WAP will provide multiple applications, for business and customer markets such as banking, corporate database access, and a messaging interface (see Figure 2).

Figure 2. Messaging Interface

The request from the mobile device is sent as a URL through the operator's network to the WAP gateway, which is the interface between the operator's network and the Internet (see Figure 3).
Figure 3. Architecture of the WAP Gateway

WDP
The WAP datagram protocol (WDP) is the transport layer that sends and receives messages via any available bearer network, including SMS, USSD, CSD, CDPD, IS–136 packet data, and GPRS.

WTLS
Wireless transport layer security (WTLS), an optional security layer, has encryption facilities that provide the secure transport service required by many applications, such as e-commerce.

WTP
The WAP transaction protocol (WTP) layer provides transaction support, adding reliability to the datagram service provided by WDP.

WSP
The WAP session protocol (WSP) layer provides a lightweight session layer to allow efficient exchange of data between applications.

HTTP Interface
The HTTP interface serves to retrieve WAP content from the Internet requested by the mobile device.

WAP content (WML and WMLScript) is converted into a compact binary form for transmission over the air (see Figure 4).

Figure 4. WAP Content in Compact Binary Form

The WAP microbrowser software within the mobile device interprets the byte code and displays the interactive WAP content (see Figure 5).

Figure 5. Mobile Device Display