Components of the WAP StandardLayers of WAP divided into 3 groups

Bearer Adaptation Hides the differences in the signaling and channel

protocols used among various wireless networksService Protocols

Higher level protocols for moving application data thro’ wireless network

Services include – reliability, security and cachingApplication Environment

Powerful, browser-based Supports content and application portability across

various device types, independent of the manufacturer

Bearer AdaptationNetwork (Bearer) protocols for exchanging info to and from

the client deviceEach Bearer protocol – particular type of n/w

infrastructure – which in turn is - particular set of suppliers or regions

Most common wireless network infrastructuresAMPS – The Advanced Mobile Phone System

Analog , Most widely used, North America Uses Geographic cells to separate conversation taking

place on the same frequencyCDPD – 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, CanadaUses TDM and divides the radio frequency into time

slots and allocating them to various calls

IS-95, CDMADeveloped by Qualcomm for US military during WW IIUsed in US, Canada and some parts of AsiaSpread-spectrum technology – tags each conversation

with its own digital sequence

GSM – Global System for Mobile CommunicationsRuns in the 800 MHz band Used in Australia, Europe and most of AsiaCombines TDM and FDM to be similar to CDMAIn US, it operates in different frequencies and are called

as DCS 1800, PCS 1900

PDC - Personal Digital CellularBoth telephony and data servicesUsed in JapanCombines TDM and FDM

PHS – Personal Handy Phone SystemEvolution of digital cordless phone technologyUsed in Japan

The Flex ProtocolBy MotorolaSupports one-way pagingReFlex – adds two-way Paging capabilities

New stds : EDGE, GPRS, UMTS – greater capacity

ScenarioEach n/w provides different level of services, uses

packets or circuits, may provide SMS, etcWhat we need?

A network-independent system for delivering contents to devices

Solution – WAP – WDP (Wireless Datagram Protocol)Hides the differences between the underlying bearer

networksWDP – not a protocol; more of Service Abstractioni.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 protocolApplication msg thro’ WAP stack different

WDP protocol invokedIf bearer n/w protocol = WDP, it simply uses

the bearerIf bearer n/ w protocol > WDP, uses the

bearer ignoring the extra functionality

Service Protocols(SP)WDP – limitingSPs – 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 attacksDefends against denial-of-service attacksSince 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 1.1 - both are semantically same

WSP request WAP gateway HTTP requestHTTP response WAP gateway WSP responseWAP-enabled web server - directly speak WSPFeatures that are limitations in HTTP but not in

WSP Sessions Modularity Binary encoding