Distributed Cooperative Caching In Social Wireless Networks,.

Distributed Cooperative Caching In Social Wireless Networks,.

WAP -WIRELESS APPLICATION PROTOCOL

The WAP Forum

In 1997, Ericsson, Motorola, Nokia, and Unwired Planet formed the WAP Forum(www.wapforum.org). More than 90 companies in the wireless telecommunications business are members of the WAP Forum. WAP is the standard developed by the WAP Forum, a consortium formed by device manufacturers, service providers, content providers, and  application providers. WAP specifies an application framework and protocols for wireless devices. WAP is a kind of fusion of mobile networking technologies and Internet technologies.

The WAP Forum’s objectives include :

·         To bring Internet content and advanced data services to digital cellular phones and  other wireless terminals.

·          To create an interoperable wireless protocol specification that will work across  differing wireless network technologies.

·          To enable the creation of content and applications that could scale across a wide range of wireless bearer networks and device types.

·         To embrace and extend existing standards and technologies

The key features provided by WAP include :

·         A programming model similar to the Internet

·         Wireless Markup Language(WML)

·         WML Script

·         Wireless Telephony Application(WTA)

·         Optimized protocol stack

The WAP architecture provides a scalable and extensible environment for application  development on mobile communication devices. It achieves this through a layered protocol design, covering protocols at Layer 4 and above. The WAP protocol stack is independent of the underlying network, which could take the form of GSM, CDMA, CDPD, iDEN, etc. Hence, WAP is essentially an application stack specification; it is not network-centric.

Wireless Application Environment(WAE)

Generally, WAE enables a spectrum of applications to be supported over WAP. WAE has two main elements, namely: (a) user agents, and (b) services and formats. The former includes the WML and WTA(Wireless Telephone Application) user agents. The latter consists of WML scripts, image formats, etc. A user agent can take the form of a Web browser. The WML user  agent is responsible for the interpretation of WML and WMLScript. WAP employs the same addressing model as in the Internet, that is, it use Uniformed Resource Locators(URLs). AURL uniquely identifies an available resource. WAP also uses Uniform Resource Identifiers (URIs) to address resources that are not accessed via well-known protocols.

Wireless Session Protocol(WSP)

The WSP provides both connection-oriented and connectionless services. It is optimized for low-bandwidth networks with relatively long latency. WSP is a binary version of HTTP version  1.1, but with the additions of : (a) session migrations, (b) header caching, etc. WAP connection mode allows the establishment of sessions between a client and the WAP gateway or proxy. It  can handle session interruptions as a result of mobility and reestablish session states at a later point in time. Header caching allows better bearer utilization since in HTTP, most of the  requests contain static headers that need to be re-sent again.

Wireless Transaction Protocol(WTP)

WTP is designed for transaction-style communications on wireless devices. In a transaction, users express their intentions and financial commitments to service providers for processing Very often, such transactions demand reliable, fast, and secure communications. WTP is a  lightweight protocol suitable for implementation in thin clients. WTP implements selective  retransmission of lost segments.

Wireless Transport Layer Security(WTLS)

WTLS is needed for WAP to ensure data integrity, privacy, authentication, and protection from denial-of-service. It is based on Transport Layer Security(TLS) 1.0, but optimized for  wireless channels. It provides transport layer security between a WAP client and the WAP gateway/proxy. Digital certificates are used for authentication and non repudiation of server and client. Encryption is also used to enhance the degree of confidentiality.

Wireless Datagram Protocol(WDP)

WDP is the transport layer protocol in WAP. It has the same functionality provided by the  Internet User Datagram Protocol(UDP). Whether WAP uses UDP or WDP, datagram delivery  services are provided by port number functionality and the characteristics of different beare services are hidden from the upper layers. WDP can be extended to provide segmentation and

reassembly functions

Software Engineering

Software Engineering is concerned with

•  Technical processes of software development
•  Software project management
•  Development of tools, methods and theories to support software production
•  Getting results of the required quality within the schedule and budget
•  Often involves making compromises
•  Often adopt a systematic and organized approach
•  Less formal development is particularly appropriate for the development of web-based systems

Software Engineering is important because

•  Individuals and society rely on advanced software systems
•  Produce reliable and trustworthy systems economically and quickly
•  Cheaper in the long run to use software engineering methods and techniques for softwaresystems

Fundamental activities being common to all software processes:

•  Software specification: customers and engineers define software that is to be produced and the constraints on its operation
•  Software development: software is designed and programmed
•  Software validation: software is checked to ensure that it is what the customer requires
•  Software evolution: software is modified to reflect changing customer and market requirements

Software Engineering is related to computer science and systems engineering:

 Computer science

o Concerned with theories and methods

 Software Engineering

o Practical problems of producing software

 Systems engineering

o Aspects of development and evolution of complex systems

o Specifying the system, defining its overall architecture, integrating the different parts to 

create the finished system

General issues that affect many different types of software:

 Heterogeneity

o Operate as distributed systems across networks

o Running on general-purpose computers and mobile phones

o Integrate new software with older legacy systems written in different programming 

languages

o Challenge: build dependable software that is flexible enough to cope with heterogeneity

 Business and social change

o Change existing software and rapidly develop new software

o Traditional software engineering techniques are time consuming

o Goal: reduce time to adapt to changing needs

 Security and trust

o Software is intertwined with all aspects of our lives

o See remote software systems (web page, web service interface)

o Make sure malicious users cannot attack software and information security is 

maintained

Essential attributes of good software

 Maintainability

 Dependability and security

 Efficiency

 Acceptability

Application types

 Stand-alone applications

 Interactive transaction-based applications

 Embedded control systems

 Batch processing systems

 Entertainment systems

 Systems for modeling and simulation

 Data collection systems