AT&T will end the contract of any of its customers caught using peer-to-peer (P2P) software on mobile phones, the operator told the FCC.

Robert Quinn Jr., senior vice president in charge of federal regulation issues, wrote in a public letter to the FCC that “AT&T does not use network management tools to block the use of P2P applications by its mobile wireless broadband customers. However, AT&T’s terms of service for mobile wireless broadband customers prohibit all uses that may cause extreme network capacity issues, and explicitly identify P2P file sharing applications as such a use… use of a P2P file sharing application would constitute a material breach of contract for which the user’s service could be terminated.”

However, “AT&T has not yet found it necessary to terminate anyone’s service for such a use,” he added.

Quinn argued in his letter that all major U.S. carriers have similar policies.  But none have been so specific and public about their intentions to terminate customer contracts.  A copy of the letter is posted on the blog at IP Democracy.

The decision is not without good reasons, he said.  The letter explains: “Today’s P2P file-sharing applications are inappropriate for AT&T’s mobile wireless broadband network, which is optimized to efficiently support high data rates for multiple users that send and receive intermittent or ‘bursty’ traffic generated by activities such as browsing the Internet and sending email. Because P2P file sharing applications typically engage in continuous (rather than bursty) transmissions at high data rates, a small number of users of P2P file sharing applications served by a particular cell site could severely degrade the service quality enjoyed by all customers served by that site.”

It continues, “Moreover, unlike wired broadband networks where the maximum number of potential simultaneous users in a given neighborhood is known in advance, the maximum number of potential mobile wireless broadband users that may simultaneously seek to access a given cell site at any particular time – and thus the collective service experience for all users at that site, for both data and voice services – is far less predictable due to the inherently nomadic nature of mobile wireless users.”

Industry analyst firm Techdirt, in its company blog, noted that AT&T will have a bigger problem if Apple certifies any P2P application for the iPhone, which is exclusively sold in the United States by AT&T.