sequenced data with poll PDU (ATM) (SDP-PDU)
The Sequenced Data with Poll PDU( SDP-PDU) is one of 16 protocol data units (PDU) of the Service Specific Connection Oriented Protocol( SSCOP), which is the service specific convergence sublayer( SSCS) of the AAL layer for signaling channels in ATM networks.
The SDP PDU or POLL PDU is the protocol data unit that requests status information from the opposite side.