WAP Architecture - Wireless Transaction Protocol

Wireless transaction protocol (WTP) does not have security mechanisms. WTP has been defined as a light-weight transaction-oriented protocol that is suitable for implementation in � thin � clients and operates efficiently over wireless datagram networks. Reliability is improved through the use of unique transaction identifi ers, acknowledgments, duplicate removal, and retransmissions. There is an optional user-to-user reliability function in which WTP user can confirm every received message. The last acknowledgment of the transaction, which may contain out-of-band information related to the transaction, is also optional. WTP has no explicit connection set-up or tear-down phases. This improves efficiency over connection-oriented services. The protocol provides mechanisms to minimize the number of transactions being replayed as a result of duplicate packets. WTP is designed for services oriented toward transactions, such as browsing. The basic unit of interchange is an entire message and not a stream of bytes. Concatenation may be used,
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