VoIP protocols


In a public network environment, products from different companies must be able operate with each other if Voice over IP to make it easy to use for end users. To achieve interoperability, standards are being developed and currently the most common standard for VOIP is the H.323 standard.
  • open H323.org - The OpenH323 project aims to create a full featured, interoperable, Open Source implementation of the ITU H.323 teleconferencing protocol that can be used by personal developers and commercial users without charge.
  • isdn2h323 - Project homepage for isdn2h323, a Linux-based ISDN to H.323 gateway.
  • NAT H323 under Linux - Mini-HOWTO for NAT & H.323 - configuring Linux to support H.323 while using network address translation.
  • Asterisk - Open Source telephony switching and private branch exchange (PBX) daemon. Supported signalling protocols: H.323.


Session Initiation Protocol
  • SIP - FAQs, background materials and lists of current work in this field.
  • SIP Forum - A membership based forum. Also contains a news board.
  • SIP Center - Portal with technical and market resources aimed at commercial developers. Also provides a testbed area for software and proxy development.


SCCP provides connectionless and connection-oriented network services above MTP Level 3. While MTP Level 3 provides point codes to allow messages to be addressed to specific signaling points, SCCP provides subsystem numbers to allow messages to be addressed to specific applications (called subsystems) at these signaling points. SCCP is used as the transport layer for TCAP-based services such as freephone (800/888), calling card, local number portability, wireless roaming, and personal communications services (PCS). Global Title Translation