mobile packet services: worldwide wireless web(4w)old.hsn.or.kr/workshop/hsn2001/data/lks.pdf ·...

Computer Comunications & Mobile Computing Lab.

Mobile Packet Services:Mobile Packet Services:Worldwide Wireless Web(4W)Worldwide Wireless Web(4W)

20012001년년 22월월 1515일일

임임 경경 식식

kslimkslim@@knuknu.ac..ac.krkr

Kyungshik Lim HSN2001HSN20012

CCMC Lab.KYUNGPOOK NATIONAL UNIVERSITY

WirelessWWW Access

Mobile Packet Services:WWWW

IP PIPE

HTTP PIPE

MobilityTransparency

XML-basedWWW Contents

Mobile Web Computing Models

QoS Optimization

Wireless &Wired Home

Networks

Internet

HomeGateways

WirelessGateways

Cellular Network

Mobile Routers/Gateways

Packet Data Network

Mobile Packet DataNetwork

Wireless Lan



Presentation Outline

QoS in Mobile Packet Networks

Optimizing TCP/IP for Mobile Networks

QoS Driven, High-level Communication Protocols

QoS Driven, Full Protocol Stacks

Wireless Access to the WWW

Dynamic Documents

Dynamic URLs

Mobile Browser (MOWSER)

WebExpress



Presentation Outline

Mobile Web Computing Models

Client/Server Model

Client/Proxy/Server Model

Disconnected Operation Model

Mobile Agent Model

Thin Client Model

Case Study

Q & A



Optimizing TCP/IP for Mobile Networks (1)

Ideal TCP behaviorSender should simply retransmit a packet lost due to transmission errors, without taking any congestion control actionsTransmission errors should be hidden from the sender

Various schemesLink-layer retransmissionsSplit connection approachTCP-aware link layerTCP-unaware approximation of TCP-aware link layerExplicit notification, etc.




Link Layer Retransmission

application

transport

network

link

physical

application

transport

network

link

physical

application

transport

network

link

physical

TCP connection

FH BS MH

retrans




Split Connection Approach

application

transport

network

link

physical

application

transport

network

link

physical

application

transport

network

link

physical

TCP connection

FH BS MH

TCP connection

retrans



QoS Driven, High-level Communication Protocols

Optimizing the behavior and performance of transport protocols is not sufficient to maintain the QoS required by applications.

Need application-aware (or application-specific) mechanisms to monitor, request, and maintain QoS in the session and/or application layer protocols

The Loss Profile Approach

QEX: The QoS driven Remote Execution Protocol



QoS Driven, Full Proto Stacks (1)

All layers are aware of either QoS or the limitations introduced by mobility and by the wireless network.

Need wireless and mobile aware full protocol stack to cope with the heterogeneity of networks and mobile platforms for mobile application portability

BARWAN: The Wireless Overlay Network Architecture

WAP: Wireless Application Protocol

MNCRF: Mobile Network Computer Reference Profile




Overlay Networks

Inter-Network RoamingSeamless end-to-end Service

Satellite

Global

Suburban Urban

In- Building

Pico-Cell

Micro-Cell

Macro-Cell

Audio/visual Terminals

Home-Cell

IMT-2000

GII

MobileBroadbandNetwork

Mobility Multimedia

Next Generation Internet

GMPCS




Wireless Application Protocol

WAPClient

IP

WAPGateway

IP

WAP/WebServer

HTTP

TCP

MicroBrowser

TCP

HTTP

IP

?WML Compiler?Image Translator?HTML Filter, etc.

WSP Server

WTP Server

WDP/UDP

IP

RequestResponse

CGI, etc.

WML/HTMLContents

WAPClient

IP

WAPGateway

IP

WAP/WebServer

HTTP

TCP

인터넷인터넷인터넷

MicroBrowser

WSP Client

WTP Client

WDP/UDP TCP

HTTP

IP

•WML Compiler•Image Translator•HTML Filter, etc.

WSP Server

WTP Server

WDP/UDP

IP

Request/ResponseRequest

ResponseCGI, etc.

WML/HTMLContents

Encoded

Bearers :GSM, CDMA...



Wireless Access to the WWW (1)

Most solutions used a Web proxy that enabled Web browsing applications to function over wireless links without imposing changes on browsers and servers.

Prefetch and cache Web pages to the mobile client’s machine

Compress and transform image pages for transmission over low-bandwidth links

Support disconnected and asynchronous browsing operations

Dynamic Documents, Dynamic URLs, Mobile

Browser (MOWSER), WebExpress



Wireless Access to the WWW (2)

WebExpress

Web Browser

Web Express ClientSide Intercept (CSI)

HTTP

(TCP/IP)

Web Server(or Proxy Server)

Web Express ServerSide Intercept (SSI)TCP/IP Connection

HTTP (TCP/IP)

Mobile Hosts Fixed Network



The Client/Server Model

Full client on mobile host and full server on fixed

network (SLIP/PPP C/S)

Client and Server are not mobility-aware

Client caching does not work as the client can be

disconnected when the server invalidates the

cache

Not reliable and of unpredictable performance

Requires special cache invalidation algorithms to

enable caching despite long client disconnections



The Client/Proxy/Server Model

Adding mobility-awareness between the client and

the server. Client and server are not mobility-aware

Proxy functions as a client to the fixed network

server, and as a mobility-aware server to the

mobile client

Proxy may be placed in the mobile host (Coda’s

Venus), or the fixed network, or both (WebExpress)

Application- and user-dependent

One advantage: enables this client design for

resource-poor mobile computers



The Disconnected Operation Model

Approach ⅠProvide full client and a thin version of the server on the mobile platform. In addition, needed data is replicated into the mobile platform. Upon reconnection, updated replicas are synchronized with the home server. Conflict resolution strategies are needed (Coda/Venus & Oracle Lite)

Approach ⅡProvide a full client and a mobility agent that intercepts requests to the unreachable server, emulates the server, buffers the requests, and transmit them upon reconnection (Oracle Mobile Agents)



The Mobile Agent Model

Mobile agent programmed with platform limitations and user profile receives a request; moves into the fixed network near the requested service

Mobile agent acts as a client to the server, or invokes a client to the server

Based on the nature of the results, experienced communication delays, and programmed knowledge, the mobile agent performs transformations and filtering

Mobile agent returns back to mobile platform, when the client is connected



The Thin Client Model

Thin client fits in resource poor info appliances

Bounded communication

Requires at least weak connection

CITRIX WinFrame and ICA thin client

InfoPad

ThinClient

ServerKeyboard and mouse events

Display events



WAP

WMLWMLScript

WSP

WTLS

UDP

WTP

HTMLJavaScript

HTTP

TCP

TLS - SSL

IP

HTTPU/MU

UDP TCP

GENA SSDP

SOAP

HTTPGENA

HTTP

UPnP vendorUPnP Forum

XML Description

WEB UPnP

CASE STUDY : WAP+WEB+UPnP