Web Proxy Autodiscovery Protocol

Web Proxy Auto-Discovery Protocol(WPAD) is a method in which the client uses DHCP and DNS discovery methods to locate the URL of a configuration file. once the configuration file is detected and downloaded, the configuration file will be executed to determine the Proxy that a URL should use. the WPAD protocol only describes the mechanism for finding the location of the configuration file.

Most of the deployed configuration files are in the format of Proxy auto-config, which was first designed by Netscape for Netscape Navigator 1996 in 2.0.

For the first time, the WPAD protocol exists in IE in Internet Explorer 5.0.

Application

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In order to allow all browsers of a company to have a unified proxy policy, rather than manually configuring each browser, we need the following two technologies

• Proxy auto-config (PAC) Standard: Creates and releases a central Proxy configuration file.
• Web Proxy Autodiscovery Protocol (WPADStandard: Make sure that the configuration file can be found in the organization's browser without manual configuration.

The WPAD standard defines two methods that can be selected by the system administrator to publish the location of the agent configuration file.

• Dynamic Host Configuration Protocol (DHCP)
• Domain Name System (DNS)

Before obtaining the page, the browser implementing this method will send a DHCPINFORM query to the local DHCP server, and then use the URL in the WPAD option returned by the server. if the DHCP server does not provide the required information, DNS is used.

For example, the FQDN of a computer isPc.department.branch.example.comThen, the browser on this machine will use the following URL in sequence to find the proxy configuration file in the domain:

Http://wpad.department.branch.example.com/wpad.dat

Http://wpad.branch.example.com/wpad.dat

Http://wpad.example.com/wpad.dat

Http://wpad.com/wpad.dat (in incorrect implementations, see note in Security below)

IE

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The configuration here is WPAD.

Translated from:

Web Proxy Autodiscovery Protocol

Http://en.wikipedia.org/wiki/Web_Proxy_Autodiscovery_Protocol