This Recommendation defines a package that allows the media gateway controller (MGC) to specify the nominal value and the minimum value of the adaptive jitter buffer on the media gateway (MG). This package allows the MGC to specify adaptive jitter buffer value settings on a particular stream at any time throughout a call, and it allows the MGC to enable or disable the use of a jitter buffer. In addition, the package contains a set of jitter buffer metrics that are consistent with those described in IETF RFC 3611, RTP Control Protocol Extended Reports (RTCP XR). These jitter buffer metrics may be used, for example, with voice over IP, video, and audio. The package should be used in combination with the base network package that defines the maximum value for the jitter buffer. An adaptive jitter buffer (AJB) is characterized by these minimum, maximum, and nominal values.
The AJB functions in a MG to smooth the play out of packets arriving at the MG. As the packet arrival delay varies during the course of the transmission, the jitter buffer adapts using the minimum, maximum, and nominal values to control the adaptation. Real time media requirements are stringent and, for that reason, it is important to set the jitter buffer values to their optimal setting as early on the call as possible since a jitter buffer that is too large will introduce unnecessary bearer delay, which has a negative impact on real time media quality, and a jitter buffer that is too small will prevent a smooth play out (packet loss, another negative impact). The proper jitter buffer size is the balance between delay and packet loss. The distortion that the media receiver would otherwise observe is eliminated with the AJB.