Support For Mobility

World wide web

● Problems encounters the web applications used in a mobile and wireless environment.

● Basic intro about HTTP– It is a stateless , lightweight , application level

protocol for data transfer between servers and clients.

– HTTP transaction consists of HTTP request issued by the client and and HTTP response from a server

HTTP

● It supported only simple caching mechanisms to avoid unnecessary retransmission.

● Caches may be located anywhere between server and client.

● Each client maintains a cache locally to minimize delay when jumping back and forth on web page.

● Application must not cache page beyond expiration.

HTTP problems

● Bandwidth and delay

– It is designed with high bandwidth/low delay connections in mind.

– HTTP header is quite large and redundant.

– Server transfer content uncompressed.

– TCP connection is used for each item on web page, huge overhead with each item.(three way handshack and four way disconnection)

– Requires an additional request for DNS.

HTTP problems

● Caching – It is usefull in many cases, often disabled by content

provider (number of clicks on a page).

– Present-day pages contain dynamic objects that cannot be cached.

– Page often created dynamically depending on the type of browser,client harware,client location etc.

– Can't merge static content with dynamic remainder page.

HTML

● It is designed for standard desktop computers connected witht a fixed wire.

● Having high-resolution, mouse,sound system and large hard disk.

● Wireless devices having low-resolution, limited user interference, low performance CPUs

● Pages are degined for nice presentation of content, not for efficient transfer of this content.

HTTP and HTML solutions

● Image scaling

– Scale down to fewer colors, lower resolution or just title of picture. User decide to zoom or download.

● Content transformtion

– Many application documents availabe is certain format (pdf, post script etc.)

– Convert and transfer.● Content extraction/semantic compression -

– Headline or keyword extracted from a document

HTTP and HTML solutions

● Special language and protocols

– Replace HTML

– Like introduction of Handheld Device Transport Protocol (HDTP) and the Handheld Device Markup Language (HDML)

● Push technologies

– Instead of pulling content from server , the server could push content to a client.

– Avoid overhead of connection on each object

System Architecture● Integrated browser enhancement

– Integration of caching into web browser.

– Does't perform pre-fatching of pages but stores already transferred contents.

● Additional application support browsing

– Pre-fatching of content, caching and disconnected service

● Client proxy as browser support

– Browser access the web server through the client proxy.

– Proxy can perform pre-fetch and cache content.

System Architecture● Network proxy as browser support

– proxy support mobile client on the network side

– Further enhancement using I-TCP.

● Client and network proxy as browser support

– Combined client and n/w proxy

● Client and nerwork proxy with special transmission protocol

– Client , n/w proxy with special transmission protocol

Wireless Application Protocol(version 1.x)

● WAP Forum was founded in June 1997 by Ericsson, Motorola, Nokia and Unwired Planet

● In 2002, the WAP forum together with open mobile architecture forum formed open mobile alliance.

● Objective – To bring diverse internet content and other data services to digital cellular phones and other wireless, mobile terminals

Design Consideration

● Interoperable – alowing terminals and s/w from different vendors to communicate with n/w from different providers.

● Scaleable – should scale with customers needs and number of customers

● Efficient – provision of QoS suited to the wirless and mobile n/w

● Reliable● Secure

Architecture