Skinny Client Control Protocol

From Wikipedia, the free encyclopedia

SCCP is a proprietary terminal control protocol originally developed by Selsius Corporation. It is now owned and defined by Cisco Systems, Inc. as a messaging set between a skinny client and the Cisco CallManager. Examples of skinny clients include the Cisco 7900 series of IP phone such as the Cisco 7960, Cisco 7940 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 Call Manager. Call Manager acts as a signalling 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 and from one or more Call Managers in a cluster. RTP/UDP/IP is used to and from a similar skinny client or H.323 terminal for the bearer traffic (real-time audio stream). 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 the late 1990s. 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.

Other companies like Symbol Technologies and SocketIP have implemented this protocol in VoIP Terminals (phones) and Media Gateway Controllers or Softswitches.

A company named IPBlue has created a software phone (soft phone) which uses SCCP for signaling, too. This phone in fact appears to the Cisco CallManager server as a 7960 hardware phone.

In addition, Cisco has come out with its own version of a skinny softphone called Cisco IP Communicator as well as SIP-based softphone called Cisco Unified Personal Communicator. Previously, Cisco had a JTAPI/CTI version of a softphone called Cisco IP Softphone.

A summary of SCCP request and response messages is as follows:

  Code       Station Message ID Message
 0x0000   Keep Alive Message
 0x0001   Station Register Message
 0x0002   Station IP Port Message
 0x0003   Station Key Pad Button Message
 0x0004   Station Enbloc Call Message
 0x0005   Station Stimulus Message
 0x0006   Station Off Hook Message
 0x0007   Station On Hook Message
 0x0008   Station Hook Flash Message
 0x0009   Station Forward Status Request Message
 0x11     Station Media Port List Message
 0x000A   Station Speed Dial Status Request Message
 0x000B   Station Line Status Request Message
 0x000C   Station Configuration Status Request Message
 0x000D   Station Time Date Request Message
 0x000E   Station Button Template Request Message
 0x000F   Station Version Request Message
 0x0010   Station Capabilities Response Message
 0x0012   Station Server Request Message
 0x0020   Station Alarm Message
 0x0021   Station Multicast Media Reception Ack Message
 0x0024   Station Off Hook With Calling Party Number Message
 0x22     Station Open Receive Channel Ack Message
 0x23     Station Connection Statistics Response Message
 0x25     Station Soft Key Template Request Message
 0x26     Station Soft Key Set Request Message
 0x27     Station Soft Key Event Message
 0x28     Station Unregister Message
 0x0081   Station Keep Alive Message
 0x0082   Station Start Tone Message
 0x0083   Station Stop Tone Message
 0x0085   Station Set Ringer Message
 0x0086   Station Set Lamp Message
 0x0087   Station Set Hook Flash Detect Message
 0x0088   Station Set Speaker Mode Message
 0x0089   Station Set Microphone Mode Message
 0x008A   Station Start Media Transmission
 0x008B   Station Stop Media Transmission
 0x008F   Station Call Information Message
 0x009D   Station Register Reject Message
 0x009F   Station Reset Message
 0x0090   Station Forward Status Message
 0x0091   Station Speed Dial Status Message
 0x0092   Station Line Status Message
 0x0093   Station Configuration Status Message
 0x0094   Station Define Time & Date Message
 0x0095   Station Start Session Transmission Message
 0x0096   Station Stop Session Transmission Message
 0x0097   Station Button Template Message
 0x0098   Station Version Message
 0x0099   Station Display Text Message
 0x009A   Station Clear Display Message
 0x009B   Station Capabilities Request Message
 0x009C   Station Enunciator Command Message
 0x009E   Station Server Respond Message
 0x0101   Station Start Multicast Media Reception Message
 0x0102   Station Start Multicast Media Transmission Message
 0x0103   Station Stop Multicast Media Reception Message
 0x0104   Station Stop Multicast Media Transmission Message
 0x105    Station Open Receive Channel Message
 0x0106   Station Close Receive Channel Message
 0x107    Station Connection Statistics Request Message
 0x0108   Station Soft Key Template Respond Message
 0x109    Station Soft Key Set Respond Message
 0x0110   Station Select Soft Keys Message
 0x0111   Station Call State Message
 0x0112   Station Display Prompt Message
 0x0113   Station Clear Prompt Message
 0x0114   Station Display Notify Message
 0x0115   Station Clear Notify Message
 0x0116   Station Activate Call Plane Message
 0x0117   Station Deactivate Call Plane Message
 0x118    Station Unregister Ack Message