14-06-2012, 05:39 PM
Wireless Application Protocol
Wireless Application Protocol.ppt (Size: 329.5 KB / Downloads: 31)
Wireless Application Protocol (WAP)
Open standard providing mobile users of wireless terminals access to telephony and information services including the internet and the web.
Wireless terminals include wireless phones, pagers and personal digital assistants (PDAs)
Designed to work with all wireless network technologies such as GSM, CDMA, and TDMA
Based on existing Internet standards such as IP, XML, HTML, and HTTP
Includes security facilities
WAP is designed to deal with
Limited capabilities of mobile devices and still provide ease of use
Low data rates of the digital networks.
The WAP specification includes
A programming model, A markup languages (WML adhering to XML)
A specification of small browser for mobile, wireless terminals
A lightweight communication protocol stack
A f/w for wireless telephony applications (WTA’s)
WAP is designed to deal with
The mobile devices have limited memory, processors & battery life
The user interface is also limited, displays small
Wireless networks have relatively low bandwidth, high latency, unpredictable availability
Features vary from network to network and terminal to terminal.
Mobile terminals must be extremely easy to use
WAP elements
Using WAP a mobile user can browse Web content on an ordinary Web server
Web server provides content in the form of HTML-coded pages that are transmitted using HTTP/TCP/IP.
HTML content must go through an HTML filter
Filter translates the HTML content inti WML content
If the filter is separate from the proxy, HTTP/TCP/IP is used to deliver the WML to the proxy.
Proxy converts WML to binary WML
Wireless Markup Language (WML) Features
WML was designed to describe content and format for presenting data on devices with limited bandwidth, screen size, input capability
WAE
Provides for an addressing model for accessing both the WWW URLs and other resources specific to the wireless domain
Use WML as the standard markup language, which can be constructed from an efficient binary encoded form of the traditional HTML
Provides compact scripting language analogous to JAVASCRIPT
Provides a set of telephony applications
WSP
WSP establishes a reliable session between the client and the server ,session release
WSP provied equivalent of HTTP in the WWW domain
The core of the WSP design is a binary form of HTTP.
Wireless Session Protocol (WSP)
Transaction-oriented protocol based on the concept of a request and a reply
Provides applications with interface for two session services:
Connection-oriented session service – operates above reliable transport protocol WTP
Connectionless session service – operates above unreliable transport protocol WDP
The principal limitations addressed in WSP are low data rate and susceptibility to loss of connection due to poor coverage or cell overloading
WSP is a transaction oriented protocol based on the concept of request and reply.
Each WSP PDU consists of a body, which may contain WML, WMLScript, or images, and a header, which contain information about the data in the body and about the transaction.
WSP May contain server push operation – broadcast messages or for services such as news headlines, stock quotes
Connection-mode WSP Services
Establish reliable session from client to server and release
Agree on common level of protocol functionality using capability negotiation
Exchange content between client and server using compact encoding
Suspend and resume a session
Push content from server to client in an unsynchronized manner
WSP Transaction Types
Session establishment – client WSP user requests session with server WSP user
Session termination – client WSP user initiates termination
Session suspend and resume – initiated with suspend and resume requests
Transaction – exchange of data between a client and server
Nonconfirmed data push – used to send unsolicited information from server to client
Confirmed data push – server receives delivery confirmation from client
Wireless Transaction Protocol (WTP)
WTP Manages transactions by conveying requests and responses between a user agent (WAP Browser) and an application server for such activities as browsing and e-commerce transactions
Lightweight protocol suitable for "thin" clients and over low-bandwidth wireless links
WTP is a transaction oriented rather than connection oriented (with reliable connectionless service).
WTP features
Three classes of transaction service
Optional user-to-user reliability: WTP user triggers confirmation of each received message
Optional out-of-band data on acknowledgments
PDU concatenation and delayed acknowledgment to reduce the number of messages sent
Asynchronous transactions
WTP Transaction Classes
Class 0: Unreliable invoke message with no result message.
Provides unreliable datagram service, which can be used for unreliable push operation.
Class 1: Reliable invoke message with no result message
Provides reliable datagram service, which can be used for reliable push operation.
Class 2: Unreliable invoke message with one reliable result message
Provides a request / response transaction service and supports the execution of multiple transactions during one WSP session.
Wireless Transport Layer Security (WTLS)
Provides security services between mobile client and the WAP gateway.
WTLS is based on industry standard TLS protocol. TLS is used between web browser and web server.
To provide end-to-end security WTLS is used between the client and the gateway, and TLS is used between the gateway and target server.
WTLS provides following features
Data integrity – ensures that data sent between client and gateway are not modified, using message authentication
Privacy – ensures that the data cannot be read by a third party, using encryption
Authentication – establishes authentication of the two parties, using digital certificates
Denial-of-service protection – detects and rejects messages that are replayed or not successfully verified
Wireless Datagram Protocol (WDP)
Used to adapt higher-layer WAP protocol to the communication mechanism used between mobile node and WAP gateway
WDP hides details of the various bearer networks from the other layers of WAP
Adaptation may include:
Partitioning data into segments of appropriate size for the bearer
Interfacing with the bearer network