Answer to Question #259123 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.

Wireless Markup Language (WML), based on XML, is a now-obsolete markup language intended for devices that implement the Wireless Application Protocol (WAP) specification, such as mobile phones. It provides navigational support, data input, hyperlinks, text and image presentation, and forms, much like HTML (Hypertext Markup Language). It preceded the use of other markup languages now used with WAP, such as HTML itself, and XHTML (which are gaining in popularity as processing power in mobile devices increases).

line break:

<br/> is the line breaking tag in WML, which is the same as that in HTML

example:

<wml>
  <card id="card1" title="Line Break">
    <p>
      Before br<br/>After br
    </p>
  </card>
</wml>

the text after the <br/> tag starts on a new line

Tables in WML:

• The <table> element along with <tr> and <td> is used to create a table in WML. WML does not allow the nesting of tables
• A <table> element should be put with-in <p>...</p> elements.

example:

<wml>

<card title="WML Tables">
<p>
<table columns="3" align="LCR">
	<tr>
	  <td>Col 1</td>
	  <td>Col 2</td>
	  <td>Col 3</td>
	</tr>

	<tr>
	  <td>A</td>
	  <td>B</td>
	  <td>C</td>
	</tr>

	<tr>
	  <td>D</td>
	  <td>E</td>

	  <td>F</td>
	</tr>
</table>
</p>
</card>

</wml>

result:

WML images:

The <img> element is used to include an image in a WAP card. WAP-enabled wireless devices only supported the Wireless Bitmap (WBMP) image format.

WBMP images can only contain two colors: black and white. The file extension of WBMP is ".wbmp" and the MIME type of WBMP is "image/vnd.wap.wbmp".

example:

<wml>

<card title="WML Images">
<p>
This is Thumb image
<img src="/images/thumb.wbmp" alt="Thumb Image"/>
</p>

<p>
This is Heart image
<img src="/images/heart.wbmp" alt="Heart Image"/>
</p>

</card>

</wml>

result: