Zoiper

Zoiper is an IP telephony client that supports IAX and SIP protocols.

IAX2 - Inter-Asterisk eXchange protocol - VoIP data exchange protocol between IP-PBX Asterisk. It is best suited for NAT network address translation, unlike SIP and H.323, uses only one port 4569 of UDP for signaling and media streaming, while the latter uses different ports for this purpose.

SIP (Session Initiation Protocol) - is a data communication protocol that describes the way in which a user's Internet session, including the exchange of multimedia content (video and audio conferences, instant messages, online games), is established and ended.

Program features

• support for T.38 faxes;
• support for Session Traversal Utilities for NAT to identify subscribers with NAT;
• support for different audio codecs;
• different user accounts;
• buffer for "smoothing" momentary connection interruptions;
• echo cancellation.