Speed limiting IP facsimile method and method for realizing speed limit of gate in IP facsmile

A method for limiting bit rate in IP facsimile, in this method the highest bit rate that the called gateway allows is determined, after the call connection is set up, the called fax machine transmits the digital identification containing the highest facsimile bit rate that the called fax machine provides, the called gateway compares the highest facsimile bit rate that the called fax machine provides with the determined highest bit rate that the called gateway allows, then selects the lower and inserts in the frame and transmits to the calling fax machine, the calling fax machine compares the bit rate with the highest bit rate that the calling fax machine itself provides, the lowest will be the highest bit rate at which message is transmitted, then the message is transmitted, confirmed, then the call connection is released. In this method, when the network becomes bad, the highest facsimile bit rate is limited through gateway to improve quality of pictures. A method for achieving limiting bit rate in IP facsimile by a gateway is also proposed in the present invention.