PortaOne/PortaSIP has a very bad implementation of NAT traversal. Most of the time the NAT type at the user end is not identified properly and the rtp media streams are obligatorily routed through the SIP server. This causes a useless load of the SIP server and unnecessary delays in VOIP communication. Be careful: the after-sale service of Portaone is not the same as the before-sale publicity. Once we published a comparison of various sip/billing solutions. Portaone was one of the best in the list. According to the feedbacks we have from the current customers of Portaobe, the company currently have many problems catching up the technology and providing proper support of already sold systems.