Transition to

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					The Mobile Internet

    Nour El Kadri
 University Of Ottawa
                  Mobile Internet

TCP/IP was designed to isolate developers from the
idiosyncrasies of the different standards
We need something to do the same for the mobile world
since the TCP/IP did not cater for wireless links and
mobile devices
Transition standards have been developed to bridge the
gap. EX:
       WAP
Work of 3GPP on Open Service Access (OSA)
3GPP Mobile Execution Environment (MExE) –
Combining WAP with simple Java.
    TCP/IP on Mobile Networks
• Multiplexing at the Physical and Data Link level
   – 2G – Circuit switched connections
   – 2.5G and 3G – Packet switching
• Routing is difficult due to adaptation difficulties in
  TCP/IP to the demands of mobile
  communications
• Mobile IP is a variation of IP at the network layer
  that caters for some of these difficulties
• Mobile IP is an integral part of 3G, but GPRS
  and CDMA2000 1X support simplified versions
  of mobile IP
   Mobile IP – Routing Packets to
           Mobile Nodes
• Packets contain headers that identify Destination
  Addresses
• IP addresses are organized where addresses in
  the same network have identical prefixes
• As soon as a node or mobile Device like a PDA
  start moving between networks of different
  prefixes…..Things start to break down
• Regular IP offers two solutions for dealing with
  this. Neither is feasible in a mobile environment
  – Update all routing tables with node-specific entries
  – Assign new IP addresses to the mobile node
      The Remedy – Mobile IP
• It does not require any changes to software or
  hardware for the existing installed base of IPv4
  and routers except those involved in mobility
  services.
• This is done using:
  – Tunneling
  – Care-of-address
• Home agents and mobile agents take care of
  encapsulating messages and sending them to
  their intended receipients
  TCP: The Wireless Link Requires
        Special Treatment
• IP is a best-effort service…No guarantee of delivery
• TCP makes sure that packets are received, reassembled
  and delivered to the application needing them
• TCP also addresses flow and congestion control
   – In wireline, missing acknowledgement is mostly due to
     congestion
   – In mobile wireless, missing acknowledgement is rarely due to
     congestion, it is mostly connection drops and transmission errors
• Differentiation between the wireless link and the rest of
  the network is a partial solution.
• GPRS adopts a re-transmission scheme as a solution
• Sender and receiver agreements are a problem in
  wireless due to intolerable delays
         The Mobile Internet: Early
               Precursors
• Other challenges include developing
  presentation languages that accommodate:
     •   The limited screen size
     •   Memory
     •   Power of mobile devices
     •   Limitations of mobile networks
• Even HTTP is not suited for wireless due to its
  stateless nature
Solutions have been devised:
  – AT&T PocketNet
  – Palm.Net-WebClipping
  – NTT DoCoMo i-Mode
                AT&T PocketNet
• Introduced in 1996 by AT&T Wireless
• It relies on CDPD which includes a basic TCP/IP
  protocol stack
• It uses HDML instead of HTML and a special
  microbrowser (UP.View) developed by unwired planet,
  later renamed as Phone.com (acquired by OpenWave)
• HDML introduced the Deck of Cards Metaphor
   – Devices has tiny screens
   – Many user applications can be devided into small sets of
     interaction (cards)
   – Send all associated screens (cards) all at once to a mobile
     device
   – HDML evolved into the Wireless Markup Language the
     presentation language of WAP
         Palm.Net - WebClipping
• A web service introduced by Palm in 1998 for its PDAs
• Uses a solution called WebClipping
• Webclipping stores the static part of web pages on the
  PDA allowing only the dynamic part to be sent over the
  wireless link
• Several hundred web services have been adapted to run
  on Palm.Net covering:
   –   Finance
   –   Enterprise applications
   –   Shopping
   –   Information
   –   Entertainment service
            NTT DoCoMo i-Mode
• Operates on top of PDC-P packet switched network (known as
  DoPa) which has a built-in TCP/IP stack
• It relies on cHTML for content presentation designed by Access
  Corporation
• DoCoMo’s i-Mode servers take care of Authentication and billing for
  official content providers
• i-Mode vs. WAP competition?
• Recent move from cHTML to XHTML Basic which is adopted by
  WAP (known as WAP2.0) for replacement of WML
• i-Mode started supporting Java based applications through its i-appli
  service which relies on Sun’s J2ME providing:
    – End-to-end security
    – More interactive applications like games, zoomable maps
    – Regular traffic updates and similar services
   Wireless Application Protocol
• WAP Forum founded in 1997 by Phone.com, Ericsson, Nokia and
  Motorola
• Open standard that is device and bearer-independent
• Due t its wide adoption, it achieved the badly needed economies of
  scale
• Often criticized as too far a deviation from W3C and IETF standards
• Developers find it has presentation constraints and question its
  security approach
• Its limitations are being addressed with time, for instance, WAP 2.0
  has support for:
    –   End-to-end security
    –   Color graphics
    –   Animation
    –   Push technology
• WAP collaboration with W3C and IETF led to adoption of XHTML
  Basic (WML2) and support for TCP and HTTP
          WAP Architecture
• WAP is not a Protocol, but a suite of
  protocols
• It bridges the gap between mobile bearer
  services and basic Internet Protocols such
  as:
  – TCP/IP
  – HTTP
• This was done through gateways in the
  early stages
      WAP Gateway and Legacy
          Protocol Stack
• WAP gateway or proxy was used to interface
  between WAP protocol Stack and the regular
  internet protocol stack
• WAP content is encoded into a compact binary
  format before transmission
• WAP gateway decodes it into text interpreted by
  HTTP and vice versa
• WAP gateway helps improve communication
  efficiency, authenticates users, provides support
  for additional billing functionality
Operating without a WAP Gateway
• 2.5G and 3G have a protocol stack that supports the IP
  protocol. (WAP 2.0, W3C, IETF)
• It is a variation of the TCP and HTTP protocols profiled
  for operation over a wireless link
• Wireless HTTP provides:
   – Compression of content
   – Secure tunneling between Mobile device and web server
   – In theory, that should eliminate the gateway
• In practice, a gateway is still needed to provide other
  services like:
   –   Billing
   –   Location-based services
   –   Privacy features
   –   WAP gateway is needed for push services
WAP Legacy Protocol Stacks
Before 2.5G and 3G, we needed the
gateway and the legacy of protocol stacks
which included:
– Wireless Datagram Protocol
– Wireless Transport Layer Security
– Wireless Transaction Protocol
– Wireless Session Protocol
– Wireless Application Environment
Wireless Datagram Protocol (WDP)
• Lower level protocol
• Sits between bearer services and upper level
  protocols in the stack
• Depending on the bearer service, its
  functionality changes
• In cases of built-in IP bearers like GPRS and
  UMTS, its functionality is reduced to that of UDP
• It simply insures that packets are delivered to
  upper layers
 Wireless Transport Layer Security
• Designed to provide Privacy, Data Integrity and
  Authentication between two communicating applications
• It is based on the TLS protocol commonly used over
  fixed Internet (formerly known SSL)
• TLS operates on top of TCP, thus WTLS has to take on
  some of that functionality
• Designed to operate over low-bandwidth and high-
  latency connections
• Security is a burden, so developers have to choose the
  level of security needed in a cautious way.
• The Gateway poses a security gap.
  Wireless Transaction Protocol
• Light-weight transaction-oriented protocol – mostly for
  thin clients with little memory and power
• Acts as a substitute for TCP while handling some of
  HTTP functionality
• WTP supports three classes of transaction services

   – WTP Class 0: for unreliable message transfer
   – WTP Class 1: for reliable message delivery without a result
     message
   – WTP Class 2: for reliable message delivery with a result
     message confirming reception – useful for banking applications
     as it allows transaction rollbacks
    Wireless Session Protocol
• Provides HTTP/1.1 functionality. It allows for
  sharing of state between client and server to
  optimize content transfer
• It allows for Capability Negotiation: level of
  protocol functionality during a session
• You can resume suspended sessions from
  where you left
• It allows the management of multiple sessions.
  EX: from a GPRS session to read e-mail to a
  UMTS session to join a videoconference.
 Wireless Application Environment
• Most visible part of WAP to both users and
  developers
• It includes
  – WAP microbrowser
  – WAP markup and scripting languages
• Important part of WAE is the Wireless
  Telephony Applications Interface (WTAI).
  It allows users to access telephony
  applications from WAP sessions
     WAP Protocol Stack for Fast
       Bearers with Built-in IP
• Wireless Profiled TCP - version of TCP
  optimized for wireless Environments
• Wireless Profiled TLS – a wireless profile for the
  TLS protocol found on the wired Internet
• Wireless Profiled HTTP – fully interoperable
  version of HTTP/1.1 allowing for message body
  compression and secure tunnels
• Wireless Application Environment – next slide
The Wireless Application Environment

It is the part of WAP that users see. It
consists of:
 – WAP markup and scripting languages
 – WAP microbrowser
 – Wireless Telephony Applications Interface
      WAP Markup and Scripting
           Languages
• WML referred to as WML1 or WML1.x
• WMLScript is the scripting language
• With WAP2.0 we have XHTML Basic which is a subset
  of XHTML recommended by W3C
• Deck of cards metaphor
• WAP allows for Client-Side logic using its WMLScript
  which is a bare-bones version of JavaScript. Thus, some
  processing is done at the client side
• Code reusability is possible due to the import of some
  code that is written for PCs that can be used for WAP.
  Thanks to W3C.
          WAP Microbrowser
• Sits on the client with a role of interpreting and
  presenting content
• Content can be written with: legacy WML
  language, WML Script or XHTML Basic
• Some companies have their own microbrowsers
  like Ericsson and Nokia
Other Third party microbrowsers available:
   – Open Wave’s Mobile Browser
   – AU-System’s browser for PalmOS, Windows CE and
     EPOC platforms
   – Microsoft’s Mobile Explorer
   – 4thPass KBrowser, runs Sun’s Java KVM
 Wireless Telephony Applications Interface

• Contains a list of APIs to invoke
  applications from WAP browser
  – Accepting restaurant Ads,
  – Reservations
  – Saving telephone numbers to address book
  All without having to quit a WAP browser
       The WAP Usability Saga
• Deck of Cards Metaphor
• Introduction of Persistent Sessions in WSP
• Use of WAP User Agent Profiles to better tailor
  content
• Integration of WAP with telephony applications
In spite of this there are complaints:
  –   Slow connections
  –   Dead ends or sites being down
  –   Sites with poor signposting
  –   Uneven content quality
  –   Small screens
Evolving Application Architectures-
How Open is the Mobile Internet?
•   Anyone can set up an Internet shop
•   Click-through economy
•   3GPP’s Open Service Architecture
•   Service Enablers
•   Personal Service Environment
            Java and MExE
• Device Independence from bearer
  services – write once run everywhere
• J2ME comes in two different flavors
  – A connected device configuration
  – A connected limited device configuration

				
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