Wireless Application Protocol

INTRODUCTION

The Wireless Application Protocol is a standard developed by WAP Forum, which is a group founded by Ericsson,Nokia, Motorola and Phone.com. Now software companies such as Microsoft, Oracle, IBM, and Intel along with several hundred other companies holds membership in the WAP Forem.



GOALS OF WAP

1. Independent of wireless network standard.


2. Open to all.


3. Proposed to the appropriate standards bodies.


4. Scalable across transport options.


5. Scalable across device types.


6. Extensible over time to new networks and transports.


WAP defines a communication protocol as well as an application environment. In essence, It is a standardized technology for cross-platform, distributed computing. WAP is similar to the World Wide Web.The WAP model closely resembles the Internet model of working. In Internet a WWW client requests a resource stored on a web server by identifying it using a unique URL, that is, a text string constituting an address to that resource. WAP client applications make requests very similar in concept to the URL concept in use on the Web.Standard communication protocols, like HTTP and Transmission Control Protocol/Internet Protocol (TCP/IP) manage these requests and transfer of data between the two ends. The content that is transferred can either be static like html pages or dynamic like Active Server Pages (ASP), Common Gateway Interface (CGI), and Servlets.


WORKING


A WAP request is routed through a WAP gateway which acts as an intermediary between the “bearer” used by the client (GSM, CDMA, TDMA, etc.) and the computing network that the WAP gateway resides on (TCP/IP in most cases). The gateway then processes the request, retrieves contents or calls CGI scripts, Java servlets, or some other dynamic mechanism, then formats data for return to the client. This data is formatted as WML (Wireless Markup Language), a markup language based directly on XML. Once the WML has been prepared (known as a deck), the gateway then sends the completed request back (in binary form due to bandwidth restrictions) to the client for display and/or processing. The client retrieves the first card off of the deck and displays it on the monitor.

The deck of cards metaphor is designed specifically to take advantage of small display areas on handheld devices. Instead of continually requesting and retrieving cards (the WAP equivalent of HTML pages), each client request results in the retrieval of a deck of one or more cards. The client device can employ logic via embedded WMLScript (the WAP equivalent of client-side JavaScript) for intelligently processing these cards and the resultant user inputs.

To sum up, the client makes a request. This request is received by a WAP gateway that then processes the request and formulates a reply using WML. When ready, the WML is sent back to the client for display. As mentioned earlier, this is very similar in concept to the standard stateless HTTP transaction involving client Web browsers.

There are three essential product components that you need to extend your host applications and data to WAP-enabled devices. These three components are:

WAP Microbrowser – residing in the client handheld device


WAP Gateway – typically on wireless ISP’s network infrastructure


WAP Server - residing either on ISP’s infrastructure or on enduser organization’s infrastructure .


WAP Mcrobrowser

A WAP micro-browser is a client software designed to overcome challenges of mobile handheld devices that enables wireless access to services such as Internet information in combination with a suitable network server.

WAP Gateway

WAP Gateway is a piece of software that sits between the mobile device and the external network like the Internet. The gateway does the job of converting Internet content i.e. the WML pages into byte code (WMLC) to reduce the size and number of packets, which can be understood by a WAP device.

A WAP Gateway contains following functionalities

1. Protocol Gateway- The protocol Gateway translates requests from the WAP protocol stack to the WWW protocol stack(HTTP and TCP/IP).

2.Content Encoders and Decoders- The content encoders translate web content into compact encoded formats to reduce the size and number of packets travelling over the wireless data network.


WAP Server

It is simply a combined web server and WAP gateway. WAP devices do not use SSL( secure socket layer protocol-cryptographic protocol that provide security for communications over networks such as the Internet.), instead they use WTLS( a security protocol for wap). Most existing web servers should be able to support WAP content as well. Some new MIME(multipurpose internet mail extentions) types need to be added to your web server to enable it support WAP content. MIME stands for Multipurpose Internet Mail Extension, and in the web context, MIME can be thought of as a piece of header information that comes down with every file sent from a web server to a browser.



FEATURES OF WAP


1. Interoperability: WAP is an open license-free standard, which ensures that WAP-compliant devices are interoperable.

2. Scalability: WAP applications scale across a variety of wireless transport options like GSM SMS, GSM USSD, IP, CDMA, etc., and also across a wide range of wireless terminals from hand sets to powerful PDAs.

3. Extensibility: WAP has been designed as a future-proof technology. It is extensible over time to new networks and transports thereby protecting the mobile network

4. Flexibility: WAP is a flexible solution that caters to the requirements of various types of applications by providing service options like connection mode and connection-less services, with or without end-to-end security.

5. Reusability: WAP specification extends and adapts existing Internet standards such as HTTP, IP, Proxy technology, SSL, TLS, XML, HTML,etc., to wireless environment instead of defining a new set of standards.



ARCHITECTURE


The WAP Protocol Stack is implemented via a layered approach (similar to the OSI network model). These layers consist (from top to bottom) of :


Wireless Application Environment (WAE)- WAE provides a network neutral and device independent application environment framework, which enables a wide range of applications (user-agents) to be used on wireless terminals.


Wireless Session Protocol (WSP)- WSP layer provides mechanisms and semantics based on the Internet standard, Hyper Text Transfer Protocol (HTTP/1.1) along with additional functionalities such as:

1.protocol feature negotiation (capability negotiation)

2. compact encoding of data

3. session suspend/resume

4. long lived session states

5. asynchronous request



Wireless Transaction Protocol (WTP)- WTP layer provides a lightweight transaction service, i.e., a request/response service, which can operate efficiently over a secure, or insecure datagram service.WTP is message oriented protocol, which makes it suitable for interactive browsing applications.



Wireless Transport Layer Security (WTLS)- WTLS( similar to Transport Layer Security TLS used in the internet) was developed to address the problematic issues such as limited processing power and memory capacity, and low bandwidth - and to provide adequate authentication, data integrity, and privacy protection mechanisms.


Wireless Datagram Protocol (WDP)- WDP provides the higher layers of the stack with a consistent interface to underlying bearer. WDP operates transparently over one of the available bearer services there by making the upper layers of the WAP stack independent of the bearer. Since the services offered by underlying bearers vary widely, WDP contains adaptation layers to map WDP functions to services offered by different bearers.


Bearers (GSM, IS-136, CDMA, GPRS, CDPD, etc.)




The WAP stack can be configured in four different ways to provide four different types of services. Following are the four types of services offered by WAP :

1. Connectionless service: The WAP protocol stack used for this service consists of only WSP layer operating directly over WDP layer.

2. Connectionless service with security: This configuration is similar to connectionless service but provides security by having WTLS layer between WSP and WDP layers.

3. Connection oriented service: The configuration of protocol stack used for this service consists of WSP, WTP and WDP layers with ordering of the layers same as that shown in Figure WTP and WDP layers together provide a connection oriented transport service in this configuration.

4.Connection oriented service with security: This configuration consists of all the layers of WAP stack.




CONCLUSION



The primary focus of WAP technology is to create a global wireless internet by bringing services offered by internet to mobile phone users. Industry leaders in handset manufacturing representing over 90% of the world market and mobile network operators representing about 300 million subscribers are adopting this technology. WAP has been designed to benefit wireless subscribers, handset vendors, network operators and service providers. Subscribers get access to a wide range of services available on Internet from their mobile phones and other wireless interoperable open standard, whichis is handset vendor independent. Some critics and second-guessers have pondered the need for a technology. WAP’s use of the deck of cards “pattern” and use of binary file distribution meshes well with the display size and bandwidth constraints of typical wireless devices. Scripting support gives us support for client-side user validation and interaction with the portable device again helping to eliminate round trips to remote servers. WAP is a young technology that is certain to mature as the wireless data industry as a whole matures; however, even as it exists today, it can be used as an extremely powerful tool in every software developer’s toolbox.


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