Traversing NAT (Network Address Translation) is one of the issues that hinder SIP communications. Some background about the problem: With an ideal Internet, all devices would be able to communicate end to end without any intermediaries except routers. This assumes each device has a routable IP address, a public reachable Internet identity. In reality, today many of the devices connected on the Internet are using a NAT function present in the border router. While this stops the Internet to initiate connections to the device (bad for IP telephony or other forms of peer-to-peer communications), it also protects the users against malicious attacks. Using NAT, one may also connect multiple devices to the Internet by only using one public IP address. So NAT has both advantages and disadvantages.

It was for me an interesting an utterly refreshing experience to sit face to face with the inventors of SIP and to learn of its extensions to many applications beyond Voice over IP such as presence, mobility and emergency services. On the panel were present also mobile and fixed line service providers as well as technology vendors.

Published by ETSI 

 

ENUM, a convergence tool for translating telephone numbers into Internet addresses used by IP telephony and next generation mobile networks like UMTS, is a key ingredient for the transition to the Next Generation Networks.

Easy service creation is one of the highlights of the SIP protocol. It promises a low cost, quick development cycle for applications around SIP. With so much theory on paper and more than two years of live deployments, what can SIP offer today in terms of classic telephony features and value added services?