WAP - Wireless Application Protocol


Web Enabled Wireless Phones.  In this webpage we will get into the protocols that focus on web enabled cellular telephone technologies.  WAP - Wireless Application Protocol is a standard developed by a number of wireless phone companies such as Ericsson, Nokia, Phone.com.  This consortium is called the WAP Forum.  The overall goal of the WAP forum is to develop standards that will allow Internet communications and advanced telephone services to be supported on all digital mobile phones and other wireless terminals.

Interface Development.  The Internet is largely based on protocols and standards such as HTTP - Hypertext Transfer Protocol and HTML - Hypertext Markup Language.  WAP requires its own standards that will work in the screen formats, memory and processing capabilities available on phones and other devices.

  • WML - Wireless Markup Language is comparable to HTML but developed to web pages for the tiny screens available on cellular telephones.
  • WMLScript - This is a scripting language, analogous to JavaScript, designed to help deliver web page content dynamically.  It is mostly different from JavaScript in its size and management.  WMLScript relies on a number of techniques to keep script sizes small and efficient.

Architecture.  The WAP standard was devised to make use of as little bandwidth for operating overhead as reasonable.  This helps make it a popular protocol on any network.

The following diagram illustrates the WAP stack.



The overall WAP stack is divided into five layers.  The additional network layer includes technologies beyond the scope of this course.

This stack is quite similar to the OSI Reference Model we have studied elsewhere, but it doesn't exactly parallel.  The most obvious additions are a security and transaction layer.

The acronyms are described in more detail in the following bulleted list.

  • WAE - WAP Application Environment - This is where WML, WMLScript and the WTAI - Wireless Telephony Application Interface are implemented.
  • WSP - WAP Session Protocol - This is a session layer protocol used to exchange data through a series of request/response transactions that are performed at the next lower WTP level.
  • WTP - WAP Transaction Protocol - This ends up being analogous to TCP, but much more efficient.
  • WTLS - WAP Transport Layer Security - This offers an optional layer of security in the transport layer.
  • WDP - WAP Datagram Protocol - This is actually the transport layer which is responsible for transmitting and receiving messages.

WAP Gateways are required to interface with the Internet.  These gateways are usually software located on a mobile operator's server.  These gateways handle requests from a WAP phone.  They do things like the following

  • compile WML into byte code
  • puts things into formats that WAP can understand
  • caches some information to streamline the processes