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P4P, or proactive network provider participation for P2P, is a method for internet service providers (ISPs) and peer-to-peer (P2P) software to optimize peer-to-peer connections. P4P proponents say that it can save an ISP significant costs, and that using local connections also speeds up download times for P2P downloaders by 45%, critics say that this will favor downloaders on some ISPs but come at the expense of others. == Description == Established in 2007,〔http://www.dcia.info/activities/p4pwg/membership.html〕 the P4P Working Group (P4PWG) has participants from the ISP, movie/content, and P2P industries.() It is focused on helping ISPs handle the demands of large media files and enabling legal distribution – they are building what they believe will be a more effective model of transmitting movies and other large files to customers. The current P2P model shares data equally with all peers, regardless of whether they are nearby, and this results in several nearby peers sending and receiving data across the world but not to each other when this is possible – working group members say that currently "the pattern of traffic poses a problem". P4P works by having an ISP use a new "iTracker" which provides information on how the ISP's network is configured. P2P client software (and P2P torrent servers, called trackers) can query the iTracker to identify the data routes the ISP prefers and connections to avoid, changing depending on the time of day. The P2P software can then co-operatively connect to peers which are closer (or cheaper for the ISP), selectively favoring peers instead of choosing peers randomly. This provides three methods of finding local peers: # the P2P client receives network information from the ISP's iTracker without revealing what file is being downloaded. It separately receives a list of peers from the torrent's tracker as usual. Note that for torrents with thousands of peers, when queried only a short list of potential peers is sent and it can take many queries to find all local peers # the torrent's tracker can receive network information from the ISP's P4P iTracker, and use this to provide to the P2P client a customized list of local peers # the P2P client can query the P4P iTracker, providing it with details of the file being downloaded. The ISP's iTracker (instead of the torrent tracker) can then provide the client with a list of local peers Note that P4P does not replace or control P2P networks. P4P allows ISPs to provides additional information regarding network topology that P2P networks may choose to utilize to optimize network data delivery. This information should be used in combination with the other information that P2P networks collect, such as observed peer data transfer rates. If, for example, a P2P network is selecting between a "nearby" peer that is slow, and a "far" peer that is fast, that decision is entirely under the control of the P2P network. Because implementation of P4P is entirely voluntary on the part of both the ISPs and the P2P networks, it will only be adopted if it is mutually beneficial. 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「Proactive network provider participation for P2P」の詳細全文を読む スポンサード リンク
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