ISBN: 0-471-41405 -0
Download (direct link):
Another solution is to use some kind of middleware that takes care of some of the problems for you, as we will describe in Chapter 8, “Adapting for Wireless Challenges.” All together, the most important thing is to be aware of the potential problems and adjust the application accordingly, because these protocols will not change overnight.
Although lots of content will be tailored to the mobile Internet, a substantial part of the existing Internet will also be accessed via wireless networks. The TCP/IP protocol suite was designed a long time ago and is not optimized for the properties of wireless links and consequently does not perform well. Many of the problems that are associated with the existing protocols can, however, be avoided by being aware of the issues and by making the design decisions accordingly.
The Wireless Application Protocol (WAP)
he Wireless Application Protocol (WAP) has become the de facto standard for delivering and presenting information on small, wireless devices. Most people have now seen what WAP looks like and how it feels, but few know how it really works. Initially, there was a lot of hype surrounding WAP, and then there was a predictable backlash (no, WAP will not end world famine). WAP does not do everything that some fancy commercials show (replacing your desktop, offering virtual reality, and so on), but even in its early incarnations, WAP is not as bad as some pessimists indicated (WAP is not crap).
This chapter will not focus on Wireless Markup Language (WML) (although we will describe it briefly). Rather, we will give an extensive overview of how WAP really works and what it does to cope with the properties of wireless networks.
Background and History______________________________________________________________________________
As we have now seen, there are some problems with using existing Internet technologies with wireless networks. Although these protocols are constantly evolving and will be widely used in the future, a number of companies wanted improvements for wireless use quicker than what the Internet Engineering Task Force (IETF) could provide. In the beginning, there were few early incarnations of presentation protocols for wireless.
Nokia worked on smart messaging and the Tagged Text Markup Language (TTML), which it used on its Nokia Communicator. This solution was Nokia -specific, however, and only described GSM/SMS networks.
Unwired Planet (now called Phone.com/Openwave) had developed HDML, an HTML-like markup language for mobile devices. This language was not based on Extensible Markup Language (XML), and the protocol stack was not layered and flexible. Some U.S. operators (AT&T, Sprint, and so on) started with HDML and migrated to pure WAP in order to comply with the international de facto standard. HDML and WML are similar, but making applications that work perfectly with both is not easy. HDML will therefore be phased out gradually.
The Ericsson-developed ITTP was not a Web-based model; rather, it was a platform for phone services. ITTP was not aligned with the appropriate Internet standards and lacked many elements that were needed for a complete presentation framework for mobile devices. WAP’s Wireless Telephony Applications (WTA) cover most of ITTP’s functionality today.
All of these solutions lacked flexibility and functionality, were proprietary, and were not closely aligned with corresponding Internet standards. This situation led Ericsson, Motorola, Nokia, and Unwired Planet to join forces and work on a common standard: WAP. The standardization body formed in June 1997 and was named the WAP Forum, and other companies were invited to join. Due to the $25,000 registration fee, however, member count for the WAP forum is not as great as the Bluetooth Special Interest Group (SIG). As of late 2000, there were some 500 WAP Forum members. Still, all of the important players in the telecommunications and software industries are now members (including Microsoft). The standardization is performed in work groups, each having different areas of responsibility. Every year, there are a number of meetings where discussions surrounding specific issues take place. As the work proceeds, more and more time is spent coordinating efforts with the World Wide Web Consortium (W3C) in order to ensure compatibility between WAP and the protocols of the Internet. WAP already uses existing Internet protocols (IP, UDP, HTTP, and so on) and standards wherever there are competitive solutions available.
The WAP Forum consists of members from various companies in the industry and does not create any products itself. Instead, it licenses the technology on a royalty -free basis and drives the evolution of WAP into an even better standard. Today, it not only develops its own standards but also contributes to the work of other standardization bodies such as 3GPP, W3C, and TIA. In addition, the WAP Forum has developed a framework for the certification of WAP-compliant devices.