Answer to Question #259119 in HTML/JavaScript Web Application for pooja

Question

f) Explain the WAP protocol stack. Explain the following WML elements with the help of an

example:

 Line Break

 Tables in WML

 WML images

Answer 1

The WAP stack consists of the following layers:

 

WAE – WIRELESS APPLICATION ENVIRONMENT

The Wireless Application Environment (WAE) defines the following functions:

 

Wireless Markup Language (WML). 

WML is an XML-based markup language for the visual display of WAP-based contents. Once HTML and WML will converge into XML, many compatibility problems, during conversion from HTML to WML, will cease to exist.

 

WML Script. 

A script language, very similar to JavaScript.

 

Wireless Telephony Application (WTA, WTAI). 

Telephony services and Programming interfaces.

 

Content formats. 

These are specifications for data formats, including images, telephone directories, calendar information, and so on.

 

The WAE corresponds to the application layer in the OSI  model.

 

 

WSP – WIRELESS SESSION PROTOCOL

The Wireless Session Protocol (WSP) implements an interface for connection-oriented and connectionless session services. The connection-oriented session service operates using the protocol of the transaction layer. However, the connectionless session service uses a secure or non-secure datagram service.

 

WSP offers the following basic functions:

- Functions and semantics of HTTP/1.1, using a compact coding scheme

- Pausing and resuming sessions

- A general facility for reliable and unreliable data push

- Negotiation of protocol functions

 

 

 

WTP – WIRELESS TRANSACTION PROTOCOL

The Wireless Transaction Protocol (WTP) is a transaction-oriented protocol, executed using a datagram service. WTP offers the following functions:

 

Three classes of transaction services

(a) Unreliable one-way requests

(b) Reliable one-way requests

(c) Reliable two-way request/response transactions

 

Optional user-to-user reliability feature.

The WTP user triggers confirmation for each received message.     

 

Optional out-of-band data for confirmations.

 

Protocol Data Unit (PDU) chaining and delayed confirmation.

In order to reduce the number of sent messages

 

Asynchronous transactions

 

WTLS – WIRELESS TRANSACTION LAYER SECURITY

The WTLS layer implements a security protocol based on the TLS (Transport Layer Security) industry standard. WTLS is intended for use with the WAP transport protocols and has the following features:

Data integrity – WTLS ensures that the data sent between the terminal and an application server is in no way altered or damaged.      

Confidentiality – WTLS ensures that the data sent between the terminal and an application server remains confidential and cannot be understood by any other participant who may have intercepted the data stream.

Authentication – WTLS ensures the authenticity of the terminal and of the application server.      

Denial-of-service protection – Wireless Transaction Layer Security (WTLS) contains features that will recognize and reject data that has been repeated or not verified successfully. WTLS hinders many typical denial-of-service attacks and protects the upper protocol layers. Though, this is not a perfect solution.

 

WDP – WIRELESS DATAGRAM PROTOCOL

The WDP layer operates on various bearers that depend on the used network

type. WDP offers a consistent interface for the upper layers so that

communications occurs transparently using one of the available bearer services.

Therefore, the transport layer is adapted to the specific functions of the

underlying bearer.