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Wireless Application Protocol

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This is an article about the Wireless Application Protocol. WAP can also refer to wireless access points.

WAP is an open international standard for applications that use wireless communication (for example, Internet access from a mobile phone). WAP was designed to provide services equivalent to a web browser with some mobile-specific additions, being specifically designed to address the limitations of very small portable devices. It is now the protocol used for the majority of the world's mobile Internet sites, otherwise known as wap-sites (WAPsites, WAP sites, wapsites, etc.). The Japanese i-mode system is the other major competing wireless data protocol.

Reason for creation

                   WAP is a protocol suite created for mobile devices such as PDAs and mobile phones, aiming at giving their users a richer data application experience that would enable "access to the Internet". Before WAP became popular, it was nearly impossible for application providers to build interactive data applications that would allow, for example, business people on the go to catch an important e-mail or learn early on that they were losing money on their stocks, nor was it possible to build rich data applications allowing consumers to get sports results and the latest news headlines from their TV. WAP was aimed at enabling this type of application to be built with wireless technology.

Technical specifications

WAP protocol suite

The WAP Forum proposed a protocol suite that would allow the interoperability of WAP equipment and software with many different network technologies; the rationale for this was to build a single platform for competing network technologies such as GSM and IS-95 (also known as CDMA) networks. 

 +------------------------------------------+ 
 | Wireless Application Environment (WAE)   |   
 +------------------------------------------+  \
 | Wireless Session Protocol (WSP)          |   |
 +------------------------------------------+   |
 | Wireless Transaction Protocol (WTP)      |   | WAP
 +------------------------------------------+   | protocol
 | Wireless Transport Layer Security (WTLS) |   | suite
 +------------------------------------------+   |
 | Wireless Datagram Protocol (WDP)         |   |
 +------------------------------------------+  /
 |     *** Any wireless data network ***    |
 +------------------------------------------+
  • The bottom-most protocol in the suite is the WAP Datagram Protocol (WDP), which is an adaptation layer that makes every data network look a bit like UDP to the upper layers by providing unreliable transport of data with two 16-bit port numbers (origin and destination). WDP is considered by all the upper layers as one and same protocol, which has several "technical realizations" on top of other "data bearers" such as SMS, USSD, etc. On native IP bearers such as GPRS, UMTS packet-radio service, or PPP on top of a circuit-switched data connection, WDP is in fact exactly UDP.
  • WTP provides transaction support (reliable request/response) that is adapted to the wireless world. WTP supports more effectively than TCP the problem of packet loss, which is common in 2G wireless technologies in most radio conditions, but is misinterpreted by TCP as network congestion.
  • Finally, WSP is best thought of on first approach as a compressed version of HTTP.

This protocol suite allows a terminal to emit requests that have an HTTP or HTTPS equivalent to a WAP "gateway"; the gateway translates requests into plain HTTP.

Wireless Application Environment (WAE)

In this space, application-specific markup languages are defined.

The primary language of the WAE is WML, the Wireless Markup Language, which has been designed from scratch for handheld devices with phone-specific features. WML is an XML-compliant format. However, since XML documents can take up a lot of room, a specific compression technique for XML documents was developed (wireless binary XML, or WBXML).

Maintenance and evolutions

The WAP Forum has consolidated (along with many other forums of the industry) into OMA (Open Mobile Alliance), which covers virtually everything in future development of wireless data services.

WAP 2.0

The new version of WAP, is a re-engineering of WAP using a cut-down version of XHTML with end-to-end HTTP (i.e., dropping the gateway and custom protocol suite used to communicate with it).

Some observers predict that this next-generation WAP will converge with, and be replaced by, true Web access to pocket devices. Whether this next generation (Wireless Internet Protocol to mobile) will still be referred to as WAP is yet to be decided. XHTML MP (XHTML Mobile Profile), the markup language defined in WAP 2.0, is made to work in mobile devices. It is a subset of XHTML and a superset of XHTML Basic. A version of cascading style sheets (CSS) called WAP CSS is supported by XHTML MP.

WAP Push

WAP Push, has been incorporated into the specification to allow WAP content to be pushed to the mobile handset with minimum user intervention. A WAP Push is basically a specially encoded message which includes a link to a WAP address. WAP Push is specified on top of WDP; as such, it can be delivered over any WDP-supported bearer, such as GPRS or SMS.

In most GSM networks, however, GPRS activation from the network is not generally supported, so WAP Push messages have to be delivered on top of the SMS bearer. On receiving a WAP Push, a WAP 1.2 or later enabled handset will automatically give the user the option to access the WAP content.

In this way, the WAP Push directs the end user to a WAP address where particular content may be stored ready for viewing or downloading to the handset. The address could be a simple page or multimedia content (e.g., polyphonic ring tone) or a Java application. Using WAP Push, one can make it easier for end users to discover and access new mobile services.

Commercial status

Possible failure

WAP was hyped at the time of its introduction, leading users to expect WAP to have the performance of the Web. One telco's advertising showed a cartoon WAP user "surfing" through a Neuromancer-like "information space". In terms of speed, ease of use, appearance, and interoperability, the reality fell far short of expectations. This led to the wide usage of sardonic phrases such as "Worthless Application Protocol", "Wait And Pay", and so on.

Critics advanced several explanations for the early failure of WAP. Some are technical criticisms:

  • The idiosyncratic WML language, which cut users off from the true HTML Web, leaving only native WAP content and Web-to-WAP "proxified" content available to WAP users. However, others argue that technology at that stage would simply not have been able to give access to anything but custom-designed content.
  • Under-specification of terminal requirements. In the early WAP "standards", there were many optional features and under-specified requirements, which meant that compliant devices would not necessarily interoperate properly. This resulted in great variability in the actual behavior of phones. As an example, some phone models would not accept a page more than 1 Kb in size; others would downright crash. The user interface of devices was also underspecified: as an example, accesskeys (e.g., the ability to press '4' to access directly the fourth link in a list) were variously implemented depending on phone models (sometimes with the accesskey number automatically displayed by the browser next to the link, sometimes without it, and sometimes accesskeys were not implemented at all).
  • Constrained user interface capabilities. Terminals with small black and white screens and few buttons, as the early WAP terminals were, are not very apt at presenting a lot of information to their user, which compounded the other problems: one would have had to be extra careful in designing the user interface on such a resource-constrained device.
  • Lack of good authoring tools. The problems above might have been alleviated by a WML authoring tool that would have allowed content providers to easily publish content that would interoperate flawlessly with many models, adapting the pages presented to the User-Agent type. However, the development kits which existed did not provide such a general capability. Developing for the web was easy: with a text editor and a web browser, anybody could get started, thanks also to the forgiving nature of most desktop browser rendering engines. By contrast, the stringent requirements of the WML specifications, the variability in terminals, and the demands of testing on various wireless terminals, along with the lack of widely available desktop authoring and emulation tools, considerably lengthened the time required to complete most projects.

Other criticisms are oriented towards the wireless carriers' particular implementations of WAP:

  • Neglect of content providers. Some wireless carriers had assumed a "build it and they will come" strategy, meaning that they would just provide the transport of data as well as the terminals, and then wait for content providers to publish their services on the Internet and make their investment in WAP useful. However, content providers received little help or incentive to go through the complicated route of development. Others, notably in Japan (cf. below), had a more thorough dialogue with their content provider community, which was then replicated in modern, more successful WAP services such as i-mode in Europe or the Gallery service in France.
  • Lack of openness. Most wireless carriers sold their WAP services that were "open", in that they allowed users to reach any service expressed in WML and published on the Internet. However, they also made sure that the first page that clients accessed was their own "wireless portal", which they controlled very closely. Given the difficulty in typing up fully qualified URLs on a phone keyboard, most users would give up going "off portal"; by not letting third parties put their own entries on the operators' wireless portal, some contend that operators cut themselves off from a valuable opportunity. On the other hand, some operators argue that their customers would have wanted them to manage the experience and, on such a constrained device, avoid giving access to too many services.

Possible success

However, WAP has seen huge success in Japan. While the largest operator NTT DoCoMo has famously disdained WAP in favor of its in-house system i-mode, rival operators KDDI (au) and Vodafone Japan have both been successful with the WAP technology. In particular, J-Phone's Sha-Mail picture mail and Java (JSCL) services, as well as au's chakuuta/chakumovie (ringtone song/ringtone movie) services are based on WAP. After being shadowed by the initial success of i-mode, the two smaller Japanese operators have been gaining market share from DoCoMo since spring 2001.

Korea is also leading the world in providing advanced WAP services. WAP on top of the CDMA2000 network has been proven to be the state of the art wireless data infrastructure.

According to the Mobile Data Association, June 2004 has seen a considerable increase of 42% in its recorded number of WAP pages viewed compared with the same period in 2003. This takes the total for the second quarter of 2004 to 4 billion.

Since 2003 and 2004, WAP has made a stronger resurgence with the introduction of Wireless services (such as Vodafone Live!, T-Mobile T-Zones and other easily-accessible services). Operator revenues are generated by transfer of GPRS and UMTS data which is a different model to the Web, and usage is up. People are starting to use WAP and the early failures have been masked, as the real point of the system – access to wireless services and applications – has come to the forefront.

Spin-off technologies, such as MMS (Multimedia Messaging Service) (picture messaging), a combination of WAP and SMS, have further driven the protocol. An enhanced appreciation of device diversity, supported by the concomitant changes to WAP content to be more device-specific rather than being aimed at a lowest common denominator, has allowed for the content presented to be more compelling and usable. As a result, the adoption rate of WAP technology is on the upswing.

Protocol design lessons from WAP

There has been considerable discussion about whether the WAP protocol design was appropriate. The initial design of WAP was specifically aimed at protocol independence across a range of different protocols (SMS, IP over PPP over a circuit switched bearer, IP over GPRS, etc). This has led to a protocol considerably more complex than an approach directly over IP might have caused.

Most controversial, especially for many from the IP side, was the design of WAP over IP. WAP's transmission layer protocol, WTP, uses its own retransmission mechanisms over UDP to attempt to solve the problem of TCP's inadequacy for high packet loss networks.

See also

=== WAP URLs === WAP URLs currently active for use in WAP research and information access.

This article is based on material taken from the Free On-line Dictionary of Computing prior to 1 November 2008 and incorporated under the "relicensing" terms of the GFDL, version 1.3 or later.

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