SSCOP - Service Specific Connection Oriented Protocol

SSCOP - Defined in ITU Q.2110, "B-ISDN SAAL Service-Specific Connection-Oriented Protocol (SSCOP)," the Service Specific Connection Oriented Protocol is responsible for providing mechanisms for the establishment, release and monitoring of signaling information exchanged between peer signaling entities. SSCOP is positioned within the AAL architecture as per the figure below:

                         SAAL SAP
                            ^
                            |
                            V                           
              SSCF-UNI  Q.SAAL.2  SSCF-NNI      Q.SAAL.3
                            ^
                            |
                            V
                          SSCOP                 Q.SAAL.0
                            ^
                            |
                            V
                           CPCS   \
                            ^      \
                            |       | I.363 Para. 6 (AAL5 Common Part)
                            V      /
                           SAR    /
                            ^
                            |
                            V
                         ATM SAP

SSCOP provides many of the same services for Q.2931 signalling that TCP provides for IP. Some of these services are:

• Flow control. A switch or end system can control the rate at which it receives signalling messages
• Error handling and sequencing. Since each SSCOP PDU contains a sequence number, SSCOP can determine if one has been lost and request retransmission. SSCOP can also ensure sequential integrity by using these sequence numbers.
• Connection establishment and resynchronization. Involves negotiation of buffer sizes and other transfer characteristics and renegotiation of these parameters should a connection fail.
• Polling and status exchange. The health of a connection is monitored via exchange of status messages and connections are maintained through use of keep alive messages.

• Kyas, Othmar. "ATM Networks" pp. 179-188. ISBN (International Thomson Pubs, UK) 1-850-32128-9, (Van Nostrand Reinhold, USA) 0-442-02000-2

• ATM - Asynchronous Transfer Mode
• AAL - ATM Adaptation Layer
• SAAL - Signaling AAL
• CPCS - Common Part Convergence Sublayer
• SAR - Segmentation and Reassembly
• SSCS - Service Specific Convergence Sublayer
• SSCF - Service Specific Coordination Function
• SAP - Service Access Point
• UNI - User to Network Interface
• NNI - Network to Network Interface