Abstract: A network device has a port to allow the device to transmit text telephony packets over a packet network. The device includes at least one processor to detect impending buffer overflow, determine a number of text telephony characters to be dropped, and select a compression to be applied to the text telephony characters to manage buffer overflow.

Abstract: In a gateway router the length of the play-out buffer in VBD mode is not set at a previously established value. Instead the length of the play-out buffer in VBD mode is determined by the length of the buffer in the previous audio mode. When the system switches from audio mode to VDB mode, the length of the play-out buffer in audio mode is noted. The length of the play-out buffer in VBD mode is then set equal to its length in the prior audio mode plus a dilation factor. An audio concealment algorithm (which fills in gaps caused by missed packets) is used during the transition from audio to VDB to conceal any transition glitch during the answer tone.

Abstract: A method for compensating for asynchronous clock sources is presented. A buffer is provided for storing frames received from a packet network. The buffer having a preselected playout delay. Upon detecting a buffer overflow, a drain operation is performed on the buffer and the playout delay is modified to provide a sufficient number of buffer locations for frames to be stored. Upon detecting a buffer underflow, a fill operation is performed on the buffer and the playout delay is modified to provide a sufficient number of frames to be played out.