Methods and apparatus are disclosed for changing the bandwidth or other traffic characteristic of an established packet call in response to an identification of the requirements of the call. In response to the detection of a type of call, such as a fax or modem call, ATM signaling is performed with peer signaling agent(s) located in the ATM network to increase the bandwidth of an already established portion of a call through the ATM network. This signaling typically includes sending a call modify request message and receiving a modify acknowledgement message, with these messages typically, but not limited to, conforming with a Q.2963 signaling standard.