convergence sublayer (ATM) (CS)
The Convergence Sublayer(CS) is a sublayer of the ATM adaptation layer. The CS sublayer supports procedures and functions for converting ATM to non-ATM formats, such as converting ATM protocols to frame relay or switched multimegabit data service( SMDS).
The CS sublayer receives a Service Data Unit( SDU) and extends it with a header and a trailer according to the protocol. The resulting Protocol Data Unit( PDU) is passed to the Segmentation Sublayer( SAR). The CS sublayer has been further subdivided for ATM Adaption Layer( AAL) 3/4 and AAL -5 into a part containing common functions for a group of services, the Common Part Convergence Sublayer( CPCS), and an application-dependent part, the Service Specific Convergence Sublayer( SSCS).
The CS sublayer handles service-dependent functions such as flow control and synchronization control, and compensates for packetization/depacketization effects as well as transmission errors in the form of incorrectly inserted or lost ATM cells.