Wireless Application Protocol

“Wireless application protocol (WAP) is an application environment and set of

communication protocols for wireless devices designed to enable access to the Internet

and advanced telephony services to the wireless community. “

Definition of WAP

What is WAP ?

WAP – The Wireless Application Protocol – Makes it possible to access the Internet via wireless devices such

as mobile phones, PDAs etc.

– Set of rules governing transmission/reception of data by wireless devices (e.g. mobile phones)

Objectives of WAP

Initial focus on wireless phones– Low bandwidth, high latency, low connection stability

To provide Internet access for wireless devices Device & Network Independent To create Wireless Application Environment

– Micro-browser, e-mail, www, mobile to fax access etc.

– WML and WML script.

Limitations of Internet for Wireless Applications

Traditional Internet applications cannot run on mobile devices because of the following limitations:– Low bandwidth network

– High Latency network

– Limited connection stability

– Small display size

– Limited input facility

– Limited memory

– Limited processing power

Current Constraints of

Less Bandwidth High Latency Less Stable Connections Less Predictable Availability Diverse range of network

standards

Less CPU PowerLess CPU Power

Less Memory and StorageLess Memory and Storage

Restricted Power ConsumptionRestricted Power Consumption

Small / Variable Sized DisplaysSmall / Variable Sized Displays

Variable Input Types Variable Input Types (Keypad, Pen, etc,)(Keypad, Pen, etc,)

Wireless Interfaces:Wireless Interfaces: Mobile Devices:Mobile Devices:

WAP: Main Features

Browser– “Micro browser”, similar to existing web browsers

Markup language– Similar to HTML, adapted to mobile devices

Script language– Similar to Javascript, adapted to mobile devices

Gateway– Transition from wireless to wired world

Server– “Wap/Origin server”, similar to existing web servers

Protocol layers– Transport layer, security layer, session layer etc.

Telephony application interface– Access to telephony functions

Internet Model

HTMLHTTP

TLS/SSLTCP/IP

TLS/SSL: Transport layer security Secure Sockets layer

World-Wide Web Model

CGI, Scripts,Etc.

Content

Web Server

Client

WebBrowser

Request(URL)

Response(Content)

WAP Programming Model

CGI, Scripts,Etc.

Content

Web Server

Client

WAEUserAgent

Request(URL)

Response(Content)

Gateway

EncodersAnd Decoders

EncodedRequest

EncodedResponse

WAP Concept Overview

August 2002

WAP Architecture/Protocol Stack

Web Server

Content

CGIScripts

etc.

WM

L D

ecks

wit

h W

ML

-Scr

ipt

WAP Gateway

WML Encoder

WMLScriptCompiler

Protocol Adapters

Client

WML

WML-Script

WTAI

Etc.

HTTPWSP/WTP

WAP Architecture

Source: WAP Forum

WAP Application Server

Content

ApplicationLogic

WM

L D

ecks

wit

h W

ML

-Scr

ipt

WML Encoder

WMLScriptCompiler

Protocol Adapters

Client

WML

WML-Script

WTAI

Etc.

WSP/WTP

WAP Application Server

Source: WAP Forum

Wireless Telephony Application Interface

15

The WAP Model (cont)Based on Version 30-Apr-1998

WAP Device

- Is used to access WAP applications and content. It might be a PDA, handheld computer.

WAP Client

- Entity that receives content from Internet via a WAP Gateway. This is usually the WAP Browser.

WAP Content/Origin/Application Server

- Element in the network where the information or web/WAP applications resides.

WAP Proxy

- Acts both as a client and as a server in the network.Typically has– Protocol gateway : translates requests from the WAP protocol stack

to WWW protocol stack

– Content encoders and decoders : translate WAP content into compact encoded formats to reduce the size of data over the network

It allows content and applications to be hosted on standard WWW servers and developed using proven WWW technologies such as CGI scripting

WAP Gateway

- Intermediary element used to connect two different types of network. It receives request directly from the clients as if it actually were the origin server that clients want to receive the information form. The clients are usually unaware that they are speaking to the Gateway.

WAP Browser– Software running on the WAP device that interprets the WAP

content arriving from the internet and decides how to display it on WAP device.

WML

WML – Wireless Markup Language formerly called HDML (Handheld Devices Markup Language)

Is a tag language that allows the text portions of Web Pages to be presented on cellular phones and Personal Digital Assistants (PDAs) via wireless access.

WML is used for delivering data to WAP devices, and is HTML- like in its appearance.

An alternative to WML is I-Mode’s cHTML language.

WAP Network Example Web Server

WirelessNetwork

WAPProxy

HTMLFilter

WTAServer

WAPClient

WML

WMLHTML

WAP Architecture

Another look

Key Components• Origin/Web Server• WAP Gateway/Proxy• WAP Protocol Stack• Micro Browser• WML/WML Script• Transcoders• WTA

Source: WAP Forum

WWW Protocol Stack

TCP/IPUDP/IP

TLS - SSL

HTTP

HTMLJava Script

Components of WAP Architecture

Other ServicesAnd Applications

Transport Layer (WDP)

Security Layer (WTLS)

Transaction Layer (WTP)

Session Layer (WSP)

Application Layer (WAE)

GSM CDMA PHS IS-136 CDPD PDC-P FLEX Etc…

Bearers :

WAE Components

Architecture– Application model, Microbrowser, Gateway, Server

User Agents– WML/WTA/Others

– content formats: vCard, vCalendar, Wireless Bitmap, WML, ...

WML– XML-Syntax, based on card stacks, variables, ...

WMLScript– procedural, loops, conditions, ... (similar to JavaScript)

WTA– telephone services, such as call control, text messages, phone

book, ... (accessible from WML/WMLScript)

Proxy (Method/Push)

WAP - reference model and protocols

Bearers (GSM, CDPD, ...)

Security Layer (WTLS)

Session Layer (WSP)

Application Layer (WAE)

Transport Layer (WDP)TCP/IP,UDP/IP,media

SSL/TLS

HTML, Java

HTTP

Internet WAP

WAE comprises WML (Wireless Markup Language), WML Script, WTAI etc.

Transaction Layer (WTP)

additional services and applications

WCMP

A-SAP

S-SAP

TR-SAP

SEC-SAP

T-SAP

T-SAP: Transport layer Service access point SEC-SAP: Security SAP TR-SAP: Transaction SAP S-SAP: Session SAP

Wireless Application Environment (WAE)

General-purpose application environment based on a combination of WWW and mobile telephony technologies.

It defines the user interface on the phone. It contains WML and WTA (Wireless Telephony Application).

Primary objective – interoperable environment.

Wireless Application Environment(Contd.)

WAE includes a micro-browser (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 environment which provides– WML– WML script– WTA– Content formats

Origin Servers

WAE: Logical Model

webserver

other contentserver

Gateway Client

otherWAE

user agents

WMLuser agent

WTAuser agent

Push proxy

encodedrequest

request

encodedresponsewithcontent

responsewithcontent

pushcontent

encodedpushcontent

Method proxy

encoders&

decoders

Wireless Session Protocol (WSP) The WAP session protocol (WSP) layer provides a

lightweight session layer to allow efficient exchange of data between applications.

Application layer with a consistent interface for two session services– Connection-oriented service that operates above

the transaction layer protocol (WTP)– Connectionless service that operates above a

secure or non-secure datagram service (WDP)

Optimized for low-bandwidth bearer networks with long latency

Wireless Transaction Protocol (WTP)

The WAP transaction protocol (WTP) layer provides transaction support, adding reliability to the datagram service provided by WDP.

Light weight transaction-oriented protocol Three classes of transaction services

– Unreliable one-way requests

– Reliable one-way requests

– Reliable two-way request-reply transactions

Wireless Transport Layer Security (WTLS)

Based on industry-standard Transport Layer Security (TLS) protocol

Optimized for use over narrow-band communication channels

Features:– Data integrity

– Privacy

– Authentication

– Denial-of-service protection

Wireless Datagram Protocol (WDP)

The WAP datagram protocol (WDP) is the Transport layer that sends and receives messages via any available bearer network, including SMS, USSD, CSD, packet data, and GPRS.

Operates above the data capable bearer services supported by various network types.

Provides a common interface to the upper layer protocols and hence they function independent of the underlying wireless network.

Bearers

Differing levels of quality of service with respect to throughput, error rate, and delays

WAP protocols are designed to compensate for or tolerate these varying levels of service

WDP specification lists the bearers that are supported and techniques used to allow WAP protocols to run over each bearer

WAP: Network Elements

wireless networkfixed network

WAPproxy

WTAserver

filter/WAPproxyweb

server

filter

PSTN

Internet

Binary WML: binary file format for clients

Binary WML

Binary WML

Binary WML

HTML

HTML

HTML WML

WMLHTML

Source: Schiller

Why is HTTP/HTML not enough?

Big pipe - small pipe syndrome

Wireless network<HTML><HEAD><TITLE>NNN Interactive</TITLE><META HTTP-EQUIV="Refresh" CONTENT="1800, URL=/index.html"></HEAD><BODY BGCOLOR="#FFFFFF" BACKGROUND="/images/9607/bgbar5.gif" LINK="#0A3990" ALINK="#FF0000" VLINK="#FF0000" TEXT="000000" ONLOAD="if(parent.frames.length!=0)top.location='http://nnn.com';"> <A NAME="#top"></A><TABLE WIDTH=599 BORDER="0"><TR ALIGN=LEFT><TD WIDTH=117 VALIGN=TOP ALIGN=LEFT>

<HTML><HEAD><TITLE>NNN Interactive</TITLE><META HTTP-EQUIV="Refresh" CONTENT="1800, URL=/index.html">

Internet<WML><CARD><DO TYPE="ACCEPT"><GO URL="/submit?Name=$N"/></DO>Enter name:<INPUT TYPE="TEXT" KEY="N"/></CARD></WML>

010011010011110110010011011011011101010010011010

Content encoding

HTTP/HTML WAP

Source: WAP Forum