Wireless Application Protocol

As you learn about Microsoft Mobile Information 2001 Server, you'll benefit from some familiarity with the Wireless Application Protocol (WAP) standard, a key enabling technology for delivering wireless solutions. Fundamentally, WAP is a set of protocols that covers Open System Interconnection (OSI) layers 3 through 7 and that closely resembles traditional Internet protocols such as HTTP and Secure Sockets Layer (SSL).

Designed specifically for wireless networks' low bandwidth and high latency, WAP provides a platform for delivering wireless applications that are optimized for the small displays, limited memory, and restricted input capability and processing power of wireless devices such as mobile phones. A key advantage of WAP that's especially relevant in the US market is that WAP is bearer-independent. Hence, WAP applications, coupled with appropriate WAP-enabled devices, work over Global System for Mobile Communication (GSM), Code Division Multiple Access (CDMA), Cellular Digital Packet Data (CDPD), and any other network type.

WAP consists of several protocols. One of those protocols, Wireless Markup Language (WML), is worth a mention here. Mobile Information Server's built-in Outlook Mobile Access uses WML to deliver browse functionality.

In the future, WML, as well as HTML and other markup languages, will come together into Extensible HTML (XHTML), a markup language suitable for writing applications that can be rendered for any device type—wired or wireless. Thus, XHTML will let developers use one code base to develop applications for all client types. Developers can use WML with any dynamic Web technology, such as Common Gateway Interface (CGI) or Active Server Pages (ASP), to deliver dynamic WML functionality and content. Advanced WML techniques let developers use Extensible Style Language Transformations (XSLT) and an XML parser to transform data from XML data sources into WML content. Such techniques can translate XML data into other markup languages and customize the data to different client types. The only real differences between WAP and Web applications are that WAP applications use WML instead of HTML as the markup language and WAP applications use a different MIME type (i.e., text/vnd.wap.wml) than Web applications do.

Until late 2000, no true WAP services or devices were available in the US market. Most of the wireless technology being deployed in the United States uses pre-WAP Handheld Device Markup Language (HDML) and the associated Openwave UP.Link Server gateway. WAP gateways translate protocols between wireless and wired networks by translating between WAP- and HTTP-based protocols. WAP gateways also encode wireless content into binary format to optimize delivery over wireless networks. You can expect to see many true WAP products and services being released into the US market in 2001. For more information about WAP, see Tao Zhou, "Going Wireless," Spring 2001, or visit http://www.wapforum.org.

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