20.2 Background


20.2 Background

The WAP architecture provides a scalable and extensible environment for application development for mobile communications devices. This is achieved through a layered design of the entire protocol stack. Security in the WAP architecture should enable services to be extended over potentially mobile networks while also preserving the integrity of user data. Figure 20.1 summarizes the WAP as a series of layers. [5]

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Figure 20.1: WAP protocol stack.

The Wireless Application Layer (WAE) is most likely concerned with the deployment of WAP applications. The Wireless Session Protocol (WSP) provides a consistent interface to WAE for two types of session services: a connection mode and a connectionless service. When providing connection mode, the WSP utilizes the Wireless Transaction Protocol layer. In the case of connectionless mode, the WSP takes the advantage of the Wireless Datagram Protocol layer.

Wireless Transaction Protocol (WTP) provides transaction services to WAP. It manages different classes of transactions for WAP devices: unreliable one-way requests, reliable one-way requests, and reliable two-way requests. Wireless Datagram Protocol (WDP) provides a consistent interface to the higher layers of the WAP architecture so that they need not concern themselves with the exact type of wireless network the application is running on. Among other capabilities, WDP provides data error correction. Bearers or wireless communication networks are at the WAP's lowest level. Additionally, each layer is allowed to interact with the layer above and below it.

According to WAP specifications, WTLS is composed by the record protocol, which is a layered protocol. The WTLS record protocol accepts the raw data from the upper layers to be transmitted and applies the selected compression and encryption algorithms to the data. Moreover, the record protocol takes care of the data integrity and authentication. Received data is decrypted, verified, and decompressed, and then handed to the higher layers. The record protocol stack is shown in Figure 20.2. The record protocol is divided into four protocols:

  1. Change Cipher Spec Protocol (CCP)

  2. Handshake Protocol (HP)

  3. Alert Protocol (AP)

  4. Wireless Transaction Protocol (WTP)

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Figure 20.2: WTLS architecture.

The change cipher spec is sent to a peer either by the client or the server. When the change cipher spec message arrives, the sender of the message sets the current write state to the pending state, and the receiver also sets the current read state to the pending state. [6] The change cipher spec message is sent during the handshake phase after the security parameters have been agreed on.

Wireless Application Protocol provides a universal open standard for bringing Internet content and advanced services to mobile phones and other wireless devices. Figure 20.3 shows the WAP architecture. Whenever a mobile phone uses WAP, a connection is created via Wireless Session Protocol (WSP) between the mobile phone and the gateway. When the user enters the address of the WAP site, the gateway is sent a request for the device's microbrowser using WAP. [7] The gateway translates the WSP request into a Hypertext Transfer Protocol (HTTP) request and sends it to the appropriate origin server (or Web server). The Web server then sends back the requested information to the gateway via HTTP. Finally, the gateway translates and compresses the information, which can then be sent back to the microbrowser in the mobile phone.

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Figure 20.3: WAP architecture.

The mobile computing environment is a collection of mobile units (MU) and a fixed networking system. [8], [9] A mobile unit is a mobile computer that varies in size, processing power, and memory, and is capable of connecting to the fixed network via a wireless link. A fixed host is a computer in the fixed network, which is not capable of connecting to a mobile unit. A base station is capable of connecting with a mobile unit and is equipped with a wireless interface. They are known also as mobile support stations (MSS). Base stations, therefore, act as the interface between mobile computers and stationed computers. Each MSS can communicate with MUs that are within its coverage area (a cell). Mobile units can move within a cell or between cells, effectively disconnecting from one MSS and connecting to another. At any point in time, an MU can be connected to only one MSS.

Mobile databases are gaining popularity and are likely to do quite well in coming years as portable devices become increasingly popular. The databases are connected to MSS via the fixed network and wireless digital communications networks. The architecture of the mobile database system [10] is shown in Figure 20.4. Many new database applications require data from a variety of preexisting databases located in various geographical locations. Users of mobile computers may frequently query databases by invoking a series of operations, generally referred to as a transaction.

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Figure 20.4: Mobile database system architecture.

[5]Liang, J. et al., Research on WAP clients supports SET payment protocol, IEEE Wireless Commun., 1 (1), 90–95, February 2002.

[6]Radhamani, G. et al., Security issues in WAP WTLS protocol, IEEE Int. Conf. Commun. Circuits Syst., 483–487, July 2002.

[7]Komnini, N. and Honary, B., Modified WAP for secure voice and video communication, IEEE 2nd Int. Conf. 3G Mobile Commun. Technol., pp. 33–37, 2001.

[8]Lim, J.B., Hurson, A.R., and Ravi, K.M., Concurrent data access in mobile heterogeneous systems, Hawaii Conference on System Sciences, pp. 1–10, 1999.

[9]Dirckze, R.A. and Gruenwald, L., Nomadic transaction management, IEEE Potentials, 17 (2), 31–33, 1998.

[10]Chung, I. et al., Efficient Cache Management Protocol Based on Data Locality in Mobile DBMSs, Springer-Verlag, LNCS 1884, pp. 51–64, 2000.




Wireless Internet Handbook. Technologies, Standards and Applications
Wireless Internet Handbook: Technologies, Standards, and Applications (Internet and Communications)
ISBN: 0849315026
EAN: 2147483647
Year: 2003
Pages: 239

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