Protocol design lessons from WAP The original WAP was a simple platform for access to web-like WML services and e-mail using mobile phones in Europe and the SE Asian regions and continues today with a considerable user base. The later versions of WAP were primarily for the United States region and was designed 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. There has been considerable discussion about whether the WAP protocol design was appropriate. Some have suggested that the bandwidth-sparing simple interface of Gopher would be a better match for mobile phones and Personal digital assistants (PDAs).[19] 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 the inadequacy of TCP over high packet loss networks. WAP 2.0 WAP 2.0 released in 2002 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). 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. XHTML Mobile Profile (XHTML MP), 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. The WAP Forum was founded in 1997. The forum’s main aim was to bring together the various wireless technologies by a standardised protocol. In 2002 the WAP Forum was 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 1.X The WAP 1.0 standard was released in April 1998 and described a complete software stack for mobile internet access.WAP version 1.1 was released in 1999.[5]. WAP 1.2, the final update of the 1.X series was released in June 2000.[6]. The most important addition in version 1.2 was WAP push.WAP Push WAP Push Process WAP Push has been incorporated into the pecification 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.[9] In most GSM networks there are 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).The network entity that processes WAP Pushes and delivers them over an IP or SMS Bearer is known as a Push Proxy Gateway (PPG). |
Tuesday, September 20, 2011
WAP
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