Transcript Wireless Application Protocols (WAP)

WAP and wireless WWW
Christopher Hoffman
Anuradha Rangineni
Changju Lee
Contents
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Introduction
WAP Objectives
WAP Programming Model
WAP Protocol Stacks
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WAE (Wireless Application Environment)
WSP (Wireless Session Protocol)
WTP (Wireless Transaction Protocol)
WTLS (Wireless Transaction Layer Security)
WDP (Wireless Datagram Protocol)
Wireless WWW
Introduction
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Wireless Application Protocol
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Standard for wireless application to provide data and voice
services to wireless handheld devices
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WAP application is enable to access WAP sites using WAP browser
(Micro-browser)
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WAP sites (Mobile internet sites) are websites written in, or
dynamically converted to, WML
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XHTML MP(Mobile Profile) is defined as a standard WML in
WAP 2.0
Examples of WAP application
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Email by mobile phone
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Tracking of stock market prices
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Sports results
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News headlines
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Music downloads
Objectives of WAP
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Supporting the standard Internet protocols
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Interoperability among service providers
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Overcoming shortfalls of the wireless medium
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Overcoming drawbacks of handheld devices
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Increasing efficiency and reliability
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Providing security, scalibility and extensibility
WAP Programming Model
WAP Optional Proxy Model
WML Content
HTML Content
Filter
WAP protocol stack
WAP protocol stack
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Scalable environment for application
development
Well defined interfaces to other services
WAP protocol stack
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Wireless Application Environment (WAE)
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Provides model for accessing WWW URLs
Uses uniform resource identifiers (URIs)
Uses WML standard markup language, an
efficient binary encoded form of HTML
Provides a scripting language analogous to
JavaScript
Provides a set of telephony applications
WAP protocol stack
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Wireless Session Protocol (WSP)
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Push mechanism reduces number of requests
made by client
Push to all registered clients useful in multicast
or broadcast applications
Binary equvalent to HTTP
Sessions can be suspended and reestablished
to save power and avoid overhead
WAP protocol stack
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Wireless Transaction Protocol (WTP)
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Lightweight version of TCP
Low overhead: no setup or teardown
3 classes of service:
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Class 0: unreliable send with no ACK
Class 1: reliable push
Class 2: classical request-data-ACK cycle
WAP protocol stack
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Wireless Transport Layer Security (WTLS)
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Security between WAP client and WAP server
Features: datagram support, optimized
handshake, dynamic key refeshing
Goals: data integrity, privacy, authentication,
and DoS protection
WAP protocol stack
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Wireless Datagram Protocol (WDP)
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Defines transport layer
Contains bearer-specific layer that optimizes
data transfer to SMS, USSD, CSD, or CDMA
Wireless control message protocol (WCMP) is
responsible for error-handling
WAP 2.0 and i-mode
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i-mode
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Packet switched network built on circuit switched
mobile phone network
Billed by the packet
Uses cHTML (compact HTML)
WAP 2.0
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Packet switched
Interoperable with WAP 1.0
Billed by connection time
Pull and Push models
Optimizing Web Over Wireless
Limitations of wireless networks
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Low bandwidth
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Low reliability
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High latency
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High cost per byte transferred
Drawbacks of HTTP
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High connection overhead- a new TCP socket is opened for
every new HTML object
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Redundant capabilities transmission - information regarding
browser capabilities is included in every HTTP request
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Verbosity – HTTP is ASCII encoded
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WebExpress suggests an Intercept model to be applied
In this model two entities are introduced
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CSI – client side interface
- resides with the browser on the device
- communication takes place through the loopback feature of TCP/IP
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SSI- server side interface
-resides at network gateway or FA in MobileIP
-communicates with server over wired network
Intercept model
lindquist
Optimizations
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Caching
- objects are purged after sessions or may persist between them
- persisting objects increase cache hit ratios
- appropriate cache coherency methods are added
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Differencing
- different replies to same application server are often different but tend to be
similar
- base object carries fundamental features which do not change across
transactions
- only difference stream computed by server is transmitted for any new
transaction
Optimizations
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Protocol reduction
- aims at reducing overhead of repeated set up and tear down of TCP/IP
connections
- a single TCP/IP connection is established between CSI and SSI for entire
session
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Header reduction
-HTTP requests have prefixes like capabilities of browser and various content
formats handled by it
- instead, CSI sends this information in first request and SSI records this
information
-for all other requests sent by CSI, SSI automatically inserts this capability into
each packet meant for origin server