The Research Of IP Telephone Based On SIP

The origin of IP telephone goes back to the development of IP network and the voice transmission experiments with package networks. Comparing to the traditional telephone, IP telephone has great advantages over price, user requirement and multimedia session. No doubt, all these will revolutionize telephone networks and service.There are two more authoritative group pursuing in the research on IP telephone, that is, ITU-T and IETF. So this leads to two signaling standards of IP telephone, viz. H.323 and SIP. SIP , a text-based protocol, is easier to implement and has stronger function than H.323 based on binary code. Moreover, next generation network focuses on the Softswitch, and SIP may become the signaling protocol between Softswitch equipments. Therefore, the research of SIP is very significant. More and more people are attractive in SIP for its new revision of 2002. So this paper bases on all these and discusses the IP telephone on SIP.The thesis is mainly concerns about:(1) This paper discusses the protocol stack of voice over IP. The function, address format, the mode of call request and response, SIP module and correlative protocol are introduced.(2) The communication flow and network topology are deeply analyzed. The realizability of number portability and the all-one-number are discussed.(3) IP and H.323 are compared in terms of the function, simplicity, flexibility, third party call control and security.(4) The VoIP-SIP network topology model is described according to security and QoS.(5) The chat software is partly completed according to the communication mode of SIP through programming on user proxy and SIP server.Although the use of H.323 has more advantages than that of SIP currently, and there are hardly any SIP instances, SIP has good future. This paper has only finished some elementary work, so there is more work to do in the future.