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WAP 1.1 Architecture

The Wireless Application Protocol (WAP) Version 1.1 defines specifications for the communication with wireless devices, like mobile phones or personal digital assistants (PDAs). The specifications of the protocol are based on existing Internet and network technologies and extend or optimize them for the use in a wireless environment.





Above figure shows the usual infrastructure for a connection from a wireless WAP-enabled device to a standard Internet HTTP server. WAP protocols are used between the WAP client and WAP gateway. Between the WAP gateway and the HTTP server, TCP/IP and HTTP are used. It is the responsibility of the WAP gateway to translate requests from the WAP protocol stack to the WWW protocol stack (TCP/IP and HTTP) and to decode requests sent from the WAP client to the server. The responses from the server are encoded by the gateway into a compact binary format, which the client is able to interpret.
The WAE (Wireless Application Environment) User Agent uses WML (Wireless Markup Language) as the format to display the content. The WAP gateway transforms the HTML documents received from the server into WML in case the server does not provides WML.
WAP 1.1 uses a layered model similar to the ISO OSI Reference Model. On top of the bearers, which are not in the scope of WAP, the WAP Forum has defined protocols for the following layers.
WAE
The Wireless Application Environment (WAE) is the top-most level in the WAP architecture. It is based on WWW and Mobile Telephony technologies. The primary objective of the WAE is to provide the operators and service providers an interoperable environment on which they can build applications and services which, in turn, can be used in a wide variety of hand-held client terminals. WAE includes the micro-browser that contains functionality for using not only WML and WML Script as previously stated, but also Wireless Telephony Application, namely (WTA and WTAI) -telephony services and programming interfaces as well as content formats including well-defined data formats, images, phone book records and calendar information.
WSP
The Wireless Session Protocol (WSP) layer provides a lightweight session layer to allow efficient exchange of data between applications. It provides a connection-oriented service on top of WTP. In addition, it provides a second connection-less service that is based on WDP. WSP currently supports service for browsing, like HTTP 1.1 functionality and semantics in a compact format for wireless connections, long-lived session state, session suspend and resume with session migration, and protocol negotiation. Data push will come with WAP 1.2.
WTP
The Wireless Transaction Protocol operates efficiently over either secure or non-secure wireless datagram networks. It provides three different kinds of transaction services, namely unreliable one-way, reliable one-way and reliable two-way transactions. This layer also includes optional user-to-user reliability by triggering the confirmation of each received message. To reduce the number of messages sent, the feature of delaying acknowledgements can be used.
WTLS
The Wireless Transport Layer Security protocol is based on Transport Layer Security (TLS) or formely known as Secure Sockets Layer (SSL). It is designed to be used with other WAP protocols and to support narrow-band networks. It uses data encryption with a method that is negotiated at the start of the session to provide privacy, data integrity, authentication and denial-of-service protection. The latter is needed in cases when data is replayed or not properly verified. When that happens, WTLS detects the misuse and rejects the data in order to make many typical denial-of-service attacks harder to accomplish.
WDP
The Wireless Datagram Protocol is the transport layer that sends and receives messages via any available bearer network, including SMS, USSD, CSD, and GPRS. The bearer services, over which WAP is designed to operate, include short message, circuit-switched data and packet data services. Since the bearers offer different types of quality of service with respect to throughput, error rate and delays, the WDP is designed to either compensate for or tolerate these changes. Also, WDP lists all the bearers that are supported and the techniques applied when transmitting data over a certain bearer. These lists will change with new bearers being added as the wireless market grows.
Resource Used:
Principles of Mobile Computing
Uwe Hansmann
Lothar Merk
Martin S. Nicklous
Thomas Stober

Posted By: Chaudhary Amit V.


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