A Distributed Proxy Server for Wireless Mobile Web Service Kisup Kim, Hyukjoon Lee, and Kwangsue Chung Information Network 2001, 15 th Conference.

Outline Introduction Distributed proxy server system Proxy server handoff protocol Implementation and performance Conclusion

Introduction Transcoding proxy servers have been widely accepted as a practical means of reducing the delay in wireless Web access. Main functions: caching, transcoding, distillation,and compression. One of the significant drawbacks ： it may become a single point of failure or a bottleneck.

Introduction(Cont.) Multiple proxy servers. Serving mobile hosts within assigned regions. A new handoff(HO) message protocol is proposed to enable handoffs between proxies as the mobile hosts move between regions. Proxy servers synchronization of distilled data.

Distributed proxy server system Service area

Distributed proxy server system When a MH moves to the service area of another proxy,the handoff takes place between two cells served by two proxies. Handoff between the two proxies must be performed. Proxy server handoff message protocol. Past proxy and current proxy. Release the connection to the past proxy and establish new connection to the current one.

Distributed proxy server system

The distributed proxy server is built on top of a standard Web proxy server by adding the modules for handling transcoding and proxy handoff. Message handler Distilled data handler File list manager HTTP handler

Client agent The handoff processing module within client agent consists of : Location information manager Proxy server connection manager Handoff request message generator File handler

Proxy server handoff protocol Proxy server handoff processing ： proxy handoff initiation. Distilled data synchronization between proxies. Handoff between proxy and the Web server. Proxy handoff initiation: MH establishes a new TCP connection to the current proxy. Then issues a handoff request message.

Proxy server handoff protocol The current proxy server may request the past proxy to transfer some distilled files instead of sending the HTTP request to the origin server. Distilled data synchronization. The current proxy server stores these distilled data in cache and transfers them to the MH in the mean time. It helps reduce the delay incurred by fetch of data from the origin server and repeated distillation.

Proxy server handoff protocol Message Format –The handoff request message between the current proxy and the client agent. –The message for the distilled data synchronization step between current and past proxy server.

Proxy server handoff protocol –Total size: total length of handoff request message –Past proxy IP: past proxy IP address. –User Request: HTTP request message. –List of files received at MH –Received bytes –In case the connection between the past proxy and the MH was broken in the middle of transferring an file,the transfer must be resumed by the current proxy.

Proxy server handoff protocol –Distilled data request message

Proxy server handoff protocol –Distilled data message –It is the response message to the distilled data request message.

Implementation and performance The proxy server is based on a usual HTTP proxy and implemented on the UNIX environment. Mobile hosts uses Win98 and Win CE. The HTTP requests from client browser are processed in the multithread manner by the client agent. Test-bed: –Handoff between cells was emulated by the proxy handoff trigger with generates HO event signal.

Implementation and performance

The response time of web pages in the single proxy server system was 1.25 times slower than that of the distributed proxy server.

Conclusion Distributed proxy server system is used to solve the bottleneck problem of proxy server. This paper designed the distributed proxy server and the proxy server handoff message protocol for this purpose.