As the number of Internet users increases rapidly, IPv4 address shortage has been developing.The shortage can be completely solved by using IPv6, but it takes too much time to replace all the equipments in the world.Therefore, NAT is used as a temporally solution. NAT reduces the use of address by connecting a local address to a public address only when it is necessary, which can be a good solution for server-client models, but causes NAT-Traversal problem in peer-to-peer communication such as VoIP using SIP in NAT environment. STUN and TURN are used to solve NAT-Traversal problem.This document explains how STUN and TURN are applied to SIP to solve problems when using NAT and points out problems that STUN and TURN cause, and suggests a way to improve.
The wireless cellular networks have evolved from IS-95A/B to cdma2000 1X, EV-DO, and WCDMA to improve data service quality. A carries also preserve in their efforts to rev up wireless data service. Despite this efforts, call setup latency has occurred on cdma2000 1X and EV-DO systems. It is an impediment to data service activation. In measuring the real delay time during call establishment from MS to BSC, PCF and PDSN, it is found out that point-to-point protocol between MS and PDSN is major source of delay. Therefore, a simplified PPP is proposed, considering the difference in transmission speed of links among nodes. Then the inter-working scenarios between MS and PDSN is presented with simplified PPP and/or legacy PPP, and the proposed scheme is verified with superior performance over legacy PPP, through comparing the number of packets required for data call setup.
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