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The Web Proxy Auto-Discovery Protocol (WPAD) is a method used by clients to locate the URL of a configuration file using DHCP and/or DNS discovery methods. Once detection and download of the configuration file is complete, it can be executed to determine the proxy for a specified URL. The WPAD protocol only outlines the mechanism for discovering the location of this file, but the most commonly deployed configuration file format is the proxy auto-config format originally designed by Netscape in 1996 for Netscape Navigator 2.0. The WPAD protocol was drafted by a consortium of companies including Inktomi Corporation, Microsoft Corporation, RealNetworks, Inc., and Sun Microsystems, Inc. (now Oracle Corp.). WPAD is documented in an INTERNET-DRAFT which expired in December 1999. However, WPAD is still supported by all major browsers.〔(【引用サイトリンク】 title=Chromium #18575: Non-Windows platforms: WPAD (proxy autodetect discovery) does not test DHCP )〕〔(【引用サイトリンク】 title=Firefox #356831 - Proxy autodiscovery doesn't check DHCP (option 252 )〕 WPAD was first included with Internet Explorer 5.0. == Context == In order for all browsers in an organization to be supplied the same proxy policy, without configuring each browser manually, both the below technologies are required: * Proxy auto-config (PAC) standard: create and publish one central proxy configuration file. Details are discussed in a separate article. * Web Proxy Autodiscovery Protocol (WPAD) standard: ensure that an organization's browsers will find this file without manual configuration. This is the topic of this article. The WPAD standard defines two alternative methods the system administrator can use to publish the location of the proxy configuration file, using the Dynamic Host Configuration Protocol (DHCP) or the Domain Name System (DNS): Before fetching its first page, a web browser implementing this method sends the local DHCP server a DHCPINFORM query, and uses the URL from the WPAD option in the server's reply. If the DHCP server does not provide the desired information, DNS is used. If, for example, the network name of the user's computer is ''pc.department.branch.example.com'', the browser will try the following URLs in turn until it finds a proxy configuration file within the domain of the client: * * * * (Note: These are examples and are not "live" URLs due to them employing the reserved domain name of "example.com".) Additionally if the DNS query is unsuccessful then LLMNR will be used. Additionally if the DNS query is unsuccessful then NetBios will be used.〔(【引用サイトリンク】 title=Troubleshooting Web Proxy Auto Discovery (WPAD) issues )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Web Proxy Autodiscovery Protocol」の詳細全文を読む スポンサード リンク
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