Transcript The Wireless Application Protocol

 WAP
 A standard for delivery of information, data and services
to both enterprise and consumer users over wireless
networks.
 Consists of components
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Network transport protocols
Security capabilities
An application environment – browser ML, scripting and
telephony
 A modular architecture – which allows
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Variety of physical implementations
Deployment configurations
Integration points with existing web and information services
Origins of WAP
 Many successes with No Success
 Companies designed technologies to deliver wireless data to mobile but none
were able to form a standard.
 Analog Modem Technologies
 Supports analog data communications – 4800 to 9600 bps – effective
throughput varies based on signal strength and quality
 Eg. Enhanced Throughput Cellular (ETC) Technology
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Developed by AT & T Paradyne , 1994
ETC equipped Cellular modems operate on the physical and link layer protocols.
Reduces signal transmission by 6 dB – to improve reliability of data transmission over a
wireless connection that is optimized for voice traffic.
Monitors network and dynamically adjusts the transmission speed every five seconds
Transmits small, 32-byte chunks to reduce retransmission time and improve
throughput
 Similar techs: EC2 (Enhanced Control Cellular) – Motorola, Enhanced Cellular -
Microcom
Origins of WAP – contd…
 Wireless Middleware Solutions
Extend the transport protocols to improve throughput, reliability or
user experience.
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Secureway Wireless Gateway (Artour) – IBM
 Software in client and server transparently manage the use of
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air link beneath any standard TCP/IP application.
Compressing the data
encrypting the packets
shutting down the cellular link during inactivity
Fast reconnection
Delayed acknowledgements
Application middleware: provides caching and data reduction
capabilities
 ExpressQ – NetTech Systems (now BroadBeam)
 Provides asynchronous messaging
 Push
 Encryption
 Roaming capabilities on a variety of network and devices
 Includes a developer’s kit for building applications
 Handheld Device Markup Language (HDML) and Handheld
Device Transport Protocol (HDTP) – Unwired Planet (now
Phone.com) – It includes:
 A micro-browser
 Optimized protocol stack for supporting web access from
mobile phones
 Content written in HDML and sent to gateway for encoding
and then transmitted
 AirMobile – Motorola
 Provides optimized access to Lotus Notes and cc:Mail
over wireless networks
 Narrowband Sockets (NBS) - Nokia and Intel
 Provides optimized data transport services for UDP over
circuit-switched data and GSM SMS
 Supports both delivery of notifications and pushed
contents
 Now part of Nokia Smart Messaging Platform
Each of these middlewares have achieved some success
within particular markets and industries, but none of
them were mass deployed for Mobile Internet
Data-Optimized Networks
 Wireless networks that support wireless data
 CDPD
 Cellular Digital Packet Data
 Transmits in idle space within an analog voice network.
 Effective data throughputs 9.6 to 14.4 Kbps.
 Network latency approx. 1 sec
 Coverage – throughout United States and Canada
 ARDIS
 Motorola and IBM
 Packet network
 Throughput approx. 2.4 Kbps
 Network latency 4 to 10 seconds
 Coverage – major US metropolitan markets
 RAM Mobile Data
 RAM and BellSouth
 Packet network
 Effective data throughputs approx 4 Kbps.
 Network latency 4 to 8 secs
 The network is used to support Palm.net service offered by Palm Computing
Data-Optimized Networks (DONs)
 Ricochet
 Metricom
 Packet network – uses low power base stations placed atop
light poles
 Throughput upto 128 Kbps
 Network latency 1 sec
 Limited Coverage – in campus or corporate env
 Commonalities in these DONs
 Limited coverage
 Special radios required
 High per-packet costs
 So market penetration limited to specialized vertical
application like public safety industries – not for mass
consumer market
Need for a Mobile Internet Standard
 Why all the above efforts failed?
 Content and application developers reluctant to support
as they didn’t have mass consumer market
 Handset manufacturers reluctant to build device unless
sufficient number of network operators and service
providers were willing to market and distribute those
handsets
 s/w and h/w providers- didn’t find enough sales volume
to recover development costs itself
 n/w and service providers didn’t want to get locked into
a single infrastructure vendor , with not enough set of
services and quality handsets
Need for a Mobile Internet Standard
Need for a Mobile Internet Standard
 Why a single standard needed?
 Content and application developers develop content in a
single format which can be delivered over all networks
and to all phones
 s/w , h/w and tools vendors – develop technologies
which will be useful to a broad set of people
 Handset manufacturers can rationalize their product
line and sell the handsets through network operators
 Network operators would be assured on an open,
competitive market for handsets, infrastructure,
applications and services
Initiation of WAP standard
 AT & T Wireless Services (AWS) sought to develop a wireless
data infrastructure that was supported by multiple handset
manufacturers.
 AWS hosted a meeting in Seattle, Washington – calling people
from Ericsson, Motorola, Nokia and Phone.com.
 They announced a joint effort – WAP on 26th June ’97
 WAP Forum – Board of Directors – Representatives of the 4
companies
“The initiative is aimed at aligning the companies efforts to bring
advanced applications and Internet content to digital mobile
phones. This alignment will result in numerous benefits, among
them providing operators differentiation and new business
opportunities. In addition, developers of applications and content
will be aided, since a single protocol and markup language will
work with any vendor’s compatible handsets”
Initiation of WAP standard
 The 4 companies promised to publish a public
standard by september 97. Other few companies also
joined in two weeks.
 They decided that WAP standard would incorporate 3
existing technologies
 HDML – Phone.com’s – would be the common markup
language
 NBS – Nokia – would become the optimized transport
protocol and HDTP – Phone.com’s would be the
optimized session protocol
 Intelligent Terminal Transfer Protocol (ITTP) – Ericsson
would provide foundation for the telephony application
services
Initiation of WAP standard
 Throughout summer and fall of 97, they tried to
integrate these technologies into a single standard –
very complex
 All the 4 companies didn’t want to develop a standard
which would benefit any one of them at the other’s
expense.
 So, by september 97, they were able to publish only a
WAP architecture document.
Initiation of WAP standard
 Key issues faced during the specification design process
 Should the standard be layered?
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Tightly integrated stack – greater n/w optimization, efficient
implementation, but complex to integrate the core technologies
Layered approach – allows partial implementations of the standard,
can provide APIs at each layer, better segmentation of design
responsibilities
Resolution:
 WAP Forum’s Directors decided, the WAP will be layered, but
implementer can merge layers to provide smaller
implementations
 Adv: allowed for purity and manageability of design, supported
efficient implementations
 Disadv: designers could not define standard interlayer APIs
Initiation of WAP standard
 Should IR-OBEX or HDTP be used as the session
layer?
 The IrDA (Infrared Data Association) – developed a
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session-layer protocol – IrOBEX – binary protocol
Supports both push and pull semantics for accessing
data
HTTP-like semantics for Wireless devices
Met many needs of WAP. But not enough to run over a
wide range of wireless networks
Resolution:
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WAP included an new protocol stack – which borrowed ideas
from both NBS and HDTP but differed significantly from both
Initiation of WAP standard
 How should connection-oriented and connectionless
sessions be supported?
 Fig (next slide) – HDTP rested on optional security layer
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which in turn was on NBS – conflicted with each other.
Redundancy was there – both provided data reliability.
NBS – offered both connctn-oriented and connectnless
abstraction
So security layer was forced to support both
HDTP had to provide 4 configurations
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Secure connection
Insecure connection
Secure datagram
Insecure datagram
Initiation of WAP standard
 Security layer ran on top of a datagram layer – so susceptible to attack from
intruder
 Resolution: Resolved in two stages
 (1) During fall of 97 all the three protocols were redesigned
 HDTP – Wireless Session Protocol (WSP)– similar to HTTP
 Security layer – Wireless Transport Layer Security (WTLS)
 NBS – Wireless Transport Protocol (WTP) - – reliable datagram,
request-response transactions.
 (2) During first quarter of 98, WTLS protocol was moved beneath WTP
– to enable only secure datagrams
 By early 98, first version of WAP standard was nearing completion.