Transcript Mobile Communications

Mobile Communications
Chapter 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
10.1
Mobile, bearable multimedia
equipment …
Prof. Dr.-Ing. Jochen H. Schiller
www.jochenschiller.de
MC - 2008
10.2
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
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MC - 2008
10.3
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
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MC - 2008
10.4
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
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MC - 2008
10.5
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)
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MC - 2008
10.6
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)
mobile client
application
Prof. Dr.-Ing. Jochen H. Schiller
cache
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server
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10.7
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
• States of a client
hoarding
disconnection
weak
connection
write
disconnected
connection
• Cache misses
disconnection
• modeling of user patience: how
long can a user wait for data
without an error message?
• function of file size and
bandwidth
Prof. Dr.-Ing. Jochen H. Schiller
strong
connection
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emulating
MC - 2008
10.8
File systems - Little Work
• Only changes in the cache manager of the client
• Connection modes and use
Connected
Method
normal
Partially
Connected
delayed write
to the server
continuous
bandwidth
Network
continuous
requirements high
bandwidth
Application
office, WLAN packet radio
Prof. Dr.-Ing. Jochen H. Schiller
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Fetch only
Disconnected
optimistic
replication of files
connection on
demand
abort at cache
miss
none
cellular systems
(e.g., GSM) with
costs per call
independent
MC - 2008
10.9
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
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MC - 2008
10.10
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
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MC - 2008
10.11
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!
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10.12
WWW example
Request to port 80:
or:
GET / HTTP/1.0
GET / HTTP/1.1
Host: www.inf.fu-berlin.de
Response from server
HTTP/1.1 200 OK
Date: Wed, 30 Oct 2002 19:44:26 GMT
Server: Apache/1.3.12 (Unix) mod_perl/1.24
Last-Modified: Wed, 30 Oct 2002 13:16:31 GMT
ETag: "2d8190-2322-3dbfdbaf"
Accept-Ranges: bytes
Content-Length: 8994
Connection: close
Content-Type: text/html
non persistent
<DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>FU-Berlin: Institut f&uuml;r 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();">
...
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10.13
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
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MC - 2008
10.14
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
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MC - 2008
10.15
HTML and mobile devices
• HTML
• designed for computers with “high” performance, color highresolution 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, highresolution 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
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MC - 2008
10.16
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
10.17
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...
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www.jochenschiller.de
MC - 2008
10.18
System support for WWW in a mobile
world I (some historical)
• Enhanced browsers
mobile client
• Pre-fetching, caching, off-line use
• e.g. Internet Explorer
integrated
enhancement
browser
web
server
• Additional, accompanying application
• Pre-fetching, caching, off-line use
• e.g. original WebWhacker
mobile client
browser
additional
application
web
server
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MC - 2008
10.19
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,
...
mobile client
browser
client
proxy
web
server
• Network Proxy
• adaptive content transformation
for bad connections, pre-fetching,
caching
• e.g., TranSend, Digestor
mobile client
browser
network
proxy
web
server
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10.20
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 server
extensions possible
• “channels”, content negotiation, ...
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mobile client
browser
client
proxy
web
server
network
proxy
mobile client
browser
client
proxy
web
server
network
proxy
MC - 2008
10.21
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 EVDO, …)
• 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 + …)
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MC - 2008
10.22
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.
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MC - 2008
10.23
WAP 1.x - reference model and
protocols
Internet
HTML, Java
A-SAP
WAP
additional services
and applications
Application Layer (WAE)
S-SAP
Session Layer (WSP)
HTTP
TR-SAP
Transaction Layer (WTP)
SEC-SAP
SSL/TLS
Security Layer (WTLS)
T-SAP
TCP/IP,
UDP/IP,
media
Transport Layer (WDP)
WCMP
Bearers (GSM, CDPD, ...)
WAE comprises WML (Wireless Markup Language), WML Script, WTAI etc.
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10.24
WAP - network elements
fixed network
Internet
HTML
wireless network
WML
HTML
filter
WAP
proxy
Binary WML
WML
HTML
web
server
HTML
filter/
WAP
proxy
WTA
server
Binary WML
Binary WML
PSTN
Binary WML: binary file format for clients
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MC - 2008
10.25
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)
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MC - 2008
10.26
WDP - Service Primitives
T-SAP
T-DUnitdata.req
(DA, DP, SA, SP, UD)
T-SAP
T-DUnitdata.ind
(SA, SP, UD)
T-DUnitdata.req
(DA, DP, SA, SP, UD)
T-DError.ind
(EC)
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10.27
Usage of WDP
Wireless Data Gateway
WTLS
WDP &
Adaptation
SMS
GSM-SMS
Tunnel
WTLS
WDP &
Adaptation
Tunnel
Subnetwork
Subnetwork
SMS
WAP
Proxy
GSM-CSD
WTLS
Internet Service Provider
Remote Access Service
UDP
IP
PPP
CSD-RF
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Interworking
Function
CSD-RF
PSTN
Circuit
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IP
PPP
PSTN
Circuit
Subnetwork
MC - 2008
WTLS
UDP
IP
Subnetwork
10.28
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
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10.29
Secure session, full handshake
originator
SEC-SAP
SEC-Create.req
(SA, SP, DA, DP, KES, CS, CM)
peer
SEC-SAP
SEC-Create.ind
(SA, SP, DA, DP, KES, CS, CM)
SEC-Create.res
(SNM, KR, SID, KES‘, CS‘, CM‘)
SEC-Create.cnf
(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
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MC - 2008
10.30
SEC-Unitdata - transferring
datagrams
sender
SEC-SAP
receiver
SEC-SAP
SEC-Unitdata.req
(SA, SP, DA, DP, UD)
Prof. Dr.-Ing. Jochen H. Schiller
SEC-Unitdata.ind
(SA, SP, DA, DP, UD)
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MC - 2008
10.31
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
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MC - 2008
10.32
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
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MC - 2008
10.33
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)
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MC - 2008
10.34
WTP Class 0 transaction
initiator
TR-SAP
responder
TR-SAP
TR-Invoke.req
(SA, SP, DA, DP, A, UD, C=0, H)
Prof. Dr.-Ing. Jochen H. Schiller
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TR-Invoke.ind
(SA, SP, DA, DP, A, UD, C=0, H‘)
MC - 2008
10.35
WTP Class 1 transaction, no user ack
& user ack
initiator
TR-SAP
TR-Invoke.req
(SA, SP, DA, DP, A, UD, C=1, H)
responder
TR-SAP
TR-Invoke.ind
(SA, SP, DA, DP, A, UD, C=1, H‘)
TR-Invoke.cnf
(H)
initiator
TR-SAP
TR-Invoke.req
(SA, SP, DA, DP, A, UD, C=1, H)
TR-Invoke.ind
(SA, SP, DA, DP, A, UD, C=1, H‘)
TR-Invoke.res
(H‘)
TR-Invoke.cnf
(H)
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responder
TR-SAP
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MC - 2008
10.36
WTP Class 2 transaction, no user ack,
no hold on
initiator
TR-SAP
TR-Invoke.req
(SA, SP, DA, DP, A, UD, C=2, H)
responder
TR-SAP
TR-Invoke.ind
(SA, SP, DA, DP, A, UD, C=2, H‘)
TR-Result.req
(UD*, H‘)
TR-Invoke.cnf
(H)
TR-Result.ind
(UD*, H)
TR-Result.res
(H)
Prof. Dr.-Ing. Jochen H. Schiller
TR-Result.cnf
(H‘)
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MC - 2008
10.37
WTP Class 2 transaction, user ack
initiator
TR-SAP
TR-Invoke.req
(SA, SP, DA, DP, A, UD, C=2, H)
TR-Invoke.ind
(SA, SP, DA, DP, A, UD, C=2, H‘)
TR-Invoke.res
(H‘)
TR-Invoke.cnf
(H)
TR-Result.req
(UD*, H‘)
TR-Result.ind
(UD*, H)
TR-Result.res
(H)
Prof. Dr.-Ing. Jochen H. Schiller
responder
TR-SAP
TR-Result.cnf
(H‘)
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MC - 2008
10.38
WTP Class 2 transaction, hold on, no
user ack
initiator
TR-SAP
TR-Invoke.req
(SA, SP, DA, DP, A, UD, C=2, H)
TR-Invoke.cnf
(H)
responder
TR-SAP
TR-Invoke.ind
(SA, SP, DA, DP, A, UD, C=2, H‘)
TR-Result.req
(UD*, H‘)
TR-Result.ind
(UD*, H)
TR-Result.res
(H)
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TR-Result.cnf
(H‘)
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MC - 2008
10.39
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
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10.40
WSP protocols
WSP
Connection mode
(uses WTP)
Connectionless mode
(uses WDP or WTLS)
• Session Management (class 0, 2)
• Method Invocation
• Method Invocation (Kl. 2)
• Push
• Error Report
(in general unreliable)
• Push (class 0)
• Confirmed Push (class 1)
• Session suspend/resume (class 0, 2)
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10.41
WSP/B session establishment
client
S-SAP
server
S-SAP
S-Connect.req
(SA, CA, CH, RC)
S-Connect.ind
(SA, CA, CH, RC)
S-Connect.res
(SH, NC)
S-Connect.cnf
(SH, NC)
WTP Class 2
transaction
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MC - 2008
10.42
WSP/B session suspend/resume
client
S-SAP
server
S-SAP
S-Suspend.req
S-Suspend.ind
(R)
S-Suspend.ind
(R)
S-Resume.req
(SA, CA)
WTP Class 0
transaction
~
~
S-Resume.ind
(SA, CA)
S-Resume.res
S-Resume.cnf
WTP Class 2
transaction
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10.43
WSP/B session termination
client
S-SAP
server
S-SAP
S-Disconnect.req
(R)
S-Disconnect.ind
(R)
Prof. Dr.-Ing. Jochen H. Schiller
S-Disconnect.ind
(R)
WTP Class 0
transaction
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MC - 2008
10.44
WSP/B method invoke
client
S-SAP
server
S-SAP
S-MethodInvoke.req
(CTID, M, RU)
S-MethodInvoke.ind
(STID, M, RU)
S-MethodInvoke.res
(STID)
S-MethodInvoke.cnf
(CTID)
S-MethodResult.req
(STID, S, RH, RB)
S-MethodResult.ind
(CTID, S, RH, RB)
S-MethodResult.res
(CTID)
S-MethodResult.cnf
(STID)
WTP Class 2
transaction
Prof. Dr.-Ing. Jochen H. Schiller
www.jochenschiller.de
MC - 2008
10.45
WSP/B over WTP - method invocation
client
S-SAP
initiator
TR-SAP
responder
TR-SAP
server
S-SAP
S-MethodInvoke.req TR-Invoke.req
TR-Invoke.ind S-MethodInvoke.ind
TR-Invoke.res S-MethodInvoke.res
S-MethodInvoke.cnf TR-Invoke.cnf
TR-Result.req S-MethodResult.req
S-MethodResult.ind
TR-Result.ind
S-MethodResult.res
TR-Result.res
TR-Result.cnf S-MethodResult.cnf
Prof. Dr.-Ing. Jochen H. Schiller
www.jochenschiller.de
MC - 2008
10.46
WSP/B over WTP - asynchronous,
unordered requests
client
S-SAP
server
S-SAP
S-MethodInvoke_1.req
S-MethodInvoke_2.req
S-MethodInvoke_2.ind
S-MethodInvoke_1.ind
S-MethodInvoke_3.req
S-MethodResult_1.req
S-MethodInvoke_3.ind
S-MethodResult_1.ind
S-MethodResult_3.req
S-MethodResult_3.ind
S-MethodResult_2.req
S-MethodInvoke_4.req
S-MethodInvoke_4.ind
S-MethodResult_4.req
S-MethodResult_4.ind
S-MethodResult_2.ind
Prof. Dr.-Ing. Jochen H. Schiller
www.jochenschiller.de
MC - 2008
10.47
WSP/B - confirmend/non-confirmed
push
client
S-SAP
S-Push.ind
(PH, PB)
server
S-SAP
S-Push.req
(PH, PB)
WTP Class 0
transaction
client
S-SAP
S-ConfirmedPush.ind
(CPID, PH, PB)
server
S-SAP
S-ConfirmedPush.req
(SPID, PH, PB)
S-ConfirmedPush.res
(CPID)
S-ConfirmedPush.cnf
(SPID)
WTP Class 1
transaction
Prof. Dr.-Ing. Jochen H. Schiller
www.jochenschiller.de
MC - 2008
10.48
WSP/B over WDP
S-Unit-MethodInvoke.req
(SA, CA, TID, M, RU)
client
S-SAP
server
S-SAP
S-Unit-MethodInvoke.ind
(SA, CA, TID, M, RU)
S-Unit-MethodResult.req
(CA, SA, TID, S, RH, RB)
S-Unit-MethodResult.ind
(CA, SA, TID, S, RH, RB)
S-Unit-Push.req
(CA, SA, PID, PH, PB)
S-Unit-Push.ind
(CA, SA, PID, PH, PB)
WDP Unitdata
service
Prof. Dr.-Ing. Jochen H. Schiller
www.jochenschiller.de
MC - 2008
10.49
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
10.50
WAE logical model
Origin Servers
web
server
other content
server
Gateway
response
with
content
encoders
&
decoders
push
content
request
Prof. Dr.-Ing. Jochen H. Schiller
www.jochenschiller.de
Client
encoded
response
with
content
encoded
push
content
encoded
request
MC - 2008
WTA
user agent
WML
user agent
other
WAE
user agents
10.51
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
10.52
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
10.53
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
10.54
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
10.55
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
10.56
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
10.57
WTA logical architecture
other telephone networks
WTA server
client
WML
scripts
WTA & WML
server
mobile
network
WTA
user agent
WAP gateway
repository
WML
decks
WTA
services
network operator
trusted domain
encoders
&
decoders
other
servers
third party
servers
Prof. Dr.-Ing. Jochen H. Schiller
device
specific
functions
firewall
www.jochenschiller.de
MC - 2008
10.58
Voice box example
WTA-User-Agent
WTA-Gateway
WTA-Server
Mobile network
Indicate new voice message
Voice box server
Generate new deck
Service Indication
Display deck;
user selects
WSP Get
Binary WML
Display deck;
user selects
WSP Get
Binary WML
Push URL
HTTP Get
WML
Respond with content
HTTP Get
WML
Respond with card
for call
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 H. Schiller
www.jochenschiller.de
MC - 2008
10.59
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
10.60
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
10.61
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
10.62
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
Push OTA
Protocol
User Agents
Prof. Dr.-Ing. Jochen H. Schiller
Push Proxy
Gateway
Push
Access
Protocol
Server
application
Coding,
checking
www.jochenschiller.de
Push Initiator
MC - 2008
10.63
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
10.64
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
10.65
Examples for WAP protocol stacks
(WAP 1.x)
WAP standardization
WAE user agent
outside WAP
WAE
WSP
transaction based
application
WTP
WTP
WTLS
datagram based
application
WTLS
WTLS
UDP
WDP
UDP
WDP
UDP
WDP
IP
non IP
IP
non IP
IP
non IP
(GPRS, ...) (SMS, ...)
(GPRS, ...) (SMS, ...)
(GPRS, ...) (SMS, ...)
1.
2.
3.
typical WAP
application with
complete protocol
stack
Prof. Dr.-Ing. Jochen H. Schiller
pure data application
with/without
additional security
www.jochenschiller.de
MC - 2008
10.66
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)
mobile terminal
mobile network
cHTML + tags
HTTP(S)
TL
TL
PDC-P
PDC-P
Prof. Dr.-Ing. Jochen H. Schiller
TCP
IP
L2
L1
gateway
TCP
IP
L2
L1
www.jochenschiller.de
TCP
IP
L2
L1
content provider
cHTML + tags
HTTP(S)
TCP
IP
L2
L1
MC - 2008
10.67
Email example: i-mode push with
SMS
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…
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.
Prof. Dr.-Ing. Jochen H. Schiller
www.jochenschiller.de
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 also
UMTS!)
- not successful in e.g.
Germany (stopped in 2008)
MC - 2008
10.68
i-mode protocol stack based on WAP
2.0
user equipment
gateway
server
cHTML
cHTML
HTTP
HTTP
SSL
SSL
WTCP
WTCP
TCP
TCP
IP
IP
IP
IP
L2
L2
L2
L2
L1
L1
L1
L1
i-mode can use WAP 2.0/Internet protocols (example: i-mode in Germany over GSM/GPRS)
Prof. Dr.-Ing. Jochen H. Schiller
www.jochenschiller.de
MC - 2008
10.69
i-mode – technical requirements
Functions
Descriptions
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
Status
MC - 2008
Requirement
10.70
i-mode – very first examples I
Prof. Dr.-Ing. Jochen H. Schiller
www.jochenschiller.de
MC - 2008
10.71
i-mode – very first examples II
Prof. Dr.-Ing. Jochen H. Schiller
www.jochenschiller.de
MC - 2008
10.72
i-mode – very first examples III
Prof. Dr.-Ing. Jochen H. Schiller
www.jochenschiller.de
MC - 2008
10.73
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
10.74
External
services EFI
Crypto
libraries
WAE/WTA User Agent
(WML, XHTMLMP)
Push
Provisioning
Authentication
Identification
Service
Lookup
PKI
Secure
transport
Secure
bearer
Push
OTA
Cookies
Synchronisation
Hypermedia transfer
(WTP+WSP, HTTP)
CSD
IPv6
Prof. Dr.-Ing. Jochen H. Schiller
www.jochenschiller.de
MMS
Connections
(TCP with
wireless profile)
Datagrams
(WDP, UDP)
IPv4
Streaming
Transport
Navigation
Discovery
Capability Negotiation
USSD
SMS
GPRS
FLEX
...
MPAK
MC - 2008
...
Protocol framework
Content
formats
Session
Multimedia Messaging
(Email)
Transfer
Security
services
Bearer
Service
discovery
Application
framework
WAP 2.0 architecture
10.75
WAP 2.0 example protocol stacks
WAP device
WAE
WSP
WTP
WTLS
WDP
bearer
WAP gateway
WSP
WTP
WTLS
WDP
bearer
Web server
WAE
HTTP
HTTP
TLS
TCP
IP
TLS
TCP
IP
WAP 1.x Server/Gateway/Client
WAP device
WAE
HTTP
TLS
TCP‘
IP
WAP proxy
TCP‘
IP
TCP
IP
Web server
WAE
HTTP
TLS
TCP
IP
WAP Proxy with TLS tunneling
Prof. Dr.-Ing. Jochen H. Schiller
www.jochenschiller.de
WAP device
WAE
HTTP‘
TCP‘
IP
WAP proxy
HTTP‘
TCP‘
IP
HTTP
TCP
IP
Web server
WAE
HTTP
TCP
IP
WAP HTTP Proxy with profiled TCP and HTTP
WAP device
WAE
HTTP
TCP
IP
IP router
IP
IP
Web server
WAE
HTTP
TCP
IP
WAP direct access
MC - 2008
10.76
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
10.77
Applications of Java ME
• Example first cellular phones
• NTT DoCoMo introduced ippli
• 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
10.78
Characteristics and architecture
• Java Virtual Machine
• Virtual Hardware (Processor)
• KVM (K Virtual Machine)
Applications
• Min. 128 kByte, typ. 256 kByte
• Optimized for low performance devices
• Might be a co-processor
Profile
(MIDP)
• 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
Configurations
(CDC, CLDC)
Java Virtual Machine
(JVM, KVM)
Operating system
(EPOC, Palm, WinCE)
• Profiles
• Interoperability of heterogeneous devices
belonging to the same category
• MIDP (Mobile Information Device Profile)
Hardware
(SH4, ARM, 68k, ...)
• Defines interfaces for GUIs, HTTP, application
support, … -> MIDlets
Prof. Dr.-Ing. Jochen H. Schiller
www.jochenschiller.de
MC - 2008
10.79
Hardware independent development
Prof. Dr.-Ing. Jochen H. Schiller
www.jochenschiller.de
MC - 2008
10.80
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
10.81
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
Prof. Dr.-Ing. Jochen H. Schiller
www.jochenschiller.de
MC - 2008
10.82