Wireless Application Environment or WAE:
The Wireless Application Environment, or WAE,
provides an architecture for communication between wireless devices and Web
servers. To understand WAE, you should first be familiar with the World Wide
Web (WWW) model, which is a simpler architecture based on similar
principles.
In the WWW model, a browser requests a URL from a Web server via HTTP. That Web
server responds with an HTML page, which is also sent via HTTP. Because all
browsers speak HTTP and both client and server speak the same protocol, they can
communicate directly.
Hardware and Software Requirement:
At minimum developing WAP applications requires a web server and a WAP
simulator. Using simulator software while developing a WAP application is
convenient as all the required software can be installed on the development PC.
Although, software simulators are good in their own right, no WAP application
should go into production without testing it with actual hardware. The following
list gives a quick overview of the necessary hardware and software to test and
develop WAP applications:
A web server with connection to the Internet
A WML to develop WAP application
A WAP simulator to test WAP application
A WAP gateway
A WAP phone for final testing.
Microsoft IIS or Apache on Windows or Linux can be used as the web server and
Nokia WAP Toolkit version 2.0 as the WAP simulator.
Environment of WAE:
WTLS(Wireless Transport Layer Security):
Wireless Transport Layer Security is a protocol based on the TLS protocol. It is
used with the WAP transport protocols and has been optimised for use over
narrow-band communication channels. The WTLs layer is above the transport
protocol layer. The required security layer of the protocol determines whether
it is used or not. It provides a secure transport service interface that
preserves the transport service interface below; additionally it provides an
interface for managing secure connections. WTLS aims to provide privacy, data
integrity and authentication between two communication applications. Among its
features are datagram support, optimised handshaking and dynamic key refreshing.
It is optimised for low-bandwidth bearer networks with relatively long latency.
The WTLS Record Protocol is a layered protocol. The Record Protocol takes
messages to be transmitted, optionally compresses the data, applies a MAC,
encrypts, and transmits the result. Received data is decrypted, verified, and
decompressed, then delivered to higher-level clients. Four record protocol
clients are described in the WTLS standard; the change cipher spec protocol, the
handshake protocol, the alert protocol and the application data protocol. If a
WTLS implementation receives a record type it does not understand, it ignores
it. Several records can be concatenated into one transport SDU. For example,
several handshake messages can be transmitted in one transport SDU. This is
particularly useful with packet-oriented transports such as GSM short messages.
WTP( Wireless Transaction Protocol):
The Wireless Transaction Protocol provides the services necessary for
interactive browsing applications. During a browsing session the client requests
information from a server and the server responds with the information. This is
referred to as a transaction. WTP runs on a datagram service and possible a
security service.
Advantages of WTP include:
Improved reliability over datagram services
Imported efficiency over connection oriented services
As a message oriented protocol, it is designed for services oriented towards
transactions.
3 kinds of transaction services.
Class 0 Unreliable invoke messages with no result messages
Class 1: Reliable invoke messages with no result messages
Class 2: Reliable invoke messages with exactly one reliable result
message.
Reliability achieved by using unique transaction identifiers, acknowledgements,
duplicate removal; and retransmissions.
No explicit set up or tear down phases.
Optional user-to-user reliability.
Optionally the last acknowledgement of the transaction may contain out-of-band
information.
Concatenation may be used to convey multiple PDUs in one service data unit of
the datagram transport.
The basic unit of interchange is an entire message, not a stream of bytes.
Mechanisms are provided to minimize the number of transactions replayed as a
result of duplicate packets.
Abort of outstanding transactions.
For reliable invoke messages, both success and failure reported.
Asynchronous transactions allowed.
WSP(Wireless Session Protocol):
The Session layer protocol family in the WAP architecture is called the Wireless
Session Protocol, WSP. WSP provides the upper-level application layer of WAP
with a consistent interface for two session services. The first is a
connection-mode service that operates above a transaction layer protocol WTP,
and the second is a connectionless service that operates above a secure or
non-secure datagram transport service.
The Wireless Session Protocols currently offer services most suited for browsing
applications. WSP provides HTTP 1.1 functionality (it is a binary form of HTTP)
and incorporates new features such as long-lived sessions, a common facility for
data push, capability negotiation and session suspend/resume. The protocols in
the WSP family are optimized for low-bandwidth bearer networks with relatively
long latency. Requests and responses can include both headers and data. WSP
provides push and pull data transfer WSP functions on the transaction and
datagram services.
Messages can be in connection mode or connectionless. Connection mode messages
are carried over WTP. In this case the protocol consists of WTP protocol
messages with WSP PDUs as their data. Connectionless messages consist only of
the WSP PDUs.