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WCMP message structure
The message structure of WCMP messages varies based on the type of wireless
bearer used by the originator or the message, as well as the type of the WCAMP
message. However, every WCMP does adhere to a general format, as defined in
Figure 18-10.
Bit/Octet 0 1 2 3 4 5 6 7
1 Type of control message
2 Code of control message
3-n Data fields for WCMP (0...n octets)
Figure 18-10 General WCMP message structure
18.9.4 Wireless Transaction Protocol (WTP)
The Wireless Transaction Protocol, defined in the OMA
WAP-224-WTP-20010710-a specification, provides a mechanism especially
designed for WAP terminals with limited resources over networks and with low to
medium bandwidth. This technology allows more subscribers on the same
network due to reduced bandwidth utilization.
WTP provides unreliable and reliable data transfer based on the request/reply
paradigm. Unlike TCP, there is no connection setup and tear down. Compared to
TCP, where a SYN and ACK flow is started before the first data is transmitted,
WTP carries data in the first packet of the protocol exchange. Additionally, WTP
employs a message-oriented model, as opposed to TCP’s stream-oriented
implementation.
WTP classes of operation
There are three classes of operation, numbering zero through two.
Class 0
Class 0 is defined by the OMA specification as “unconfirmed invoke message
with no result message.” This is a datagram that can be sent within the context of
an existing WSP session (see 18.9.5, “Wireless Session Protocol (WSP)” on
page 682). However, it is not intended to be a primary method of sending
Chapter 18. Wireless Application Protocol 679