internet.^[6] An anonymous open proxy allows users to conceal their IP address while browsing the Web or using other Internet services.

[edit] Reverse proxies

A reverse proxy taking requests from the Internet and forwarding them to servers in an internal network. Those making requests connect to the proxy and may not be aware of the internal network.Main article: Reverse proxy

A reverse proxy is a proxy server that appears to clients to be an ordinary server. Requests are forwarded to one or more origin servers which handle the request. The response is returned as if it came directly from the proxy server.^[5]

Reverse proxies are installed in the neighborhood of one or more web servers. All traffic coming from the Internet and with a destination of one of the web servers goes through the proxy server. The use of "reverse" originates in its counterpart "forward proxy" since the reverse proxy sits closer to the web server and serves only a restricted set of websites.

In computer networks, a reverse proxy is a type of proxy server that retrieves resources on behalf of a client from one or more servers. These resources are then returned to the client as though it originated from the reverse proxy itself.^[1] While a forward proxy is usually situated between the client application (such as a web browser) and the server(s) hosting the desired resources, a reverse proxy is usually situated closer to the server(s) and will only return a configured set of resources.