Components of the WAP Standard Layers of WAP divided into 3 groups Bearer Adaptation Hides the differences in the signaling and channel protocols used among various wireless networks Service Protocols Higher level protocols for moving application data thro’ wireless network Services include – reliability, security and caching Application Environment Powerful, browser-based Supports content and application portability across various device types, independent of the manufacturer

Bearer Adaptation Network (Bearer) protocols for exchanging info to and from the client device Each Bearer protocol – particular type of n/w infrastructure – which in turn is - particular set of suppliers or regions Most common wireless network infrastructures AMPS – The Advanced Mobile Phone System Analog, Most widely used, North America Uses Geographic cells to separate conversation taking place on the same frequency CDPD – Cellular Digital Packet Data 19.2 Kbps digital packet service Uses free space in a voice network to transmit data, FDM Used in US, Canada

IS-54/IS-136/ANSI-136 (North American TDMA) Used in US, Canada Uses TDM and divides the radio frequency into time slots and allocating them to various calls IS-95, CDMA Developed by Qualcomm for US military during WW II Used in US, Canada and some parts of Asia Spread-spectrum technology – tags each conversation with its own digital sequence GSM – Global System for Mobile Communications Runs in the 800 MHz band Used in Australia, Europe and most of Asia Combines TDM and FDM to be similar to CDMA In US, it operates in different frequencies and are called as DCS 1800, PCS 1900

PDC - Personal Digital Cellular Both telephony and data services Used in Japan Combines TDM and FDM PHS – Personal Handy Phone System Evolution of digital cordless phone technology Used in Japan The Flex Protocol By Motorola Supports one-way paging ReFlex – adds two-way Paging capabilities New stds : EDGE, GPRS, UMTS – greater capacity

Scenario Each n/w provides different level of services, uses packets or circuits, may provide SMS, etc What we need? A network-independent system for delivering contents to devices Solution – WAP – WDP (Wireless Datagram Protocol) Hides the differences between the underlying bearer networks WDP – not a protocol; more of Service Abstraction i.e. an assumed set of capabilities upon which the higher layers of the protocol stack build their function It is a datagram service – point-to-point, doesn’t guarantee reliability, security, ordering or timeliness

Solution – Cont… WDP – a collection of protocols – one for each bearer n/w protocol Application  msg thro’ WAP stack  different WDP protocol invoked If bearer n/w protocol = WDP, it simply uses the bearer If bearer n/ w protocol > WDP, uses the bearer ignoring the extra functionality

Service Protocols(SP) WDP – limiting SPs – provides reliability, security, ordering and timeliness – in a layered fashion – to be used by the application environment SPs – are protocols – i.e. define a set of packet formats and a protocol state machine Designed and implemented independent of bearer n/w Gateway – bridge SPs between two bearers simply by changing the type of WDP adaptation Three SP layers : Wireless Transport Layer Security, Wireless Transaction Protocol Wireless Session Protocol

Wireless Transport Layer Security (WTLS) Modeled after the Transport Layer Security (SSL) Provides authentication Using specially optimized c/s certificates – uses less bandwidth includes data encryption defends against various security attacks including replay attacks Defends against denial-of-service attacks Since it is placed just above the WDP, all the attacks are identified and eliminated quickly, there by reducing the computational resource usage Optional layer

Wireless Session Protocol (WSP) Supports efficient, long-term “conversations” i.e supports a WAP micro-browser on a client device to efficiently communicate over the low-bandwidth, high- latency wireless network Modeled on the HTTP both are semantically same WSP request  WAP gateway  HTTP request HTTP response  WAP gateway  WSP response WAP-enabled web server - directly speak WSP Features that are limitations in HTTP but not in WSP Sessions Modularity Binary encoding