Mobile Computing - PDF by xiangpeng

VIEWS: 15 PAGES: 56

									               Mobile Computing
                     Part II: Mobility Support
                           Prof. Dr.-Ing. Jochen Schiller
                    FU Berlin, Computer Systems & Telematics

                  Mobile IP                              WAP & Co.
                       Motivation                               1.x, 2.0, i-mode
                       Basics                            Execution Environments
                       Problems                                 Java, i-αppli, .NET

Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School    50
             Motivation for Mobile IP

Routing
         based on IP destination address, network prefix (e.g. 129.13.42)
         determines physical subnet
         change of physical subnet implies change of IP address to have a
         topological correct address (standard IP) or needs special entries in the
         routing tables
Specific routes to end-systems?
         change of all routing table entries to forward packets to the right destination
         does not scale with the number of mobile hosts and frequent changes in
         the location, security problems
Changing the IP-address?
         adjust the host IP address depending on the current location
         almost impossible to find a mobile system, DNS updates take to long time
         TCP connections break, security problems




Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   51
             Requirements to Mobile IP (RFC 3220, was: 2002)

Transparency
         mobile end-systems keep their IP address
         continuation of communication after interruption of link possible
         point of connection to the fixed network can be changed
Compatibility
         support of the same layer 2 protocols as IP
         no changes to current end-systems and routers required
         mobile end-systems can communicate with fixed systems
Security
         authentication of all registration messages
Efficiency and scalability
         only little additional messages to the mobile system required (connection
         typically via a low bandwidth radio link)
         world-wide support of a large number of mobile systems in the whole
         Internet


Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   52
             Terminology
     Mobile Node (MN)
               system (node) that can change the point of connection
               to the network without changing its IP address
     Home Agent (HA)
               system in the home network of the MN, typically a router
               registers the location of the MN, tunnels IP datagrams to the COA
     Foreign Agent (FA)
               system in the current foreign network of the MN, typically a router
               forwards the tunneled datagrams to the MN, typically also the
               default router for the MN
     Care-of Address (COA)
               address of the current tunnel end-point for the MN (at FA or MN)
               actual location of the MN from an IP point of view
               can be chosen, e.g., via DHCP
     Correspondent Node (CN)
               communication partner
Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   53
             Example network

                     HA
                                                                                                MN


                     router

    home network                                                                     mobile end-system
                                        Internet
(physical home network
for the MN)
                                                                                FA foreign
                                                                                     network
                                                                       router
                                                                            (current physical network
                                                                            for the MN)
      CN

            end-system                        router

Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School       54
             Data transfer to the mobile system

                     HA
                               2
                                                                                               MN



    home network                                                      3                receiver
                                        Internet

                                                                               FA    foreign
                                                                                     network


                                                         1. Sender sends to the IP address of MN,
                                                            HA intercepts packet (proxy ARP)
                        1                                2. HA tunnels packet to COA, here FA,
      CN
                                                            by encapsulation
                                                         3. FA forwards the packet
            sender                                          to the MN

Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School     55
             Data transfer from the mobile system

                     HA
                                                                                       1       MN



    home network                                                                       sender
                                        Internet

                                                                               FA    foreign
                                                                                     network


                                                         1. Sender sends to the IP address
                                                            of the receiver as usual,
      CN
                                                            FA works as default router

            receiver

Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School     56
             Network integration

     Agent Advertisement
              HA and FA periodically send advertisement messages into their
              physical subnets
              MN listens to these messages and detects, if it is in the home or a
              foreign network (standard case for home network)
              MN reads a COA from the FA advertisement messages
     Registration (always limited lifetime!)
              MN signals COA to the HA via the FA, HA acknowledges via FA to MN
              these actions have to be secured by authentication
     Advertisement
              HA advertises the IP address of the MN (as for fixed systems), i.e.
              standard routing information
              routers adjust their entries, these are stable for a longer time (HA
              responsible for a MN over a longer period of time)
              packets to the MN are sent to the HA,
              independent of changes in COA/FA
Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   57
             Encapsulation




                                        original IP header       original data


                    new IP header                       new data


                     outer header          inner header          original data




Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   58
             Encapsulation

Encapsulation of one packet into another as payload
          e.g. IPv6 in IPv4 (6Bone), Multicast in Unicast (Mbone)
          here: e.g. IP-in-IP-encapsulation, minimal encapsulation or GRE (Generic
          Record Encapsulation)
IP-in-IP-encapsulation (mandatory, RFC 2003)
          tunnel between HA and COA

                       ver.   IHL         TOS                length
                           IP identification       flags   fragment offset
                          TTL           IP-in-IP         IP checksum
                                          IP address of HA
                                       Care-of address COA
                       ver. IHL           TOS                length
                           IP identification       flags   fragment offset
                          TTL         lay. 4 prot.       IP checksum
                                          IP address of CN
                                         IP address of MN
                                         TCP/UDP/ ... payload


Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   59
             Optimization of packet forwarding

Triangular Routing
         sender sends all packets via HA to MN
         higher latency and network load
“Solutions”
         sender learns the current location of MN
         direct tunneling to this location
         HA informs a sender about the location of MN
         big security problems!
Change of FA
         packets on-the-fly during the change can be lost
         new FA informs old FA to avoid packet loss, old FA now forwards
         remaining packets to new FA
         this information also enables the old FA to release resources for the MN




Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   60
             Change of foreign agent

     CN                    HA                   FAold              FAnew                  MN

             Data                    Data                          Data
           Update
                     ACK

                                   Data                            Data                        MN changes
                                                                                               location

                                                        Update             Registration
                                                              ACK
                         Data
                                                         Data                 Data
               Warning
             Request
           Update
                  ACK
                                   Data
                                                                             Data
                                                                                           t

Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School             61
             Reverse tunneling (RFC 3024, was: 2344)

                     HA
                               2
                                                                                               MN



    home network                                                                        sender
                                                                      1
                                        Internet

                                                                               FA foreign
                                                                                     network


                                                        1. MN sends to FA
                        3                               2. FA tunnels packets to HA
      CN                                                   by encapsulation
                                                        3. HA forwards the packet to the
                                                           receiver (standard case)
            receiver

Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School      62
             Mobile IP with reverse tunneling

Router accept often only “topological correct“ addresses (firewall!)
         a packet from the MN encapsulated by the FA is now topological correct
         furthermore multicast and TTL problems solved (TTL in the home network
         correct, but MN is to far away from the receiver)


Reverse tunneling does not solve
         problems with firewalls, the reverse tunnel can be abused to circumvent
         security mechanisms (tunnel hijacking)
         optimization of data paths, i.e. packets will be forwarded through the tunnel
         via the HA to a sender (double triangular routing)


The standard is backwards compatible
         the extensions can be implemented easily and cooperate with current
         implementations without these extensions
         Agent Advertisements can carry requests for reverse tunneling


Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   63
             Mobile IP and IPv6

Mobile IP was developed for IPv4, but IPv6 simplifies the protocols
         security is integrated and not an add-on, authentication of registration is
         included
         COA can be assigned via auto-configuration (DHCPv6 is one candidate),
         every node has address auto configuration
         no need for a separate FA, all routers perform router advertisement which
         can be used instead of the special agent advertisement;
         addresses are always co-located
         MN can signal a sender directly the COA, sending via HA not needed in
         this case (automatic path optimization)
         „soft“ hand-over, i.e. without packet loss, between two subnets is
         supported
               MN sends the new COA to its old router
               the old router encapsulates all incoming packets for the MN and forwards them
               to the new COA
               authentication is always granted



Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   64
             Problems with Mobile IP

Security
         authentication with FA problematic, for the FA typically belongs to another
         organization
         no protocol for key management and key distribution has been
         standardized in the Internet
Firewalls
         typically mobile IP cannot be used together with firewalls, special set-ups
         are needed (such as reverse tunneling)
QoS
         many new reservations in case of RSVP (or similar reservation protocols)
         tunneling makes it hard to give a flow of packets a special treatment
         needed for the QoS


Security, firewalls, QoS etc. are topics of current research and
  discussions!


Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   65
             Manet: Mobile Ad-hoc Networking


   Mobile
   Router

                                                                                      Manet

   Mobile
   Devices

                                                                                      Mobile IP,
                                                                                      DHCP

   Fixed
   Network

                                    Router                      End system




Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/    KuVS-Summer-School   66
             World Wide Web and mobility

     Protocol (HTTP, Hypertext Transfer Protocol) and language
        (HTML, Hypertext Markup Language) of the Web have not been
        designed for mobile applications and mobile devices, thus
        creating many problems!
     Typical transfer sizes
              HTTP request: 100-350 byte
              responses avg. <10 kbyte, header 160 byte, GIF 4.1kByte, JPEG
              12.8 kbyte, HTML 5.6 kbyte
              but also many large files that cannot be ignored
     The Web is no file system
              Web pages are not simple files to download
              static and dynamic content, interaction with servers via forms,
              content transformation, push technologies etc.
              many hyperlinks, automatic loading and reloading, redirecting
              a single click might have big consequences!


Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   67
             HTTP and mobility I

     Characteristics
              stateless, client/server, request/response
              needs a connection oriented protocol (TCP)
              primitive caching and security


     Problems
              designed for large bandwidth (compared to wireless access) and
              low delay
              big and redundant protocol headers (readable for humans,
              stateless, therefore big headers in ASCII)
              uncompressed content transfer
              using standard TCP
                    huge overhead per request (3-way-handshake) compared with the
                    content, e.g., of a GET request
                    slow-start problematic
              DNS lookup by client causes additional traffic

Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   68
             HTTP and mobility II

Caching
         quite often disabled by information providers to be able to create user
         profiles, usage statistics etc.
         dynamic objects cannot be cached
               numerous counters, time, date, personalization, ...
         mobility quite often inhibits caches
         security problems
               how to use SSL/TLS together with proxies?
         today: many user customized pages, dynamically generated on request via
         CGI, ASP, ...


POSTing (i.e., sending to a server)
         can typically not be buffered, very problematic if currently disconnected


Many unsolved problems!


Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   69
             HTML and mobile devices
     HTML
              designed for computers with “high” performance, color high-
              resolution display, mouse, hard disk
              typically, web pages optimized for design, not for communication
     Mobile devices
              often only small, low-resolution displays, very limited input
              interfaces (small touch-pads, soft-keyboards)
     Additional “features”
              animated GIF, Java AWT, Frames, ActiveX Controls, Shockwave,
              movie clips, audio, ...
              many web pages assume true color, multimedia support, high-
              resolution and many plug-ins

     Web pages ignore the heterogeneity of end-systems!
              e.g., without additional mechanisms, large high-resolution pictures
              would be transferred to a mobile phone with a low-resolution
              display causing high costs

Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   70
             Some new issues that might help mobility?

         Push technology
              real pushing, not a client pull needed, channels etc.
         HTTP/1.1
              client/server use the same connection for several request/response
              transactions
              multiple requests at beginning of session, several responses in
              same order
              enhanced caching of responses (useful if equivalent responses!)
              semantic transparency not always achievable: disconnected,
              performance, availability -> most up-to-date version...
              several more tags and options for controlling caching
              (public/private, max-age, no-cache etc.)
              relaxing of transparency on app. request or with warning to user
              encoding/compression mechanism, integrity check, security of
              proxies, authentication, authorization...
         Cookies: well..., stateful sessions, not really integrated...

Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   71
             WAP - Wireless Application Protocol

     Goals
              deliver Internet content and enhanced services to mobile devices and
              users (mobile phones, PDAs)
              independence from wireless network standards
              open for everyone to participate, protocol specifications will be
              proposed to standardization bodies
              applications should scale well beyond current transport media and
              device types and should also be applicable to future developments
     Platforms
              e.g., GSM (900, 1800, 1900), CDMA IS-95, TDMA IS-136, 3rd
              generation systems (IMT-2000, UMTS, W-CDMA)
     Forum
              was: WAP Forum, co-founded by Ericsson, Motorola, Nokia, Unwired
              Planet, further information www.wapforum.org
              now: Open Mobile Alliance www.openmobilealliance.org
              (Open Mobile Architecture + WAP Forum + SyncML + …)

Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   72
             WAP - scope of standardization
     Browser
              “micro browser”, similar to existing, well-known browsers in the
              Internet

     Script language
              similar to Java script, adapted to the mobile environment

     WTA/WTAI
              Wireless Telephony Application (Interface): access to all telephone
              functions

     Content formats
              e.g., business cards (vCard), calendar events (vCalender)

     Protocol layers
              transport layer, security layer, session layer etc.


Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   73
             WAP 1.x - reference model and protocols

      Internet                 A-SAP       WAP

    HTML, Java             Application Layer (WAE)                     additional services
                                                                       and applications
                               S-SAP
                                  Session Layer (WSP)
        HTTP                  TR-SAP
                                     Transaction Layer (WTP)
                             SEC-SAP
      SSL/TLS                               Security Layer (WTLS)
                               T-SAP

       TCP/IP,                                  Transport Layer (WDP)                WCMP
       UDP/IP,
        media                             Bearers (GSM, UMTS, CDPD, ...)

  WAE comprises WML (Wireless Markup Language), WML Script, WTAI etc.


Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School           74
             WAP - network elements


                   fixed network                                     wireless network


                   HTML                  WML       WAP          Binary WML
  Internet
                               filter              proxy


         HTML                            WML
                        HTML
                                                   filter/         Binary WML
                                                   WAP
         web                            HTML       proxy
        server


                                                    WTA         Binary WML
                                                   server
                        PSTN


                                               Binary WML: binary file format for clients

Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School          75
             WDP - Wireless Datagram Protocol

Protocol of the transport layer within the WAP architecture
         uses directly transports mechanisms of different network technologies
         offers a common interface for higher layer protocols
         allows for transparent communication using different transport technologies
         (GSM [SMS, CSD, USSD, GPRS, ...], IS-136, TETRA, DECT, PHS, IS-95,
         ...)


Goals of WDP
         create a worldwide interoperable transport system with the help of WDP
         adapted to the different underlying technologies
         transmission services such as SMS, GPRS in GSM might change, new
         services can replace the old ones


Additionally, WCMP (wireless Control Message Protocol) is used for
  control/error report (similar to ICMP in the TCP/IP protocol suite)


Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   76
             WTLS - Wireless Transport Layer Security

Goals
         data integrity
               prevention of changes in data
         privacy
               prevention of tapping
         authentication
               creation of authenticated relations between a mobile device and a server
         protection against denial-of-service attacks
               protection against repetition of data and unverified data


WTLS
         is based on the TLS (Transport Layer Security) protocol (former SSL,
         Secure Sockets Layer)
         optimized for low-bandwidth communication channels




Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   77
             WTP - Wireless Transaction Protocol

 Goals
          different transaction services, offloads applications
                application can select reliability, efficiency
          support of different communication scenarios
                class 0: unreliable message transfer
                class 1: reliable message transfer without result message
                class 2: reliable message transfer with exactly one reliable result message
          supports peer-to-peer, client/server and multicast applications
          low memory requirements, suited to simple devices (< 10kbyte )
          efficient for wireless transmission
                segmentation/reassembly
                selective retransmission
                header compression
                optimized connection setup (setup with data transfer)




Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   78
             WTP Class 2 transaction, user ack

                                      initiator           responder
                                      TR-SAP               TR-SAP
   TR-Invoke.req
   (SA, SP, DA, DP, A, UD, C=2, H)                              TR-Invoke.ind
                                               Invoke
                                                        PDU     (SA, SP, DA, DP, A, UD, C=2, H‘)
                                                                TR-Invoke.res
                                                                (H‘)
   TR-Invoke.cnf                                     U
   (H)                                         Ack PD           TR-Result.req
                                                                (UD*, H‘)
   TR-Result.ind                                        DU
   (UD*, H)                                    R esult P

   TR-Result.res
   (H)
                                               Ack PD           TR-Result.cnf
                                                     U
                                                                (H‘)




Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School      79
             WSP - Wireless Session Protocol

     Goals
              HTTP 1.1 functionality
                    Request/reply, content type negotiation, ...
              support of client/server, transactions, push technology
              key management, authentication, Internet security services
              session management (interruption, resume,...)


     Open topics
              QoS support
              Group communication
              Isochronous media objects
              management




Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   80
             WAE - Wireless Application Environment
   Goals
            network independent application environment for low-bandwidth,
            wireless devices
            integrated Internet/WWW programming model with high interoperability
   Requirements
            device and network independent, international support
            manufacturers can determine look-and-feel, user interface
            considerations of slow links, limited memory, low computing power, small
            display, simple user interface (compared to desktop computers)
   Components
            architecture: application model, browser, gateway, server
            WML: XML-Syntax, based on card stacks, variables, ...
            WMLScript: procedural, loops, conditions, ... (similar to JavaScript)
            WTA: telephone services, such as call control, text messages, phone
            book, ... (accessible from WML/WMLScript)
            content formats: vCard, vCalendar, Wireless Bitmap, WML, ...

Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   81
             WAE logical model


         Origin Servers                              Gateway                           Client


                                   response                           encoded          WTA
                   web
                                   with                               response       user agent
                  server
                                   content                            with
                                                     encoders
                                                                      content
                                                        &
                                                     decoders                          WML
              other content
                                                                                     user agent
                 server            push                               encoded
                                   content                            push
                                                                      content
                                                                                        other
                                                                                        WAE
                                                                                     user agents
                                   request                            encoded
                                                                      request




Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School        82
             Wireless Markup Language (WML)

WML follows deck and card metaphor
         WML document consists of many cards, cards are grouped to decks
         a deck is similar to an HTML page, unit of content transmission
         WML describes only intent of interaction in an abstract manner
         presentation depends on device capabilities


Features
         text and images
         user interaction
         navigation
         context management




Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   83
             WML – example I

     <?xml version="1.0"?>
     <!DOCTYPE wml PUBLIC "-//WAPFORUM//DTD WML 1.1//EN"
                   "http://www.wapforum.org/DTD/wml_1.1.xml">
     <wml>
         <card id="card_one" title="simple example">
             <do type="accept">
                  <go href="#card_two"/>
             </do>
             <p>
             This is a simple first card!
             <br/>
             On the next one you can choose ...
             </p>
         </card>




Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   84
             WML – example II
<card id="card_two" title="Pizzawahl">
        <do type="accept" label="cont">
             <go href="#card_three"/>
        </do>
        <p>
        ... your favorite pizza!
        <select value="Mar" name="PIZZA">
             <option value="Mar">Margherita</option>
             <option value="Fun">Funghi</option>
             <option value="Vul">Vulcano</option>
        </select>
        </p>
    </card>
    <card id="card_three" title="Your Pizza!">
        <p>
        You personal pizza parameter is <b>$(PIZZA)</b>!
        </p>
    </card>
</wml>

Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   85
             WMLScript

Complement to WML
Provides general scripting capabilities
Features
         validity check of user input
               check input before sent to server
         access to device facilities
               hardware and software (phone call, address book etc.)
         local user interaction
               interaction without round-trip delay
         extensions to the device software
               configure device, download new functionality after deployment




Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   86
             Wireless Telephony Application (WTA)

Collection of telephony specific extensions
Extension of basic WAE application model
         content push
               server can push content to the client
               client may now be able to handle unknown events
         handling of network events
               table indicating how to react on certain events from the network
         access to telephony functions
               any application on the client may access telephony functions
Example
         calling a number (WML)
         wtai://wp/mc;07216086415
         calling a number (WMLScript)
         WTAPublic.makeCall("07216086415");




Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   87
                 Voice box example

 WTA-User-Agent             WTA-Gateway            WTA-Server           Mobile network        Voice box server
                                                         Indicate new voice message
                                                Generate new deck
       Service Indication          Push URL
 Display deck;
 user selects
                  WSP Get         HTTP Get

                                               Respond with content
           Binary WML              WML

 Display deck;
 user selects
                  WSP Get          HTTP Get
                                                Respond with card
                                   WML               for call
           Binary WML
                                                         Play requested voice message
  Wait for call
                                                                                            Call setup
                                                                               Setup call
                                      Setup call
   Accept call
                                 Accept call                                    Accept call
                                                        Voice connection




Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/         KuVS-Summer-School                 88
             Push/Pull services in WAP I

Service Indication
         Service announcement using a pushed short message
         Service usage via a pull
         Service identification via a URI

<?xml version="1.0"?>
  <!DOCTYPE si PUBLIC "-//WAPFORUM//DTD SI 1.0//EN"
    "http://www.wapforum.org/DTD/si.dtd">
<si>
  <indication href="http://www.piiiizza4u.de/offer/salad.wml"
     created="2000-02-29T17:45:32Z"
     si-expires="2000-02-29T17:50:31Z">
     Salad special: The 5 minute offer
  </indication>
</si>


Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   89
             Push/Pull services in WAP II

Service Loading
         short message pushed to a client containing a URI
         User agent decides whether to use the URI via a pull
         Transparent for users, always looks like a push

<?xml version="1.0"?>
  <!DOCTYPE sl PUBLIC "-//WAPFORUM//DTD SL 1.0//EN"
    "http://www.wapforum.org/DTD/sl.dtd">
<sl
  href="http://www.piiiizza4u.de/offer/salad.wml">
</sl>




Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   90
             i-mode – first of all a business model!

Access to Internet services in Japan provided by NTT DoCoMo
         Services
               Email, short messages, web, picture exchange, horoscope, ...
         Big success – more than 30 million users
               Many use i-mode as PC replacement
               For many this is the first Internet contact
               Very simple to use, convenient
         Technology
               9.6 kbit/s (enhancements with 28.8 kbit/s), packet oriented (PDC-P)
               Compact HTML, no security


                        i-mode
                     Email    CHTML
                         HTTP
                          TCP
                           IP
                        PDC-P


Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   91
             Email example: i-mode push with SMS


                                                     Popular misconception:
                 application                         WAP was a failure, i-mode is different
                                                     and (thus) a success – wrong from a
                     WSP                             technology point of view, right from a
                     WTP                             business point of view…

                     WDP

                     SMS                                        i-mode as a business model:
                                                                - content providers get >80%
Operator sends an SMS containing a                                of the revenue.
push message if a new email has                                 - independent of technology
arrived. If the user wants to read the                            (GSM/GPRS in Europe,
email, an HTTP GET follows – with the                             PDC-P in Japan – but also
email as response.                                                UMTS!)



Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School     92
             i-mode protocol stack based on WAP 2.0



                       HTML                                            HTML

                                                                       HTTP
                        HTTP
                                  SSL                                  SSL

                       WTCP                                     WTCP          TCP

                          IP                                     IP           IP

                         L2                                      L2           L2

                         L1                                      L1           L1

                   User Equipment                               Gateway or Server


     i-mode can use WAP protocols (example: i-mode in Germany over GSM/GPRS)




Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   93
                    i-mode – technical requirements

Functions                           Descriptions                                                          Status   Requirement
WEB Access                          Portal Site / Internet Access                                           M      i-mode HTML
E-mail                              Internet e-mail and inter-terminal email                                M      HTTP 1.1
Security                            End-End security                                                        O      SSL (Version2, 3)
Java                                Java application made available                                         O      Compatible i-mode JAVA
Ringing tone download               Ringing melody download                                                 M      SMF based
Image download                      Stand-by screen download                                                M      GIF
Voice call notification during i-   Voice termination notified and responded during i-mode                  M      3GPP standard system
mode session                        communications
Content charge billing              Per content charge billed to user                                       M      Specifications depend on each
                                                                                                                   operator’s billing system
Third party payment collection      Content charge collection on behalf of Content Provider                 M      Specifications depend on each
                                                                                                                   operator’s billing system
Reverse billing                     Packet usage charges can be billed to third party                       O      Specifications depend on each
                                                                                                                   operator’s billing system
Subscriber ID transmission          Hashed subscriber ID from the operator’s portal to the CP               M      The ID generation algorithm
                                    transmission on each content access                                            should be determined by each
                                                                                                                   operator and has to be secret
Number of characters per e-         Number of characters (byte) per e-mail                                  M      To be defined by operators (e.g.
mail                                                                                                               500 byte, 1K byte, 10K byte)
Character code set supported        Character code set supported by browser and used to develop content     M      To be defined by operators
User Agent                          Browser specifications to be notified                                   M      HTTP 1.1
i-mode button                       Dedicated button                                                        O      Hard or soft key



 Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/                           KuVS-Summer-School                     94
             i-mode examples I




Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   95
             i-mode examples II




Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   96
             i-mode examples III




Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   97
             WAP 2.0 (July 2001)

New for developers
         XHTML
         TCP with „Wireless Profile“ (TCP with a certain parameter setting)
         HTTP


New applications
         Color graphics
         Animation
         Large file download
         Location based services
         Synchronization with PIMs
         Pop-up/context sensitive menus


Goal: integration of WWW, Internet, WAP, i-mode


Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   98
                WAP 2.0 architecture

  Service            Security           Multimedia Messaging             Content




                                                                                                           Application
                                                                                                           framework
 discovery           services                  (Email)                   formats

   External            Crypto           WAE/WTA User Agent
                                                                            Push
 services EFI         libraries           (WML, XHTML)

                      Authenti-
 Provisioning                                      Capability Negotiation




                                                                                               Session
                       cation
                                         Push                                        Cookies
  Neighbor                               OTA               Synchronization
                    Identification
  Discovery




                                                                                                                Protocol framework
                                                                                               Transfer
   Service                               Hypermedia transfer          Strea-
                        PKI                                                           MMS
   Lookup                                (WTP+WSP, HTTP)              ming




                                                                                               Transport
                       Secure                                   Connections
                                          Datagrams
                      transport                                   (TCP with
                                         (WDP, UDP)
                                                               wireless profile)


                       Secure           IPv4    CSD      USSD     GUTS         ...




                                                                                               Bearer
                       bearer
                                            IPv6     SMS       FLEX    MPAK           ...



Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/      KuVS-Summer-School                                  99
             Java 2 Platform Micro Edition

„Java-Boom expected“ (?)
         Desktop: over 90% standard PC architecture, Intel x86 compatible,
         typically MS Windows systems
         Do really many people care about platform independent applications?


BUT: Heterogeneous, “small“ devices
         Internet appliances, cellular phones, embedded control, car radios, ...
         Technical necessities (temperature range, form factor, power consumption,
         …) and economic reasons result in different hardware


J2ME
         Provides a uniform platform
         Restricted functionality compared to standard java platform (JVM)




Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   100
             Applications of J2ME

Example cellular phones
         NTT DoCoMo introduced iαppli
         Applications on PDA, mobile phone, ...
         Game download, multimedia applications,
         encryption, system updates
         Load additional functionality with a push on a
         button (and pay for it)!


Embedded control
         Household devices, vehicles, surveillance
         systems, device control
         System update is an important factor




Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   101
             Characteristics and architecture

Java Virtual Machine
         Virtual Hardware (Processor)
                                                                                     Applications
         KVM (K Virtual Machine)
               Min. 128 kByte, typ. 256 kByte                                           Profile
               Optimized for low performance devices                                   (MIDP)
               Might be a co-processor
Configurations                                                                   Configurations
                                                                                 (CDC, CLDC)
         Subset of standard Java libraries depending technical
         hardware parameters (memory, CPU)
                                                                              Java Virtual Machine
         CLDC (Connected Limited Device Configuration)                            (JVM, KVM)
               Basic libraries, input/output, security – describes Java
               support for mobile devices
                                                                               Operating system
Profiles                                                                     (EPOC, Palm, WinCE)
         Interoperability of heterogeneous devices belonging to
         the same category                                                        Hardware
         MIDP (Mobile Information Device Profile)                             (SH4, ARM, 68k, ...)
               Defines interfaces for GUIs, HTTP, application support, …




Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School        102
             Hardware independent development




Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   103
             Summary J2ME

Idea is more than WAP 1.x or i-mode
         Full applications on mobile phones, not only a
         browser
         Includes system updates, end-to-end encryption


Platform independent via virtualization
         As long as certain common interfaces are used
         Not valid for hardware specific functions


Limited functionality compared to JVM
         Thus, maybe an intermediate solution only – until
         embedded systems, mobile phones are as
         powerful as today’s desktop systems




Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   104
             Questions?

Mobile IP

WAP

i-mode

Or:

.NET, CLR, …
OS for mobile devices
…




Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   KuVS-Summer-School   105

								
To top