A Cost-efficient Approach: Putting SIP, NAT,and Mobile IP All Together

Abstract

Voice over IP (VoIP) is a attractive alternation of traditional circuit-switched telephony for lower cost on operating and equipments, and advantages provided by IP. Internet Protocol version 4 (IPv4) is the most popular network layer protocol in current Internet. However, the 32-bits IPv4 address space is insucient, and IP mobility support for IPv4 is poor. Internet Protocol version 6 (IPv6) xes both the problems of IPv4, but the cost of new equipments is high. Network Address Translator (NAT) is a temporary way to solve the problem of insucient address space before the popularity of IPv6, though the problem of IP mobility is still not concerned. Session Initiation Protocol (SIP) is widely used in internet telephony, but SIP does not consider the use of NAT. In this work, we propose a Voice over IPv4 solution by using NAT, and IP mobility is also concerned. An Application Layer Gateway is included to solve additional problems in the proposed architecture. The feasibility of our solution is proved by phyical implementation, and the delay of voice is also insignicant.