Patent ID: 7545818

Claim:
A method of switching a first gateway from a voice mode to a facsimile mode, said method comprising: configuring said first gateway to said voice mode for communication with a second gateway over a packet network; receiving a plurality of UDP data packets from said second gateway over said packet network; analyzing one or more of said plurality of UDP data packets to determine whether said one or more of said plurality of UDP data packets carry facsimile UDPTL data packets or voice RTP data packets, wherein said analyzing includes comparing an RTP type field within each UDP payload with a predetermined RTP type, and determining that said one or more of said plurality of UDP data packets do not carry facsimile UDPTL data packets if said RTP type field within each UDP payload does not match said predetermined RTP type; and configuring said first gateway to said facsimile mode if said analyzing determines that said one of more of said plurality of UDP data packets carry facsimile UDPTL data packets; wherein each UDP packet includes a UDP header and a UDP payload, said UDP header indicates a first length of said UDP payload, each UDPTL packet has a predetermined structure, and wherein said analyzing comprises: calculating a second length of said UDP payload in accordance with said predetermined structure of said UDPTL packet; and deciding said UDP payload includes said UDPTL packet if said first length is equal to said second length.