10.1Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008
Mobile CommunicationsChapter 10: Support for Mobility
• File systems• Data bases• WWW and Mobility • WAP (Wireless Application Protocol), i-mode & Co.
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.2
Mobile, bearable multimedia equipment …
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.3
File systems - Motivation
• Goal• efficient and transparent access to shared files within a
mobile environment while maintaining data consistency
• Problems• limited resources of mobile computers (memory, CPU, ...)• low bandwidth, variable bandwidth, temporary disconnection• high heterogeneity of hardware and software components
(no standard PC architecture)• wireless network resources and mobile computer are not
very reliable• standard file systems (e.g., NFS, network file system) are
very inefficient, almost unusable
• Solutions• replication of data (copying, cloning, caching)• data collection in advance (hoarding, pre-fetching)
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.4
File systems - consistency problems
• THE big problem of distributed, loosely coupled systems• are all views on data the same?• how and when should changes be propagated to what users?
• Weak consistency• many algorithms offering strong consistency (e.g., via
atomic updates) cannot be used in mobile environments• invalidation of data located in caches through a server is
very problematic if the mobile computer is currently not connected to the network
• occasional inconsistencies have to be tolerated, but conflict resolution strategies must be applied afterwards to reach consistency again
• Conflict detection• content independent: version numbering, time-stamps• content dependent: dependency graphs
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.5
File systems for limited connectivity I
• Symmetry• Client/Server or Peer-to-Peer relations• support in the fixed network and/or mobile computers• one file system or several file systems• one namespace for files or several namespaces
• Transparency• hide the mobility support, applications on mobile computers
should not notice the mobility• user should not notice additional mechanisms needed
• Consistency model• optimistic or pessimistic
• Caching and Pre-fetching• single files, directories, subtrees, partitions, ...• permanent or only at certain points in time
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.6
File systems for limited connectivity II
• Data management• management of buffered data and copies of data• request for updates, validity of data• detection of changes in data
• Conflict solving• application specific or general• errors
• Several early experimental systems exist (late 80s)• Coda (Carnegie Mellon University), Little Work (University of
Michigan), Ficus (UCLA) etc.
• Many systems use ideas from distributed file systems such as, e.g., AFS (Andrew File System)
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.7
mobile client
File systems - Coda I
• Application transparent extensions of client and server• changes in the cache manager of a client• applications use cache replicates of files• extensive, transparent collection of data in advance for
possible future use („Hoarding“)
• Consistency• system keeps a record of changes in files and compares files
after reconnection• if different users have changed the same file a manual
reintegration of the file into the system is necessary• optimistic approach, coarse grained (file size)
cacheapplication server
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.8
File systems - Coda II
• Hoarding• user can pre-determine a file
list with priorities• contents of the cache
determined by the list and LRU strategy (Last Recently Used)
• explicit pre-fetching possible• periodic updating
• Comparison of files• asynchronous, background• system weighs speed of
updating against minimization of network traffic
• Cache misses• modeling of user patience: how
long can a user wait for data without an error message?
• function of file size and bandwidth
hoarding
writedisconnected
emulating
disconnection
disconnection
connection
strongconnection
weakconnection
• States of a client
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.9
File systems - Little Work
• Only changes in the cache manager of the client• Connection modes and use
Connected PartiallyConnected
Fetch only Disconnected
Method normal delayed writeto the server
optimisticreplication of files
abort at cachemiss
Networkrequirements
continuoushighbandwidth
continuousbandwidth
connection ondemand
none
Application office, WLAN packet radio cellular systems(e.g., GSM) withcosts per call
independent
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.10
File systems - further examples
• Mazer/Tardo• file synchronization layer between application and local file system• caching of complete subdirectories from the server• “Redirector” responses to requests locally if necessary, via the
network if possible• periodic consistency checks with bi-directional updating
• Ficus• not a client/server approach• optimistic approach based on replicates, detection of write conflicts,
conflict resolution• use of „gossip“ protocols: a mobile computer does not necessarily
need to have direct connection to a server, with the help of other mobile computers updates can be propagated through the network
• MIo-NFS (Mobile Integration of NFS)• NFS extension, pessimistic approach, only token holder can write• connected/loosely connected/disconnected
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.11
Database systems in mobile environments
• Request processing• power conserving, location dependent, cost efficient• example: find the fastest way to a hospital
• Replication management• similar to file systems
• Location management• tracking of mobile users to provide replicated or location
dependent data in time at the right place (minimize access delays)
• example: with the help of the HLR (Home Location Register) in GSM a mobile user can find a local towing service
• Transaction processing• “mobile” transactions can not necessarily rely on the same
models as transactions over fixed networks (ACID: atomicity, consistency, isolation, durability)
• therefore models for “weak” transaction
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.12
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 H. Schiller www.jochenschiller.de MC - 2008 10.13
WWW exampleRequest to port 80: GET / HTTP/1.0or: GET / HTTP/1.1
Host: www.inf.fu-berlin.deResponse from serverHTTP/1.1 200 OKDate: Wed, 30 Oct 2002 19:44:26 GMTServer: Apache/1.3.12 (Unix) mod_perl/1.24Last-Modified: Wed, 30 Oct 2002 13:16:31 GMTETag: "2d8190-2322-3dbfdbaf"Accept-Ranges: bytesContent-Length: 8994Connection: closeContent-Type: text/html
<DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>
<head><title>FU-Berlin: Institut für Informatik</TITLE><base href="http://www.inf.fu-berlin.de"><link rel="stylesheet" type="text/css" href="http://www.inf.fu-berlin.de/styles/homepage.css"><!--script language="JavaScript" src="fuinf.js"--><!--/script-->
</head>
<body onResize="self.location.reload();">...
non persistent
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.14
HTTP 1.0 (old) and mobility I
• Characteristics• stateless, client/server, request/response• needs a connection oriented protocol (TCP), one connection
per request (some enhancements in HTTP 1.1)• 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 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 H. Schiller www.jochenschiller.de MC - 2008 10.15
HTTP 1.0 (old) 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 H. Schiller www.jochenschiller.de MC - 2008 10.16
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 H. Schiller www.jochenschiller.de MC - 2008 10.17
Approaches toward WWW for mobile devices
• Application gateways, enhanced servers• simple clients, pre-calculations in the fixed network• compression, filtering, content extraction• automatic adaptation to network characteristics
• Examples• picture scaling, color reduction, transformation of the document
format (e.g., PS to TXT)• detail studies, clipping, zoom • headline extraction, automatic abstract generation• HDML (handheld device markup language): simple language similar
to HTML requiring a special browser• HDTP (handheld device transport protocol): transport protocol for
HDML, developed by Unwired Planet
• Problems• proprietary approaches, require special enhancements for browsers• heterogeneous devices make approaches more complicated
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.18
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 H. Schiller www.jochenschiller.de MC - 2008 10.19
mobile client
browser
integratedenhancement
System support for WWW in a mobile world I (some historical)
• Enhanced browsers• Pre-fetching, caching, off-line use• e.g. Internet Explorer
• Additional, accompanying application• Pre-fetching, caching, off-line use• e.g. original WebWhacker
webserver
mobile client
browseradditionalapplication
webserver
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.20
System support for WWW in a mobile world II (some historical)
• Client Proxy• Pre-fetching, caching, off-line use• e.g., Caubweb, TeleWeb, Weblicator,
WebWhacker, WebEx, WebMirror,...
• Network Proxy• adaptive content transformation
for bad connections, pre-fetching, caching
• e.g., TranSend, Digestor
mobile client
browser
networkproxy
webserver
mobile client
browserclientproxy
webserver
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.21
System support for WWW in a mobile world III (some historical)
• Client and network proxy• combination of benefits plus
simplified protocols• e.g., MobiScape, WebExpress
• Special network subsystem• adaptive content transformation
for bad connections, pre-fetching, caching
• e.g., Mowgli
• Additional many proprietary serverextensions possible• “channels”, content negotiation, ...
mobile client
browser
webserver
mobile client
browser clientproxy
webserver
networkproxy
clientproxy
networkproxy
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.22
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, cdma2000 1x EV-DO, …)
• 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 H. Schiller www.jochenschiller.de MC - 2008 10.23
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 H. Schiller www.jochenschiller.de MC - 2008 10.24
WAP 1.x - reference model and protocols
Bearers (GSM, CDPD, ...)
Security Layer (WTLS)
Session Layer (WSP)
Application Layer (WAE)
Transport Layer (WDP)TCP/IP,UDP/IP,media
SSL/TLS
HTML, Java
HTTP
Internet WAP
WAE comprises WML (Wireless Markup Language), WML Script, WTAI etc.
Transaction Layer (WTP)
additional services and applications
WCMP
A-SAP
S-SAP
TR-SAP
SEC-SAP
T-SAP
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.25
WAP - network elements
wireless networkfixed network
WAPproxy
WTAserver
filter/WAPproxyweb
server
filter
PSTN
Internet
Binary WML: binary file format for clients
Binary WML
Binary WML
Binary WML
HTML
HTML
HTML WML
WMLHTML
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.26
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 protocolsuite)
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.27
WDP - Service Primitives
T-SAP T-SAPT-DUnitdata.req(DA, DP, SA, SP, UD) T-DUnitdata.ind
(SA, SP, UD) T-DUnitdata.req(DA, DP, SA, SP, UD)
T-DError.ind(EC)
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.28
Usage of WDP
GSM-SMS
GSM-CSD
WTLSWTLS
WDP &Adaptation
WDP &Adaptation
SMSSMS
Wireless Data GatewayWTLSWTLS
WDP &Adaptation
WDP &Adaptation
TunnelTunnel
SubnetworkSubnetwork
SMSSMS TunnelTunnel
SubnetworkSubnetwork
WAPProxy
WTLSWTLS
UDPUDP
WTLSWTLS
UDPUDP
IPIP
PPPPPP
CSD-RFCSD-RF
IPIP
SubnetworkSubnetwork
IPIP
PPPPPP
CSD-RFCSD-RF PSTNCircuitPSTNCircuit
SubnetworkSubnetwork
InterworkingFunction
Internet Service ProviderRemote Access Service
PSTNCircuitPSTNCircuit
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.29
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 H. Schiller www.jochenschiller.de MC - 2008 10.30
Secure session, full handshake
SEC-Create.req(SA, SP, DA, DP, KES, CS, CM)
SEC-Create.ind(SA, SP, DA, DP, KES, CS, CM)
originatorSEC-SAP
peerSEC-SAP
SEC-Create.cnf(SNM, KR, SID, KES‘, CS‘, CM‘)
SEC-Create.res(SNM, KR, SID, KES‘, CS‘, CM‘)
SEC-Exchange.req
SEC-Exchange.ind
SEC-Exchange.res(CC)SEC-Commit.req SEC-Exchange.cnf
(CC)SEC-Commit.ind
SEC-Commit.cnf
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.31
SEC-Unitdata - transferring datagrams
SEC-Unitdata.req(SA, SP, DA, DP, UD) SEC-Unitdata.ind
(SA, SP, DA, DP, UD)
senderSEC-SAP
receiverSEC-SAP
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.32
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 H. Schiller www.jochenschiller.de MC - 2008 10.33
Details of WTP I
• Support of different communication scenarios
• Class 0: unreliable message transfer• Example: push service
• Class 1: reliable request• An invoke message is not followed by a result message• Example: reliable push service
• Class 2: reliable request/response• An invoke message is followed by exactly one result message• With and without ACK• Example: typical web browsing
• No explicit connection setup or release is available
• Services for higher layers are called events
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.34
Details of WTP II
• Used Mechanisms• Reliability
• Unique transaction identifiers (TID)• Acknowledgements• Selective retransmission• Duplicate removal
• Optional: concatenation & separation of messages• Optional: segmentation & reassembly of messages• Asynchronous transactions• Transaction abort, error handling• Optimized connection setup (includes data transmission)
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.35
WTP Class 0 transaction
TR-Invoke.req(SA, SP, DA, DP, A, UD, C=0, H) Invoke PDU
TR-Invoke.ind(SA, SP, DA, DP, A, UD, C=0, H‘)
initiatorTR-SAP
responderTR-SAP
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.36
WTP Class 1 transaction, no user ack& user ack
TR-Invoke.req(SA, SP, DA, DP, A, UD, C=1, H) Invoke PDU
TR-Invoke.ind(SA, SP, DA, DP, A, UD, C=1, H‘)
initiatorTR-SAP
responderTR-SAP
Ack PDU
TR-Invoke.req(SA, SP, DA, DP, A, UD, C=1, H) Invoke PDU
TR-Invoke.ind(SA, SP, DA, DP, A, UD, C=1, H‘)
initiatorTR-SAP
responderTR-SAP
Ack PDU
TR-Invoke.res(H‘)
TR-Invoke.cnf(H)
TR-Invoke.cnf(H)
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.37
WTP Class 2 transaction, no user ack, no hold on
TR-Invoke.req(SA, SP, DA, DP, A, UD, C=2, H) Invoke PDU
TR-Invoke.ind(SA, SP, DA, DP, A, UD, C=2, H‘)
initiatorTR-SAP
responderTR-SAP
Result PDU
TR-Result.req(UD*, H‘)
TR-Result.ind(UD*, H)
Ack PDU
TR-Invoke.cnf(H)
TR-Result.res(H)
TR-Result.cnf(H‘)
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.38
WTP Class 2 transaction, user ack
TR-Invoke.req(SA, SP, DA, DP, A, UD, C=2, H) Invoke PDU
TR-Invoke.ind(SA, SP, DA, DP, A, UD, C=2, H‘)
initiatorTR-SAP
responderTR-SAP
Result PDUTR-Result.ind(UD*, H)
Ack PDU
TR-Invoke.res(H‘)
TR-Invoke.cnf(H) Ack PDU
TR-Result.req(UD*, H‘)
TR-Result.res(H)
TR-Result.cnf(H‘)
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.39
WTP Class 2 transaction, hold on, no user ack
TR-Invoke.req(SA, SP, DA, DP, A, UD, C=2, H) Invoke PDU
TR-Invoke.ind(SA, SP, DA, DP, A, UD, C=2, H‘)
initiatorTR-SAP
responderTR-SAP
Result PDU
TR-Result.req(UD*, H‘)
TR-Result.ind(UD*, H)
Ack PDU
Ack PDUTR-Invoke.cnf(H)
TR-Result.res(H)
TR-Result.cnf(H‘)
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.40
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 H. Schiller www.jochenschiller.de MC - 2008 10.41
WSP protocols
WSP
Connectionless mode(uses WDP or WTLS)
Connection mode(uses WTP)
• Session Management (class 0, 2)
• Method Invocation (Kl. 2)
• Error Report
• Push (class 0)
• Confirmed Push (class 1)
• Session suspend/resume (class 0, 2)
• Method Invocation
• Push
(in general unreliable)
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.42
WSP/B session establishment
S-Connect.req(SA, CA, CH, RC) Connect PDU
S-Connect.ind(SA, CA, CH, RC)
clientS-SAP
serverS-SAP
ConnReply PDU
S-Connect.res(SH, NC)
S-Connect.cnf(SH, NC)
WTP Class 2transaction
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.43
WSP/B session suspend/resume
S-Suspend.req Suspend PDUS-Suspend.ind(R)
clientS-SAP
serverS-SAP
Reply PDUS-Resume.res
WTP Class 2transaction
S-Suspend.ind(R)
~ ~S-Resume.req(SA, CA) S-Resume.ind
(SA, CA)Resume PDU
S-Resume.cnf
WTP Class 0transaction
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.44
WSP/B session termination
Disconnect PDUS-Disconnect.ind(R)
clientS-SAP
serverS-SAP
S-Disconnect.ind(R) WTP Class 0
transaction
S-Disconnect.req(R)
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.45
WSP/B method invoke
S-MethodInvoke.req(CTID, M, RU) Method PDU
S-MethodInvoke.ind(STID, M, RU)
clientS-SAP
serverS-SAP
Reply PDU
S-MethodInvoke.res(STID)
S-MethodInvoke.cnf(CTID)
WTP Class 2transaction
S-MethodResult.req(STID, S, RH, RB)
S-MethodResult.ind(CTID, S, RH, RB)
S-MethodResult.res(CTID) S-MethodResult.cnf
(STID)
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.46
WSP/B over WTP - method invocation
S-MethodInvoke.reqS-MethodInvoke.ind
clientS-SAP
serverS-SAP
S-MethodInvoke.res
S-MethodInvoke.cnfS-MethodResult.req
S-MethodResult.ind
S-MethodResult.resS-MethodResult.cnf
TR-Invoke.req
initiatorTR-SAP
TR-Result.ind
TR-Invoke.cnf
TR-Result.res
TR-Invoke.ind
responderTR-SAP
TR-Invoke.res
TR-Result.req
TR-Result.cnf
Invoke(Method)
Result(Reply)
Ack PDU
Ack PDU
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.47
WSP/B over WTP - asynchronous, unordered requests
S-MethodInvoke_1.req
S-MethodInvoke_1.ind
clientS-SAP
serverS-SAP
S-MethodInvoke_2.req
S-MethodInvoke_3.req
S-MethodResult_1.ind
S-MethodInvoke_4.req
S-MethodResult_3.ind
S-MethodResult_4.ind
S-MethodResult_2.ind
S-MethodInvoke_3.ind
S-MethodInvoke_2.ind
S-MethodResult_1.req
S-MethodResult_2.reqS-MethodResult_3.req
S-MethodResult_4.reqS-MethodInvoke_4.ind
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.48
WSP/B - confirmend/non-confirmed push
S-Push.req(PH, PB)
clientS-SAP
serverS-SAP
ConfPush PDU
WTP Class 1transaction
S-Push.ind(PH, PB)
S-ConfirmedPush.res(CPID)
S-ConfirmedPush.ind(CPID, PH, PB)
WTP Class 0transaction
Push PDU
S-ConfirmedPush.req(SPID, PH, PB)
clientS-SAP
serverS-SAP
S-ConfirmedPush.cnf(SPID)
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.49
WSP/B over WDP
S-Unit-MethodInvoke.req(SA, CA, TID, M, RU)
clientS-SAP
serverS-SAP
S-Unit-MethodResult.ind(CA, SA, TID, S, RH, RB)
S-Unit-Push.ind(CA, SA, PID, PH, PB)
S-Unit-MethodInvoke.ind(SA, CA, TID, M, RU)
S-Unit-MethodResult.req(CA, SA, TID, S, RH, RB)
S-Unit-Push.req(CA, SA, PID, PH, PB)
Method PDU
Reply PDU
Push PDU
WDP Unitdataservice
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.50
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 H. Schiller www.jochenschiller.de MC - 2008 10.51
Origin Servers
WAE logical model
webserver
other contentserver
Gateway Client
otherWAE
user agents
WMLuser agent
WTAuser agent
encoders&
decoders
encodedrequest
encodedresponsewithcontent
request
responsewithcontent
pushcontent
encodedpushcontent
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.52
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 H. Schiller www.jochenschiller.de MC - 2008 10.53
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 H. Schiller www.jochenschiller.de MC - 2008 10.54
WML – example II
<card id="card_two" title="Pizza selection"><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>Your personal pizza parameter is <b>$(PIZZA)</b>!</p>
</card></wml>
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.55
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 H. Schiller www.jochenschiller.de MC - 2008 10.56
WMLScript - example
function pizza_test(pizza_type) {
var taste = "unknown";if (pizza_type = "Margherita") {
taste = "well... ";
}else {
if (pizza_type = "Vulcano") {
taste = "quite hot";};
};
return taste;};
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.57
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 H. Schiller www.jochenschiller.de MC - 2008 10.58
WTA logical architecture
otherservers
client
repository
WTAuser agent
WAP gateway
encoders&
decoders
other telephone networksWTA server
WTA & WMLserver
WMLscripts
WMLdecks
WTAservices
mobilenetwork
firewallthird partyservers
network operatortrusted domain
devicespecific
functions
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.59
Voice box example
Service Indication
WTA-User-Agent WTA-Server Mobile network Voice box server
Generate new deck
Display deck;user selects
Call setup
Accept call
Voice connection
Indicate new voice message
Play requested voice message
Setup call
Accept call Accept call
WTA-Gateway
Push URL
Display deck;user selects WSP Get HTTP Get
Respond with contentWMLBinary WML
WSP Get HTTP GetRespond with card
for callWMLBinary WML
Wait for call
Setup call
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.60
WTAI - example with WML only<?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="Tele voting"><do type="accept">
<go href="#card_two"/></do><p> Please choose your candidate! </p>
</card><card id="card_two" title="Your selection">
<do type="accept"><go href="wtai://wp/mc;$dialno"/>
</do><p> Your selection:<select name="dialno">
<option value="01376685">Mickey</option><option value="01376686">Donald</option><option value="01376687">Pluto</option>
</select></p>
</card></wml>
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.61
WTAI - example with WML and WMLScript I
function voteCall(Nr) {
var j = WTACallControl.setup(Nr,1);if (j>=0) {
WMLBrowser.setVar("Message", "Called");
WMLBrowser.setVar("No", Nr);}else {
WMLBrowser.setVar("Message", "Error!");WMLBrowser.setVar("No", j);
}
WMLBrowser.go("showResult");}
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.62
WTAI - example with WML and WMLScript II<?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="Tele voting"><do type="accept"> <go href="#card_two"/> </do><p> Please choose your candidate! </p>
</card><card id="card_two" title="Your selection">
<do type="accept"><go href="/myscripts#voteCall($dialno)"/> </do>
<p> Your selection:<select name="dialno">
<option value="01376685">Mickey</option><option value="01376686">Donald</option><option value="01376687">Pluto</option>
</select> </p></card><card id="showResult" title="Result">
<p> Status: $Message $No </p></card>
</wml>
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.63
WAP push architecture with proxy gateway
• Push Access Protocol• Content transmission between server and PPG• First version uses HTTP
• Push OTA (Over The Air) Protocol• Simple, optimized• Mapped onto WSP
Client
User Agents
Push Proxy Gateway
Coding,checking
Push OTAProtocol
Push Initiator
PushAccessProtocol
Serverapplication
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.64
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="2007-10-30T17:45:32Z"si-expires="2007-10-30T17:50:31Z">Salad special: The 5 minute offer
</indication></si>
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.65
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 H. Schiller www.jochenschiller.de MC - 2008 10.66
Examples for WAP protocol stacks (WAP 1.x)
WAE
WSP
WTP
UDP
IP(GPRS, ...)
WDP
non IP(SMS, ...)
WTLS
WAE user agentWAP standardization
outside WAP
WTP
UDP
IP(GPRS, ...)
WDP
non IP(SMS, ...)
WTLS
UDP
IP(GPRS, ...)
WDP
non IP(SMS, ...)
WTLS
transaction basedapplication
datagram basedapplication
typical WAP application with
complete protocol stack
pure data application with/without
additional security
3.1. 2.
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.67
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 (in some countries) – millions of users• Many use i-mode as PC replacement• For many this was 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 plus proprietary tags, special transport layer (Stop/go,
ARQ, push, connection oriented)
PDC-P
TLHTTP(S)
cHTML + tags
mobile terminal
PDC-P
TL
mobile network gateway content provider
L1L2IP
TCP
L1L2IP
TCP
L1L2IP
TCP
L1L2IP
TCPHTTP(S)
cHTML + tags
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.68
Email example: i-mode push with SMS
application
WSP
WTP
WDP
SMS
Operator sends an SMS containing a push message if a new email has arrived. If the user wants to read the email, an HTTP get follows with the email as response.
Popular misconception:WAP was a failure, i-mode is different and a success – wrong from a technology point of view, right from a business point of view…
i-mode as a business model:- content providers get >80%of the revenue.
- independent of technology(GSM/GPRS in Europe,PDC-P in Japan – but alsoUMTS!)
- not successful in e.g.Germany (stopped in 2008)
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.69
i-mode protocol stack based on WAP 2.0
user equipment gateway
i-mode can use WAP 2.0/Internet protocols (example: i-mode in Germany over GSM/GPRS)
server
cHTML
HTTP
WTCP
IP
L2
L1
SSL
WTCP
IP
L2
L1
TCP
IP
L2
L1
cHTML
HTTPSSL
TCP
IP
L2
L1
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.70
i-mode – technical requirementsFunctions Descriptions Status Requirement
WEB Access Portal Site / Internet Access M i-mode HTML (cHTML+tags)
E-mail Internet e-mail and inter-terminal email M HTTP 1.1
Security End-End security O SSL (Version 2, 3), TLS 1
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 (O: JPEG)
Voice call notification during i-mode session
Voice termination notified and responded during i-mode communications
M 3GPP standard system
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 transmission on each content access
M The ID generation algorithm should be determined by each operator and has to be secret
Number of characters per e-mail
Number of characters (byte) per e-mail M To be defined by operators (e.g. 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 H. Schiller www.jochenschiller.de MC - 2008 10.71
i-mode – very first examples I
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.72
i-mode – very first examples II
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.73
i-mode – very first examples III
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.74
WAP 2.0 (July 2001)
• New for developers• XHTML• TCP with “Wireless Profile”• 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 H. Schiller www.jochenschiller.de MC - 2008 10.75
WAP 2.0 architecture
Servicediscovery
Securityservices
App
licat
ion
fram
ewor
kP
roto
col f
ram
ewor
k
External services EFI
Provisioning
NavigationDiscovery
ServiceLookup
Cryptolibraries
Authenti-cation
Identification
PKI
Securetransport
Securebearer
Ses
sion
Tran
sfer
Tran
spor
tBe
arer
Multimedia Messaging (Email)
WAE/WTA User Agent (WML, XHTMLMP)
Content formats
Push
IPv4
IPv6
CSD
SMS
USSD
FLEX
GPRS
MPAK
...
...
Datagrams(WDP, UDP)
Connections(TCP with
wireless profile)
Hypermedia transfer (WTP+WSP, HTTP)
Strea-ming MMS
PushOTA
Capability Negotiation
SynchronisationCookies
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.76
WAP 2.0 example protocol stacks
bearerWDPWTLSWTPWSPWAE
WAP device
bearerWDPWTLSWTPWSP
IPTCPTLS
HTTP
IPTCPTLS
HTTP
WAEWeb serverWAP gateway
WAP 1.x Server/Gateway/Client
IPTCP‘TLS
HTTPWAE
WAP device
IPTCP‘
IPTCP
IPTCPTLS
HTTPWAE
Web serverWAP proxy
WAP Proxy with TLS tunneling
IPTCP‘
HTTP‘WAE
WAP device
IPTCP‘
IPTCP
IPTCP
WAEWeb serverWAP proxy
WAP HTTP Proxy with profiled TCP and HTTP
HTTP‘ HTTP HTTP
IPTCP
HTTPWAE
WAP device
IP IP IPTCP
WAEWeb server
IP router
WAP direct access
HTTP
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.77
Java 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
• Java ME (source released as: phone ME / was: J2ME)• Provides a uniform platform• Restricted functionality compared to standard java platform (JVM)
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.78
Applications of Java ME
• Example first 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 H. Schiller www.jochenschiller.de MC - 2008 10.79
Characteristics and architecture
• Java Virtual Machine• Virtual Hardware (Processor)• KVM (K Virtual Machine)
• Min. 128 kByte, typ. 256 kByte• Optimized for low performance devices• Might be a co-processor
• Configurations• Subset of standard Java libraries depending
technical hardware parameters (memory, CPU)
• CLDC (Connected Limited Device Configuration)
• Basic libraries, input/output, security –describes Java support for mobile devices
• Profiles• Interoperability of heterogeneous devices
belonging to the same category• MIDP (Mobile Information Device Profile)
• Defines interfaces for GUIs, HTTP, application support, … -> MIDlets
Hardware(SH4, ARM, 68k, ...)
Java Virtual Machine(JVM, KVM)
Operating system(EPOC, Palm, WinCE)
Configurations(CDC, CLDC)
Profile(MIDP)
Applications
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.80
Hardware independent development
Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2008 10.81
Summary Java ME
• 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 H. Schiller www.jochenschiller.de MC - 2008 10.82
Other mobile application platforms
• Microsoft .NET Compact Framework• run-time environment plus class library with focus on mobile
devices – light-weight version of .NET• support of many programming languages (C#, Python,
Ruby, C++, Haskell, …)• typically in connection with Windows CE
• Qualcomm BREW (Binary Runtime Environment for Wireless)• run-time environment with main focus on games• certified applications only
• Google Android• OS + middleware + applications for mobile devices• Java/Linux based, open source