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| What
is WAP ? Wireless Application Protocol |
Presented by: |  Copyright 2000© |
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Introduction
The wireless telecommunication and the Internet are rapidly growing industries that are gaining more and more customers every day. The WAP intention is to combine these two markets and answer the new demands in this field. These reasons and more driven some of the largest vendors to unite and create the WAP Forum, the standardizing organization of the WAP. (More details at http://www.wapforum.org/)
WAP specifies an application framework and network protocols for wireless devices such as mobile phones, pagers and personal digital assistants. WAPs specifications extend existing mobile networking technologies such as wireless networking standards and extend some Internet technologies such as XML, scripting and content formats.
Wireless hand-held devices preset a more constrained computing environment and platforms, compared to desktop computers which most of the Internet technology was developed for. The hand-held devices tend to have less powerful CPUs, less memory, very restricted power consumption and problematic MMI (smaller and variant displays, phone keypads etc.). Furthermore the wireless networks present greater problems as communication infrastructures they have less bandwidth, more latency and less connection stability and unpredictable availability. WAP intends to overcome these difficulties by being interoperable, have scaleable quality of service, efficient in the mobile network resources, reliable and secure.
Technical Concept Introduction
The WAP programming model is similar to the WWW programming model. This provides several benefits to the application developer community, including a familiar programming model, a proven architecture, and the ability to leverage existing tools (eg, Web servers, XML tools, etc.). Optimisations and extensions have been made in order to match the characteristics of the wireless environment. Wherever possible, existing standards have been adopted or have been used as the starting point for the WAP technology.
WAP content and applications are specified in a set of well-known content formats based on the familiar WWW content formats. Content is transported using a set of standard communication protocols based on the WWW communication protocols. A micro browser in the wireless terminal co-ordinates the user interface and is analogous to a standard web browser.
The following diagram illustrates the concept and architecture of WAP:
WAP defines a set of standard components that enable communication between mobile terminals and network servers, including:
Standard naming model WWW-standard URLs are used to identify WAP content on origin servers. WWW-standard URIs are used to identify local resources in a device, eg call control functions.
Content typing All WAP content is given a specific type consistent with WWW typing. This allows WAP user agents to correctly process the content based on its type.
Standard content formats WAP content formats are based on WWW technology and include display markup, calendar information, electronic business card objects, images and scripting language.
Standard communication protocols WAP communication protocols enable the communication of browser requests from the mobile terminal to the network web server.
The WAP content types and protocols have been optimised for mass market, hand-held wireless devices. WAP utilises proxy technology to connect between the wireless domain and the WWW. The WAP proxy typically is comprised of the following functionality:
Protocol Gateway The protocol gateway translates requests from the WAP protocol stack (WSP, WTP, WTLS, and WDP) to the WWW protocol stack (HTTP and TCP/IP).
Content Encoders and Decoders The content encoders translate WAP content into compact encoded formats to reduce the size of data over the network.
This infrastructure ensures that mobile terminal users can browse a wide variety of WAP content and applications, and that the application author is able to build content services and applications that run on a large base of mobile terminals. The WAP proxy allows content and applications to be hosted on standard WWW servers and to be developed using proven WWW technologies such as CGI scripting.
Architecture of the WAP Protocol Stack
The following diagram illustrates the general architecture of the WAP protocol stack:
|
Application Layer (WAE) |
|
Session Layer (WSP) |
|
Transaction Layer (WTP) |
|
Security Layer (WTLS) |
|
Transport Layer (WDP) |
|
Bearers (GSM, CDMA, ) |
The WAP protocol stack has a multi-layered architecture (this is very similar to the seven layers model of OSI.
The WAP stack consists of the following layers:
WAE WIRELESS APPLICATION ENVIRONMENT
The Wireless Application Environment (WAE) defines the following functions:
Wireless Markup Language (WML).
WML is an XML-based markup language for the visual display of WAP-based contents. Once HTML and WML will converge into XML, many compatibility problems, during conversion from HTML to WML, will cease to exist.
WML Script.
A script language, very similar to JavaScript.
Wireless Telephony Application (WTA, WTAI).
Telephony services and Programming interfaces.
Content formats.
These are specifications for data formats, including images, telephone directories, calendar information, and so on.
The WAE corresponds to the application layer in the OSI model.
WSP WIRELESS SESSION PROTOCOL
The Wireless Session Protocol (WSP) implements an interface for connection-oriented and connectionless session services. The connection-oriented session service operates using the protocol of the transaction layer. However, the connectionless session service uses a secure or non-secure datagram service.
WSP offers the following basic functions:
- Functions and semantics of HTTP/1.1, using a compact coding scheme
- Pausing and resuming sessions
- A general facility for reliable and unreliable data push
- Negotiation of protocol functions
WTP WIRELESS TRANSACTION PROTOCOL
The Wireless Transaction Protocol (WTP) is a transaction-oriented protocol, executed using a datagram service. WTP offers the following functions:
Three classes of transaction services
(a) Unreliable one-way requests
(b) Reliable one-way requests
(c) Reliable two-way request/response transactions
Optional user-to-user reliability feature.
The WTP user triggers confirmation for each received message.
Optional out-of-band data for confirmations.
Protocol Data Unit (PDU) chaining and delayed confirmation.
In order to reduce the number of sent messages
Asynchronous transactions
WTLS WIRELESS TRANSACTION LAYER SECURITY
The WTLS layer implements a security protocol based on the TLS (Transport Layer Security) industry standard. WTLS is intended for use with the WAP transport protocols and has the following features:
Data integrity WTLS ensures that the data sent between the terminal and an application server is in no way altered or damaged.
Confidentiality WTLS ensures that the data sent between the terminal and an application server remains confidential and cannot be understood by any other participant who may have intercepted the data stream.
Authentication WTLS ensures the authenticity of the terminal and of the application server.
Denial-of-service protection Wireless Transaction Layer Security (WTLS) contains features that will recognize and reject data that has been repeated or not verified successfully. WTLS hinders many typical denial-of-service attacks and protects the upper protocol layers. Though, this is not a perfect solution.
WDP WIRELESS DATAGRAM PROTOCOL
The WDP layer operates on various bearers that depend on the used network
type. WDP offers a consistent interface for the upper layers, so that
communications occurs transparently using one of the available bearer services.
Therefore, the transport layer is adapted to the specific functions of the
underlying bearer.
BEARER
The bearers that are used by the WAP protocol stack form the lower interface of the datagram service and allow the WAP to be used for various network types with specific bearer functions. Thus, WDP is defined for a variety of bearers. For an IP bearer, the transport protocol (WDP) is implemented by User Datagram Protocol (UDP).
WCMP WIRELESS CONTROL MESSAGE PROTOCOL
The Wireless Control Message Protocol defines the error reporting mechanism for WDP datagrams as well as the protocol elements that can be used for diagnosis and informational purposes (for example, WCMP echo request and response). WCMP is determined depending on the bearer used. In IP-based networks, WCMP functions are implemented using the Internet Control Message Protocol (ICMP).
Components of a WAP service
Here we will describe the typical components for the setup of a WAP service.
The following figure shows how the components in a WAP service interact.
WAP terminals
Users of WAP services access WAP content with a WAP terminal.
The following devices can serve as WAP terminals:
Mobile phones with built-in GSM modem, WAP stack, and microbrowser (e.g. Nokia)
Palmtops with GSM phone connected and additional WAP/ browser software
Depending on the features of the device used and the capabilities of its display, there are different quality degrees with WAP services. However, the following features are common to all terminals:
Access to pull services, or browsing, using GSM Circuit Switched Data (CSD), usually at 9600 bps, Point to Point Protocol (PPP) via the V.110 protocol.
Configurable access profile (PPP authentication parameters, access number of access server, Gateway IP address, homepage, etc...)
Optional support of push services using connectionless bearers (for example the Short Message Service)
Access to/ from network carrier
Access to the WAP Gateway in Circuit Switched Data (CSD) connections is enabled through Integrated Services Digital Network (ISDN) bearer channels, packed in E1 PRI connections with 30 channels in each connection. The number of available bearer channels determines the number of WAP terminals that can actively access the WAP Gateway simultaneously.
Network operators should map the dial-in number for the ISDN channel package to a network-internal abbreviated number in order to offer exclusive content to customers and operating billing mechanisms to the content provider. This also allows operators to offer a cost-effective minute-based rate for WAP online time. If different access numbers are used (for example, in order to realize network-independent access), users are encouraged to use "Friends & Family" or "Home City" access numbers.
The MSISDN (Mobile Station identifier- the telephone number) of the WAP
terminal must always be sent using the ISDN channel in order to personalize the WAP services and to generate additional, content-dependent billing information.
Airtime Billing
Billing of the base connection time (base rate for WAP online time) must always be performed by the network carrier.
Access Server
The access server is the PPP termination point for the WAP terminal. One of its responsibilities is allocating dynamic IP addresses to the active WAP terminals.
The access server ensures correct routing of WAP packets from and to the WAP Gateway and performs firewall duties.
By cooperating with the access server and the RADIUS server (enables authentication methods), the WAP Gateway can call up the MSISDN of a WAP terminal in an open session in order to perform personalization and authentication functions. The access server offers RADIUS support for the implementation of authentication mechanisms.
WAP Gateway
The WAP Gateway is at the core of the WAP service. It implements the WAP
stack (WDP, WTLS, WTP, WSP), the necessary content encoders, and a variety of management functions.
By cooperating with the WAP/ HTTP proxy and using the authentication
information originating from the access server, time or event-based billing can be implemented on the Gateway side, in addition to airtime billing.
WAP/ HTTP proxy
The WAP/ HTTP proxy is the interface to the services that actually provide the
requested WAP content. These services (WAP Originating Services) can either be requested via the public Internet, or they can be installed on the content host.
Using a built-in cache mechanism, the proxy optimizes access to external
services and ensures fast access times.
Content Host
The content host is a dedicated HTTP server that is connected to the WAP proxy server via a LAN or WAN and facilitates fast access to (partially) exclusive WAP services. External content providers can install and administrate WAP services on the content host using standard protocols, such as File Transfer Protocol (FTP).
A number of tools for the automatic conversion of ASCII or HTML to the Wireless Markup Language (WML) are available:
Network-internal WAP applications:
In addition to external WAP services (on the content host or on the public
Internet), network-internal WAP applications can be implemented. These
applications are accessed by the WAP Gateway using a dedicated secure
connection.
Detailed billing
Cost control
Management of voice mailbox
Rates information
Configuration module Over-The-Air (OTA) Server
For automatic configuration of the access parameters in the WAP terminal, a
configuration module is available that transmits the set of parameters to the
WAP terminal using the air interface.
The configuration module is also responsible for the setup of a personalized
WAP portal. The subscriber can perform all configuration steps using an
Internet interface.
Authentication module
The authentication module transmits the connection information and relations
provided by the access server to the management units for personalization
and content billing purposes.
Content billing module
The content billing module enables time- or event-based billing, depending on
the requested content. This requires the following things:
The content provider has a corresponding agreement with the network carrier and/ or the operator of the WAP Gateway to market the content.
The content pages (billable) contain the corresponding billing information (in-band signaling).
The
authentication module delivers the phone number of the WAP user who
has requested the chargeable page. A
preliminary page can be displayed to notify users of chargeable
content.
WAP
Development Issues
Following
are several issues that are related to WAP development which are not
standardized yet and the WAP developers should be aware of.
Push
Not Supported - The WAP Wireless
Session Layer (WSP) specification defines the WSP push operation and a
WSP push PDU (Protocol Data Unit). A push operation is not specified for
the HTTP protocol, used by the WAP Gateway server to communicate with
content hosts. To support pushes, the server has to provide an
application interface to allow server based applications to generate a
push to a mobile client. The support of pushes on the client side
depends on the capabilities of the handsets to handle pushed content.
The Nokia over-the-air (OTA) configuration proposal to the WAP Forum
describes the use of a connectionless push over the SMS bearer, to
transfer the configuration data to the handset.
Lack
Of Cookies for Session Management - There are no "cookies" for
session management, i.e. to hold the session together. Cookies are used
on the fixed Internet to identify the web browser and thereby assist in
providing customized and streamlined services. Instead, some WAP
applications use indexes in the URL as an alternative. The cookie
information is transmitted via HTTP headers. Because WAP Wireless
Session Layer (WSP) is based on HTTP headers, it should be possible to
transmit cookie information to the clients. The problem may be the
clients themselves, which may currently not support the handling of
cookie HTTP header information or the ability to save this information
to a persistent storage in the mobile phone. Some third parties have now
announced support for cookies.
Fear
of Viruses being transnmitted via WAP -
The mobile phone will follow a similar development path to PCs- with
good ideas like screensavers and bad ideas like computer viruses
appearing on mobile phones such as they do on PCs today. Solutions are
being developed by various private companies.
Premature
Encryption Endpoint - The
Wireless Transport Layer Security (WSLS) defines encryption between the
Mobile Station and the WAP Gateway. The "endpoint" of the
encrypted WTLS data is the WAP Gateway proxy server. To have a secure
connection to a content host (e.g. banking server) the Gateway proxy
server has to establish secure (https) connections to this hosts. In
this case the proxy server has access to the decrypted data received via
WTLS from the mobile station or from the content host via https.
Small
Downlable Unit Size - WAP
incorporates no compression techniques for the textual content, although
the WML markup commands are compressed. Additionally, the
"deck"- the smallest unit of downloadable information in
Wireless Markup Language- is limited to a maximum of 1400 bytes. This
means that applications need to be specifically designed to be very code
efficient by using templates and variables and keeping information on
the server and using the cache on the phone. WML byte code converting (WMLC)
defines a (maybe inefficient) compression technique by string tables.
With this technique duplicate strings in the WMLC bytecode are avoided.
This reduces the size of the data to transfer to the mobile client. The
WSP SDU size of 1400 bytes is a default value. An increased size may be
negotiated by a mobile client within the WSP capabilities. The WAP
transport layer (WTP) is able to handle greater SDU sizes than 1400 too,
by using SAR (Segmentation and Re-assembly).
Applications
for WAP
The
Wireless Application Protocol (WAP) is being used to develop enhanced
forms of existing applications and new versions of todays
applications.
The
WAP will allow customers to easily reply to incoming information on the
phone by allowing new menus to access mobile services.
Early
applications are modification of existing applications such as
information, along with applications such as mobile commerce, mobile
banking and mobile games.
Mobile
Commerce
There
are several issues relating to the development of mobile commerce
applications, such as security, integration with the retail and banking
hardware and systems, non-standardized mobile infrastructure and
competing e-commerce standards. Additionally, there is a lack of
standards relating to the mobile phone to network interface, the
interfaces between host and mobile platforms and between different
mobile platforms. As such, the scalability of mobile commerce is
questionable.
There
are also questions about the appropriateness of using a mobile phone as
the interface to e-commerce applications. The MMI (Man Machine
Interface) on mobile phones is currently sub-optimal and difficult for
mass-market users to manipulate.
However,
this area of electronic commerce applications is expected to contribute
to grow significantly in the future, as mobile phone penetration
delivers a critical mass of potential customers for such services.
It
is expected that the mobile commerce will become just an extension of
electronic commerce on the Internet. There will not need to be any
special applications developed for the mobile to take into account
screen, bandwidth and security limitations of the mobile device.
The
value chain for mobile commerce took a step further in April 2000 with
the announcement that Motorola, Ericsson and Nokia had partnered to see
mobile commerce standards. The possibility to handle trusted electronic
transactions from a personal mobile device is regarded as one of the
most important areas of the mobile Internet. As such, the aim of these
companies is to offer solutions where security and payment services will
be integrated as a standard into the mobile devices in years to come.
Some of the key technology cornerstones will be WAP security functions,
such as WTLS (Wireless Transport Layer Security), WIM (Wireless
Identification Module), wireless public key technologies and others.
Mobile
Banking
The
successful implementation of mobile banking programs incorporates
several different elements such as private information services, WAP and
security.
There
are a few technology limits affecting how the mobile banking service is
designed:
Any
information that is useful to bank customers can be provided such as
last 4 transactions, account balances, overdraft limits and so on.
Information
can be provided in a number of different ways. It can be pull based and
requested on an adhoc basis via a telephone call to an electronic voice
menu to initiate the information. Alternatively, the user could send an
information request in and get an information message back, or the
service can be push based such that information is automatically
generated at set intervals or on the basis of events.
The
mobile banking service can run on all existing mobile phones or to be
tailored for a particular branded phone or protocol-compliant phone,
e.g. WAP.
Protocols
such as WAP allow not just information provision, but also secure mobile
transactions and electronic commerce.
Mobile
banking suppliers using WAP include Materna (www.materna.com).
Banks offering services over WAP include Deutsche Bank and Visa
International.
Banking
services using WAP from around the world include:
In
the UK, Woolwich company offered 100 of its customers interactive
banking over a WAP enabled mobile phone. Using a Nokia 7110 handset,
customers will be able to view balances and transactions, pay bills, and
transfer money on current, savings and borrowing accounts.
In
Belgium, CCB (the Belgian bank) officially launched its mobile banking
venture. This will allow customers to check balances, carry out payments
and transfers, and - in the future - buy shares from a WAP mobile phone.
Games
Mobile
games suppliers using WAP include:
www.digitalbridges.com
, http://www.wapholesun.com,
www.k-mobile.com
and others.
Ringtones
Unified
Messaging
Unified
messaging is an emerging value-added network service that is
particularly compelling because it elevates communication above the
technology used to communicate the message takes precedence over the
media. Currently, it is difficult to manage all the different kinds of
messages that people get -
they have to dial in and pick up emails, pick up their faxes from a fax
machine, call in and listen to voice mail, and so on. Unified messaging
involves providing a single interface for people to access the various
kinds of messaging they use. Be the messages of any kind, they can be
conveniently accessed from a single point in the most actionable form.
The
user typically receives a short message notifying them that they have a
new message in their unified messaging box. The short message often
includes an indication of the type of the new message. With WAP, users
have a menu on the phone from which they can access and mange their
unified messaging box.
Internet
Email
The
Internet email alert is provided in the form of a short message that
details the sender, the subject field and first few words of the email
message. Most of the mobile Internet email solutions incorporate
filtering, such that users are only notified of certain messages with
user-defined keywords in the subject field, or from certain senders.
Because
of the high and increasing usage of Internet email to communicate
globally, and the benefit from using WAP Push to notify mobile users
about important new email messages, this is likely to be a fast growing
and popular application for WAP.
Affinity
Programs
Some
examples of partners between companies in different areas of the mobile
value chain to develop WAP services include:
Hong
Kong network operator Hutchison Telecom has joined with Health Care
International Holdings to launch an online medical service portal,
Healthcare2U.com. Subscribers to Hutchisons network can access the
medical portal via WAP phones.
Finnair
will enable passengers to make, alter and cancel reservations using WAP-enabled
mobile phones. The service operates in English, but currently is only
available to customers with Finnish phone service providers.
Ericsson
announced a deal to make the guide Michelin travel publications
available on WAP mobile telephones. The new service will give the
customers instant access to a database of some 60,000 hotels and
restaurants across Europe via WAP.
Customer
Service
By
providing mobile phone customers with information about their account,
the WAP can help to avoid the need for expensive person to person voice
calls to customer service centers.
Customer
service suppliers using WAP include Phone.com (www.phone.com)
and Categoric (www.categoric.com).
Categoric specializes in event alerts. Every time an event of
interest to the customer happens, SMS or WAP are used to let them know.
Positioning
The
SMS is ideal for sending GPS information such as longitude, latitude,
bearing and altitude. GPS information is typically about 60-character
length, leaving room for other vehicle-specific information.
Vehicle
Positioning suppliers using WAP include www.wapolution.com.
Instant
Messaging
Instant
messaging is a cross between chat and email that allows people to view a
listing of people they frequently communicate with, determine if these
people are currently available for communication (i.e. online), and send
and receive messages instantaneously. The tendency is to send instant
messages to people rather than emails if you find that they are online.
Instant
messaging was launched in early 1997 and continues to grow in popularity
with over 100 million total users.
Wireless
Instant Messaging is another example of the extension of the same
services that people can access on the Internet becoming increasingly
available on mobile phones. This is initially done through gateways that
perform protocol conversion and reduce the size of the communication
down to that which can be handled by low bandwidth wireless services.
Over time, the gateways will not be needed, as seamless access to
unmodified services becomes more widespread.
Instant
Messaging suppliers using WAP include AOL Tegich (www.tegic.com).
Chat
Because
of its association with the Internet, the General Packet Radio Service (GPRS)
would allow mobile users to participate fully in existing Internet chat
groups rather than setting up their own groups that are dedicated to
mobile users.
Qualitative
Information
The
length of a short message of 160 characters suffices for delivering
information when it is quantitative such as a share price or a sports
score or temperature. However, when the information is of qualitative
nature, such as a horoscope or news story, this 160-character length is
too short. Therefore, GPRS will likely be used for qualitative
information services, but SMS will continue to be used for delivering
most quantitative information services.
Information
services suppliers using WAP include Infospace.com, I3 Mobile and
others.
Future
Prospects
WAP
introduces several new concepts of the use of cellular phones, and new
services that costumers can get. In a couple of years the 3rd generation
of the cellular protocols will start to appear with high capabilities of
data transferring and will give another boost to WAP. Further more
WAP has many advantages that handle the very problematic bearer of the
wireless phone, but we should not forget WAPs disadvantages such as
some inefficacy and high cost of the services to the end user. Some of
theses disadvantages will be overcome when the WAP will be used and
installed in many handsets.
WAP
is an important development in the high-tech industry, network operators
are aggressively trying to speed up penetration of WAP phones around the
glob, but WAP has still a way to go, there are several issues that need
to be handled, and there is still some time till the Wireless
Application Protocol will be widely used in hand-sets. Time will show if
WAP is capable to become the widespread customer used protocol.
Glossary:
WAP - Wireless Application Protocol
MMI
- Man-Machine Interface
WAE
- Wireless Application Environment
WDP
- Wireless Datagram Protocol
WML
- Wireless Markup Language
WSP
- Wireless Session Protocol
WTA
- Wireless Telephony Application
WTLS
- Wireless Transport Layer Security
WTP
- Wireless Transaction Protocol
CSD Circuit Switched Data
GPRS General Packet Radio Service
GSM Global System for Mobile Communication
HTML HyperText Markup Language
HTTP HyperText Transfer Protocol [RFC2068]
IMAP4 Internet Message Access Protocol Version 4
IVR Interactive Voice Response
LAN Local Area Network
MSISDN Mobile Station ISDN number
OTA Over-The-Air (Configuration)
POP3 Post Office Protocol Version 3
PPP Point-to-Point Protocol
RADIUS Remote Dial-In User Service
RFC Request For Comments
SMS Short Message Service
URI Uniform Resource Identifier
URL Uniform Resource Locator
W3C World Wide Web Consortium
WAN Wide Area Network
WBMP Wireless BitMaP
WCMP Wireless Control Message Protocol
WTAI Wireless Telephony Application Interface
