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A NAT Proxy Server for an Internet Telephony Service  

손주영 (한국해양대학교 컴퓨터공학과)
Publication Information
Journal of KIISE:Computing Practices and Letters / v.9, no.1, 2003 , pp. 47-59 More about this Journal
Abstract
The Internet telephony service is one of the commercially successful Internet application services. VoIP technology makes the service come true. VoIP deploys H.323 or SIP as the standard protocol for the distributed multimedia services over the Internet in which QoS is not guaranteed. VoIP carries the packetized voice over the RTP/UDP/IP protocol stack. The data transmission trouble is caused by UDP when the service is provided in private networks and some ISP-provided Internet access networks in the private address space. The Internet telephony users in such networks cannot listen the voices of the other parties in the public Internet or PSTN. Making the problem more difficult, the Internet telephony service considered in this paper gets the incoming voice packets of every session through only one UDP port number. In this paper, three schemes including the terminal proxy, the gateway proxy, and the protocol translation are suggested to solve the problems. The design and implementation of the NAT proxy server based on gateway proxy scheme are described in detail.
Keywords
VoIP; Internet telephony service; VoIP; NAT problem; Proxy server;
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