Payload header suppression mask defines the bit mask that is used in combination with the docsIetfQosPHSField. It defines which bytes in the header must be suppressed/restored by the sending or receiving device. Each bit of this bit mask corresponds to a byte in the docsIetfQosPHSField, with the least significant bit corresponding to the first byte of the docsIetfQosPHSField. Each bit of the bit mask specifies whether the corresponding byte should be suppressed in the packet. A bit value of '1' indicates that the byte should be suppressed by the sending device and restored by the receiving device. A bit value of '0' indicates that the byte should not be suppressed by the sending device or restored by the receiving device. If the bit mask does not contain a bit for each byte in the docsIetfQosPHSField, then the bit mask is extended with bit values of '1' to be the necessary length.