1. WAP Architecture
i. It provides a scalable and extensible environment for application development of mobile
ii. This is achieved using layered design of protocol stack. The layers resemble the layers of OSI model.
iii. Each layer is accessible by layers above as well as by other services and applications through a set of well defined interface.
iv. External applications may access session, transaction, security and transport layers directly.
Fig3. WAP Architecture
2. Wireless Application Environment
i. WAE is the uppermost layer in the WAP stack. It is general purpose environment based on combination of WWW and mobile telephony technologies.
ii. Its primary objective is to achieve interoperable environment that allows operators and service providers to build applications that can reach wide variety of wireless platforms.
iii. It uses URL and URI for addressing. Language used is WML and WML script. WML script can be used for validation of user input.
3. Wireless Telephony Application
i. WTA provides a means to create telephony services using WAP. It uses WTA Interface (WTAI) which can be evoked from WML and for WML script.
ii. The Repository makes it possible to store WTA services in device which can be accessed without accessing the network. The access can be based on any event like call disconnect, call answer etc.
iii. Sometimes, there can be notification to user based on which WTA services are accessed by users. The notification is called WTA service indication.
4. Wireless Session Protocol.
i. WSP provides reliable, organized exchange of content between client and server.
ii. The core of WSP design is binary form of HTTP. All methods defined by HTTP 1.1 are supported.
iii. Capability negotiation is used to agree on common level of protocol functionality as well as to agree on a set of extended request methods so that full compatibility to HTTP applications can be retained.
iv. An idle session can be suspended to free network resources and can be resumed without overload of full-blown session establishment.
v. WSP also supports asynchronous requests. Hence, multiple requests will improve utilization of air time.
5. Wireless Transaction Protocol
i. WTP is defined as light-weight transaction-oriented protocol suitable for implementation in thin clients.
ii. Each transaction has unique identifiers, acknowledgements, duplicates removal and retransmission.
iii. Class 1 and Class 2 enable user to confirm every received message, however, in class 0, there is no acknowledgement.
iv. WTP has no security mechanisms and no explicit connection set-up or tear-down phases.
6. Wireless Transport Layer Security
i. WTLS is security protocol based on industry standard transport layer security (TLS). It provides transport layer security between a WAP client and the WAP Gateway/ Proxy.
ii. The goals of WTLS are data integrity, privacy, authentication, Denial-of-service protection.
iii. It has features like datagram support, optimized handshake and dynamic key refreshing.
7. Wireless Datagram Protocol
i. WDP provides application addressing by port numbers, optional segmentation and reassembly, optional error detection.
ii. It supports simultaneous communication instances from higher layer over a single underlying WDP bearer service. The port number identifies higher level entity above WDP.
iii. The adaptation layer of WDP maps WDP functions directly on to a bearer based on its specific characteristics.
iv. On the GSM SMS, datagram functionality is provided by WDP.
8. Optimal WAP Bearers
i. The WAP is designed to operate over a variety of different service like SMS,’ Circuit Switched Data (CSD)’, GPRS,’ Unstructured Supplementary Services Data(USSD)’.