Date post: | 28-Dec-2015 |
Category: |
Documents |
Upload: | garry-hardy |
View: | 227 times |
Download: | 0 times |
Mobile Communications Chapter 10: Support for Mobility
File systems Data bases WWW and Mobility WAP (Wireless Application Protocol), i-mode & Co.
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)
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
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
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 experimental systems exist 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)
mobile client
File systems - Coda I
Coda is the successor of AFS and offers two different types of replication: Server replication and caching on clients.
Coda is transparent extension of client’s cache manager. Applications use cached replicates of files. Coda offers extensive mechanisms for pre-fetching of files while still
connected, called “Hoarding“. While the client is disconnected, applications work on the replicates, called
emulating.
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 working on whole files.
cacheapplication server
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
File systems - Little Work
Only changes in the cache manager of the client More client states to maintain consistency:
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
File systems - further examples
Ficus not a client/server approach optimistic use of replicates, detection of write conflicts, conflict resolution
on directories 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 Three different modes:
Connected: The server handles all access to files. loosely connected: Clients use local replicates, exchange tokens, and
update files via the network. Disconnected: The client uses only local replicates. Writing is only
allowed if the client is token-holder.
File systems - further examples
Rover Relocatable dynamic objects are objects that can be dynamically
loaded into a client computer from a server to reduce client-server communication.
Queued remote procedure calls allow for non-blocking RPCs when a host is disconnected.
Requests and responses are exchanged as soon as a connection is available.
Conflict resolution is done in the server and is application specific.
Mobiware A mobile middleware environment using CORBA and Java.
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
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
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!
WWW example
Request 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
HTTP 1.0 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
HTTP 1.0 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!
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
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
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...
mobile client
browser
integratedenhancement
System support for WWW in a mobile world I
Enhanced browsers Pre-fetching, caching, off-line use e.g. Internet Explorer, Netscape
Additional, accompanying application Pre-fetching, caching, off-line use e.g. original WebWhacker Problem – not transparent, two different
ways of accessing content: Directly to the web server Via the additional application
webserver
mobile client
browseradditionalapplication
webserver
System support for WWW in a mobile world II
Client Proxy acts as server for the browser and as client for the web server. Pre-fetching, caching, off-line use e.g., Caubweb, TeleWeb, Weblicator,
WebWhacker, WebEx, WebMirror
Network Proxy supports a mobile client on the network side. adaptive content transformation
for bad connections, pre-fetching, caching
e.g., TranSend, Digestor
mobile client
browser
networkproxy
webserver
mobile client
browserclientproxy
webserver
System support for WWW in a mobile world III
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
browserclientproxy
webserver
networkproxy
clientproxy
networkproxy
WAP - Wireless Application Protocol
WAP (Wireless Application Protocol) a specification for a set of communication protocols to standardize the way
that wireless devices, such as cellular telephones and radio transceivers, can be used for Internet access, including e-mail, the World Wide Web, newsgroups, and Internet Relay Chat (IRC).
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 developmentsPlatforms
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 + …)
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.
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
WAPThe Wireless Application Environment (WAE) - Application layer
a general-purpose application environment based on a combination of World Wide Web (WWW) and mobile telephony technologies. WAE includes a micro-browser environment containing the following functionalities:
Wireless Markup Language (WML) A lightweight markup language, similar to HTML, but optimized for use in hand-held mobile terminals;
WMLScript A lightweight scripting language, similar to JavaScript
Wireless Telephony Application (WTA) Telephony services and programming interfaces.
Wireless Session Protocol (WSP) - Session layer gives the functionality of HTTP but in a more optimized way.
Wireless Transaction Protocol (WTP) – Session layer runs on top of a datagram service and provides as a light-weight
transaction-oriented protocol. Wireless Transport Layer Security (WTLS) – Transport layer
a security protocol analogous to the industry-standard Transport Layer Security (TLS) protocol, formerly known as Secure Sockets Layer (SSL) in WWW model.
Wireless Datagram Protocol (WDP) – Transport layer The Transport layer protocol in the WAP architecture is referred to as the
Wireless Datagram Protocol (WDP).
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
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)
WDP - Service Primitives
T-SAP T-SAP
T-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)
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 PSTNCircuitPSTN
CircuitSubnetworkSubnetwork
InterworkingFunction
Internet Service ProviderRemote Access Service
PSTNCircuitPSTN
Circuit
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
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
SEC-Unitdata - transferring datagrams
SEC-Unitdata.req(SA, SP, DA, DP, UD) SEC-Unitdata.ind
(SA, SP, DA, DP, UD)
senderSEC-SAP
receiverSEC-SAP
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)
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
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)
WTP Class 0 transaction
TR-Invoke.req(SA, SP, DA, DP, A, UD, C=0, H)
Invoke PDUTR-Invoke.ind(SA, SP, DA, DP, A, UD, C=0, H‘)
initiatorTR-SAP
responderTR-SAP
WTP Class 1 transaction, no user ack & user ack
TR-Invoke.req(SA, SP, DA, DP, A, UD, C=1, H)
Invoke PDUTR-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 PDUTR-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)
WTP Class 2 transaction, no user ack, no hold on
TR-Invoke.req(SA, SP, DA, DP, A, UD, C=2, H)
Invoke PDUTR-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‘)
WTP Class 2 transaction, user ack
TR-Invoke.req(SA, SP, DA, DP, A, UD, C=2, H)
Invoke PDUTR-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‘)
WTP Class 2 transaction, hold on, no user ack
TR-Invoke.req(SA, SP, DA, DP, A, UD, C=2, H)
Invoke PDUTR-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‘)
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
WSP protocols
WSP
Connection mode(uses WTP)
Connectionless mode(uses WDP or WTLS)
• 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)
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
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
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)
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)
WSP/B over WTP - method invocation
S-MethodInvoke.req
S-MethodInvoke.ind
clientS-SAP
serverS-SAP
S-MethodInvoke.res
S-MethodInvoke.cnfS-MethodResult.req
S-MethodResult.ind
S-MethodResult.res
S-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
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.req
S-MethodResult_3.req
S-MethodResult_4.req
S-MethodInvoke_4.ind
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)
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
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, ...
Origin Servers
WAE logical model
webserver
other contentserver
Gateway Client
otherWAE
user agents
WMLuser agent
WTAuser agent
encoders&
decoders
encodedrequest
request
encodedresponsewithcontent
responsewithcontent
pushcontent
encodedpushcontent
Wireless Markup Language (WML)
WML (Wireless Markup Language) is a language that allows the text portions of Web pages to be presented on cellular telephones and personal digital assistants (PDAs) via wireless access.
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
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>
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>
WMLScript
WMLScript is the scripting language used in WML pages .
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
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;
};
Wireless Telephony Application (WTA)
The Wireless Telephony API is an API and framework for accessing telephony and network services.
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");
WTA logical architecture
otherservers
client
repository
WTAuser agent
WAP gateway
encoders&
decoders
other telephone networks
WTA server
WTA & WMLserver
WMLscripts
WMLdecks
WTAservices
mobilenetwork
firewallthird party
servers
network operatortrusted domain
devicespecific
functions
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 Get
Respond with cardfor callWMLBinary WML
Wait for call
Setup call
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>
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");
}
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>
WAP push architecture with proxy gateway
Push Access Protocol Content transmission between server and PPG (Push Proxy Gateway) 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
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="2002-10-30T17:45:32Z"
si-expires="2000-10-30T17:50:31Z">
Salad special: The 5 minute offer
</indication>
</si>
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>
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
1. 2. 3.
i-mode – first of all a business model!
i-mode is a proprietary packet-based information service for mobile phones by NTT DoCoMo.
Access to Internet services in Japan provided by NTT DoCoMo Services
Email, short messages, web, picture exchange, horoscope, ... Big success – more than 30 million users
Many use i-mode as PC replacement For many this is the first Internet contact Very simple to use, convenient
Technology 9.6 kbit/s (enhancements with 28.8 kbit/s), packet oriented (PDC-P) Compact HTML (cHTML) 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
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 also UMTS!)
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
i-mode – technical requirements
Functions 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
i-mode examples I
i-mode examples II
i-mode examples III
WAP 2.0 (July 2001)
WAP 2.0 supports: XHTML with a mobile profile (XHTMLMP) TCP with „Wireless Profile“ HTTP
WAP 2.0 framework consists of: Bearer networks: GPRS Transport services: TCP, WDP or UDP Transfer services: HTTP, Multi-media messaging Service (MMS) Session services: push OTA (Over The Air)
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
WAP 2.0 architecture
Servicediscovery
Securityservices
App
lica
tion
fram
ewo
rkP
roto
col f
ram
ewo
rk
External services EFI
Provisioning
NavigationDiscovery
ServiceLookup
Cryptolibraries
Authenti-cation
Identification
PKI
Securetransport
Securebearer
Se
ssio
nT
ran
sfe
rT
ran
spo
rtB
ea
rer
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
Synchronisation Cookies
WAP 2.0 example protocol stacks
bearerWDPWTLSWTPWSPWAE
WAP device
bearerWDPWTLSWTPWSP
IPTCPTLS
HTTP
IPTCPTLS
HTTP
WAE
Web 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
WAE
Web serverWAP proxy
WAP HTTP Proxy with profiled TCP and HTTP
HTTP‘ HTTP HTTP
IPTCP
HTTPWAE
WAP device
IP IP IPTCP
WAE
Web server
IP router
WAP direct access
HTTP
Java 2 Platform Micro Edition
„Java-Boom expected“ (?) Desktop: over 90% standard PC architecture, Intel x86 compatible, typically
MS Windows systems Do really many people care about platform independent applications?
BUT: Heterogeneous, “small“ devices Internet appliances, cellular phones, embedded control, car radios, ... Technical necessities (temperature range, form factor, power consumption,
…) and economic reasons result in different hardware
J2ME Provides a uniform platform Restricted functionality compared to standard java platform (JVM)
Applications of J2ME
Example cellular phones NTT DoCoMo introduced ippli 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
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, …
Hardware(SH4, ARM, 68k, ...)
Java Virtual Machine(JVM, KVM)
Operating system(EPOC, Palm, WinCE)
Configurations(CDC, CLDC)
Profile(MIDP)
Applications
Hardware independent development
Summary J2ME
Idea is more than WAP 1.x or i-mode Full applications on mobile phones, not only a
browser Includes system updates, end-to-end encryption
Platform independent via virtualization As long as certain common interfaces are used Not valid for hardware specific functions
Limited functionality compared to JVM Thus, maybe an intermediate solution only – until
embedded systems, mobile phones are as powerful as today’s desktop systems