where applicable, to convey multiple packet data units (PDUs) in one service data unit (SDU) of the datagram transport. WTP allows asynchronous transactions. There are three classes of transaction service:
● Class 0: Unreliable “ send ” with no result message. No retransmission if the sent message is lost.
● Class 1: Reliable “ send ” with no result message. The recipient acknowledges the sent message; otherwise the message is resent.
● Class 2: Reliable “ send ” with exactly one reliable result message. A data request is sent and a result is received which is fi nally acknowledged by the initiating part.
Source of Information : Elsevier Wireless Networking Complete 2010