Enterprise-class Ip Telephony System To Achieve The Research

Compared with traditional telephone , IP telephone is getting more attention for its effective use of network bandwidth, low-cost and provision of diverse add-in services easily.Recently,IP telephone tech ( VoIP-Voice over IP ) has made further progresses and improvement,Now there are two major protocol stacks, H.323 protocol stacks put forward by ITU-T and SIP-based telephone tech by IETF. In order to obtain precise information beneficial to company very quickly and improve the employee's efficiency, company needs lots of communication and has to spend much money on it ,so many companies need IP telephone system that is low-cost and can provide colorful servives.This article try to study and design IP telephone system suitable to these companies. H.323 can make the intercommunication between IP and telephone network more easily than SIP for its signalling mode refers to existing telephone system. So the designed IP telephone system is based on H.323 protocol stacks.First This article discusses the basic theory of IP telephone ,then it analyzes structure of H.323 system, at last offers the architecture of software modules of H.323 system. It consists of four parts: (1) Introduction:it contains chapter 1,Chapter 1 reviews the background, foreground and the intention of this article.(2) Theory and Techs: it contains chapters from 2 to 3.Chapter 2 describes theory of IP telephone, typical applications,key techs and low-layer network techs used by IP telephone;Chapter 3 discusses the structure of H.323 system and design and application of vital part--gateway. (2)Design and implementation: it contains chapters from 4 to 7.Chapter 4 introduces the top structure of H.323 software modules and gives important classes of system entities; Chapter 5 to chapter 7 analyze modules of H.225 RAS,H.255 call,H.245 ,then gives their flowchart , graphs of typical program and important data structures. (3)Experiments: it contains chapter 8 which offers the experiments to test and validate the designed H.323 system .The software code is written and tested in Visual C++ environment,the experimental mode of IP telephone system has been validated.