Skinny Client Control Protocol (SCCP)

In the present scenario when Telephony systems are moving to a common wiring plant the end station of a LAN or IP- based PBX must be simple to use, familiar and relatively cheap. While the H.323 recommendations are pretty expensive, an H.323 proxy can be used to communicate with the Skinny Client using the SCCP.[para] Here the telephone is a skinny client over IP, in the context of H.323. A proxy is used for the H.225 and H.245 signaling. Skinny messages are carried above TCP and use the port 2000 at the same time the skinny client (i.e. an Ethernet Phone) uses TCP/IP to transmit and receive calls and RTP/UDP/IP to/from a Skinny Client or H.323 terminal for audio.

The Skinny Call Control Protocol (SCCP, or short Skinny) is a proprietary network terminal control protocol originally developed by Selsius Corporation.

The SCCP technology is now owned and defined by Cisco Systems, Inc. as a messaging system between a Skinny client and the Cisco CallManager. Examples of skinny clients include the Cisco 7900 series of IP phones, Cisco IP Communicator softphone and the 802.11b wireless Cisco 7920, along with Cisco Unity voicemail server. Skinny is a lightweight protocol which allows for efficient communication with Cisco CallManager. CallManager acts as a signaling proxy for call events initiated over other common protocols such as H.323, SIP, ISDN and/or MGCP.

A Skinny client uses TCP/IP to communicate with one or more Call Manager applications in a cluster. It uses the Real-time Transport Protocol (RTP) over UDP-transport for the bearer traffic (real-time audio stream) with other Skinny clients or an H.323 terminal. SCCP is a stimulus-based protocol and is designed as a communications protocol for hardware endpoints and other embedded systems, with significant CPU and memory constraints.

Cisco acquired SCCP technology when it acquired Selsius Corporation in 1998.As a remnant of the Selsius origin of the current Cisco IP phones, the default device name format for registered Cisco phones with CallManager is SEP -- as in Selsius Ethernet Phone -- followed by the MAC address. Cisco also has marketed a Skinny-based softphone called Cisco IP Communicator.