Transcript Support for Mobility

Mobile Communications
Chapter 10: Support for Mobility
•
•
•
•
File systems
Data bases
WWW and Mobility
WAP (Wireless Application Protocol), i-mode & Co.
10.1
Mobile, bearable multimedia
equipment …
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)
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
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
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)
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
– ifmobile
different
users have changed the same file a manual
client
reintegration of the file into the system is necessary
applicationapproach,
cache
server
– optimistic
coarse grained (file size)
10.7
•
Hoarding
File systems• -States
Coda
II
of a client
– 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
•
hoarding
disconnection
weak
connection
write
disconnected
connection
Cache misses
– modeling of user patience: how long
can a user wait for data without an error
message?
– function of file size and bandwidth
strong
connection
disconnection
emulating
10.8
File systems - Little Work
• Only changes in the cache manager of the
Connected Partially
Fetch only
Disconnected
Connected
client
Method
normal
delayed write
optimistic
abort at cache
to the server
replication of files miss
• Connection
modes
and use
Network
continuous
continuous
connection on
none
requirements high
bandwidth
bandwidth
Application
office, WLAN packet radio
demand
cellular systems
(e.g., GSM) with
costs per call
independent
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
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
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!
10.12
WWW example
Request to port 80:
or:
GET / HTTP/1.0
GET / HTTP/1.1
Host: www.inf.fu-berlin.de
non persistent
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
<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.fuberlin.de/styles/homepage.css">
<!--script language="JavaScript" src="fuinf.js"-->
<!--/script-->
</head>
<body onResize="self.location.reload();">
...
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
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!
10.15
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 touchpads, 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
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
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...
10.18
System support for WWW in a mobile
world I (some historical)
mobile client
• Enhanced browsers
integrated
enhancement
browser
– Pre-fetching, caching, off-line use
– e.g. Internet Explorer
web
server
mobile client
browser
• Additional, accompanying application
– Pre-fetching, caching, off-line use
– e.g. original WebWhacker
additional
application
web
server
10.19
System support for WWW in a mobile
world II (some historical)
mobile client
• Client Proxy
– Pre-fetching, caching, off-line use
– e.g., Caubweb, TeleWeb, Weblicator,
WebWhacker, WebEx, WebMirror,
...
browser
client
proxy
web
server
mobile client
• Network Proxy
– adaptive content transformation
for bad connections, pre-fetching,
caching
– e.g., TranSend, Digestor
browser
network
proxy
web
server
10.20
System support for WWW in a mobile
world III (some historical)
mobile client
• 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
browser
client
proxy
web
server
network
proxy
mobile client
browser
client
proxy
web
server
network
proxy
– “channels”, content negotiation, ...
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 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 + …)
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.
10.23
WAP 1.x - reference model and
protocols
Internet
HTML, Java
A-SAP
WAP
Application Layer (WAE)
S-SAP
additional services
and applications
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.
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
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)
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)
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
Interworking
Function
CSD-RF
PSTN
Circuit
IP
PPP
PSTN
Circuit
Subnetwork
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
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
10.30
SEC-Unitdata - transferring datagrams
sender
SEC-SAP
SEC-Unitdata.req
(SA, SP, DA, DP, UD)
receiver
SEC-SAP
SEC-Unitdata.ind
(SA, SP, DA, DP, UD)
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)
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
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)
10.34
WTP Class 0 transaction
initiator
TR-SAP
TR-Invoke.req
(SA, SP, DA, DP, A, UD, C=0, H)
responder
TR-SAP
TR-Invoke.ind
(SA, SP, DA, DP, A, UD, C=0, H‘)
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.cnf
(H)
responder
TR-SAP
TR-Invoke.ind
(SA, SP, DA, DP, A, UD, C=1, H‘)
TR-Invoke.res
(H‘)
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)
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)
TR-Result.cnf
(H‘)
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.cnf
(H)
TR-Result.ind
(UD*, H)
TR-Result.res
(H)
responder
TR-SAP
TR-Invoke.ind
(SA, SP, DA, DP, A, UD, C=2, H‘)
TR-Invoke.res
(H‘)
TR-Result.req
(UD*, H‘)
TR-Result.cnf
(H‘)
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)
TR-Result.cnf
(H‘)
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
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)
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
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
10.43
WSP/B session termination
client
S-SAP
server
S-SAP
S-Disconnect.req
(R)
S-Disconnect.ind
(R)
S-Disconnect.ind
(R)
WTP Class 0
transaction
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
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
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.ind
S-MethodResult_3.ind
S-MethodResult_1.req
S-MethodInvoke_3.ind
S-MethodResult_3.req
S-MethodResult_2.req
S-MethodInvoke_4.req
S-MethodInvoke_4.ind
S-MethodResult_4.ind
S-MethodResult_4.req
S-MethodResult_2.ind
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
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
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, ...
10.50
WAE logical model
Origin Servers
web
server
other content
server
Gateway
response
with
content
push
content
request
encoders
&
decoders
Client
encoded
response
with
content
encoded
push
content
encoded
request
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
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>
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>
10.54
</wml>
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
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;
};
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
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
third party
servers
encoders
&
decoders
other
servers
device
specific
functions
firewall
10.58
WTA-User-Agent
Voice box example
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
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>
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");
}
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>
10.62
WAP push architecture with proxy
gateway
• Push Access Protocol
– Content transmission between server and PPG
– First version uses HTTP
• Push OTA (Over ThePush
Air)
Protocol
Push
Proxy
OTA
–Client
Simple,Push
optimized
Protocol
– Mapped onto WSP
User Agents
Gateway
Coding,
checking
Access
Protocol
Push Initiator
Server
application
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">
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
10.65
.dtd">
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
pure data application
with/without
additional security
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)
mobile•terminal
mobile
gateway
content
provider ARQ, push,
Compact HTML
plusnetwork
proprietary tags,
special transport
layer (Stop/go,
oriented)
cHTML +connection
tags
cHTML + tags
HTTP(S)
TL
TL
PDC-P
PDC-P
TCP
IP
L2
L1
TCP
IP
L2
L1
TCP
IP
L2
L1
HTTP(S)
TCP
IP
L2
L1
10.67
Email example: i-mode push with
SMS
application
WSP
WTP
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…
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.
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)
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)
10.69
Functions
i-mode – technical
requirements
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
10.70
i-mode – very first examples I
10.71
i-mode – very first examples II
10.72
i-mode – very first examples III
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
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
MMS
Connections
(TCP with
wireless profile)
Datagrams
(WDP, UDP)
IPv4
Streaming
Transport
Navigation
Discovery
Capability Negotiation
USSD
SMS
GPRS
FLEX
MPAK
...
...
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
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
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)
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
10.78
•
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
Applications
Profile
(MIDP)
Configurations
(CDC, CLDC)
Java Virtual Machine
(JVM, KVM)
Operating system
(EPOC, Palm, WinCE)
Hardware
(SH4, ARM, 68k, ...)
10.79
Hardware independent
development
10.80
Summary Java ME
• Idea is more than WAP 1.x or imode
– Full applications on mobile phones,
not only a browser
– Includes system updates, end-toend encryption
• Platform independent via
virtualization
– As long as certain common
interfaces are used
– Not valid for hardware specific
functions
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
10.82