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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