Browse Prior Art Database

SMART POLL ALGORITHM

IP.com Disclosure Number: IPCOM000008003D
Original Publication Date: 1997-Mar-01
Included in the Prior Art Database: 2002-May-10
Document File: 3 page(s) / 183K

Publishing Venue

Motorola

Related People

Gerald K. lllner: AUTHOR

Abstract

The implementation of client-server based sys- tems in computer and communications networks introduces many interesting and challenging prob- lems. In client-server based systems, information on the server site may change very frequently. This poses a problem of maintaining information consis- tency between the client and the server on a "near real time" basis. As a result there is a need for a client-server interface technique which minimizes server site activities while providing information updates to clients within a guaranteed propagation delay time period.

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@ MOTOROLA Technical Developments

SMART POLL ALGORITHM

by Gerald K. lllner

1.0 INTRODUCTION

  The implementation of client-server based sys- tems in computer and communications networks introduces many interesting and challenging prob- lems. In client-server based systems, information on the server site may change very frequently. This poses a problem of maintaining information consis- tency between the client and the server on a "near real time" basis. As a result there is a need for a client-server interface technique which minimizes server site activities while providing information updates to clients within a guaranteed propagation delay time period.

To address this problem two basic client-server interface techniques are commonly employed:

  Asynchronous Notification: Utilizing this technique, the server notifies the client or clients immediately whenever an information change occurs. Each change event triggers one notification activity for each client. The resulting activity at the server site is directly related to the server's informa- tion change rate and to the number of clients sup- ported. During time periods when there is no change to the server site information no activity is conducted on the server. However, during time peri- ods when there is a high change rate the triggered server activity to propagate each information change to each client is substantial.

  Polling: Utilizing this technique the clients periodically poll the server to acquire all informa- tion changes that have occurred since the previous poll request. The polling interval is mandated by an acceptable client propagation delay of server infor- mation changes. As a result there is a constant serv- er site activity load which is directly related to the polling interval and to the number of clients. The server site activity load is, however, independent of the server's information change rate. During time

periods when the change rate on the server is higher than the propagation delay the server activities to satisfy client information updates are optimized; however, during time periods when there is a low change rate on the server, the periodic poll requests from clients trigger unnecessary serve* activity.

  In a system with a lot of clients and an event pattern characterized by long pauses in change followed by sudden bursts of information change, a "hybrid" algorithm is needed which combines the strengths of Asynchronous Notification and Polling. The Smart Poll Algorithm is a hybrid of such techniques.

2.0 THE SMART POLL ALGORITHM-DESCRIPTION

  The Smart Poll algorithm improves polling dur- ing periods of idle time (no server change events) and during periods of busy time (server change events).

2.1 IDLE TIME:

  Instead of each client continuously polling the server for information change, a new dedicated client called Polling Hint interrogates the server site for information changes on behalf of the clients.

  When the polling response indicates a change to the...