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Wireless Application Protocol (WAP) is a technical standard for accessing information over a mobile wireless network. A WAP browser is a web browser for mobile devices such as mobile phones that uses the protocol.
The Japanese i-mode system offers another major competing wireless data protocol.
|This section does not cite any references or sources. (November 2010)|
|The OSI model|
|7 Application layer|
|6 Presentation layer|
|5 Session layer|
|4 Transport layer|
|3 Network layer|
|2 Data link layer|
|1 Physical layer|
|Wireless Application Environment (WAE)||WAP protocol suite|
|Wireless Session Protocol (WSP)|
|Wireless Transaction Protocol (WTP)|
|Wireless Transport Layer Security (WTLS)|
|Wireless Datagram Protocol (WDP)|
|*** Any Wireless Data Network ***|
The bottom-most protocol in the suite, the WAP Datagram Protocol (WDP), functions as 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). All the upper layers view WDP as one and the 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) adapted to the wireless world. WTP supports more effectively than TCP the problem of packet loss, which occurs commonly in 2G wireless technologies in most radio conditions, but is misinterpreted by TCP as network congestion.
The WAE space defines application-specific markup languages.
WAP Push was 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 was specified on top of WAP Datagram Protocol (WDP); as such, it can be delivered over any WDP-supported bearer, such as GPRS or SMS. Most GSM networks have a wide range of modified processors, but 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. This is also known as WAP Push SI (Service Indication). A variant, known as WAP Push SL (Service Loading), directly opens the browser to display the WAP content, without user interaction. Since this behaviour raises security concerns, some handsets handle WAP Push SL messages in the same way as SI, by providing user interaction.
A re-engineered 2.0 version was released in 2002. It uses a cut-down version of XHTML with end-to-end HTTP, dropping the gateway and custom protocol suite used to communicate with it. A WAP gateway can be used in conjunction with WAP 2.0; however, in this scenario, it is used as a standard proxy server. The WAP gateway's role would then shift from one of translation to adding additional information to each request. This would be configured by the operator and could include telephone numbers, location, billing information, and handset information.
Mobile devices process XHTML Mobile Profile (XHTML MP), the markup language defined in WAP 2.0. 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.
Marketers hyped WAP at the time of its introduction, leading users to expect WAP to have the performance of fixed (non-mobile) Internet access. BT Cellnet, one of the UK telecoms, ran an advertising campaign depicting 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 when the first handsets became available in 1999. This led to the wide usage of sardonic phrases such as "Worthless Application Protocol", "Wait And Pay", and so on.
Between 2003 and 2004 WAP 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 were generated by transfer of GPRS and UMTS data, which is a different business model than that used by the traditional Web sites and ISPs. According to the Mobile Data Association, WAP traffic in the UK doubled from 2003 to 2004.
Unlike in Europe, 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 SoftBank Mobile (previously Vodafone Japan) have both successfully deployed WAP technology. In particular, (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.
The adoption of WAP in the US suffered because many cell phone providers required separate activation and additional fees for data support, and also because telecommunications companies have sought to limit data access to only approved data providers operating under license of the signal carrier.
In recognition of the problem, the U.S. Federal Communications Commission (FCC) issued an order on 31 July 2007 which mandated that licensees of the 22-megahertz wide "Upper 700 MHz C Block" spectrum will have to implement a wireless platform which allows customers, device manufacturers, third-party application developers, and others to use any device or application of their choice when operating on this particular licensed network band.[dead link] 
Spin-off technologies, such as Multimedia Messaging Service (MMS), 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 become more device-specific rather aiming at a lowest common denominator, allowed for more usable and compelling content. As a result, the adoption rate of WAP technology is rising.
Commentators have criticized several aspects of Wireless Markup Language (WML) and WAP. Technical criticisms include:
Other criticisms address the wireless carriers' particular implementations of WAP:
The original WAP model provided a simple platform for access to web-like WML services and e-mail using mobile phones in Europe and the SE Asian regions. As of 2009[update] it continues with a considerable user base. The later versions of WAP, primarily targeting the United States market, were designed[by whom?] for a different requirement - to enable full web XHTML access using mobile devices with a higher specification and cost, and with a higher degree of software complexity.
Considerable discussion has addressed the question whether the WAP protocol design was appropriate. Some[who?] have suggested that the bandwidth-sparing simple interface of Gopher would be a better match for mobile phones and Personal digital assistants (PDAs).
The initial design of WAP 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 the inadequacy of TCP over high-packet-loss networks.