Control and Status Protocol
Control and Status Protocol (CSP) runs between the CB and attached PE units and is
used to bring the PE units up or down.
PE CSP executes as an upper layer protocol over the Edge Control Protocol (ECP). ECP provides acknowledgment and retransmission of packets. PE CSP assumes that once a protocol data unit (PDU) is delivered to ECP, the PDU is reliably delivered to its peer.
PE CSP is implemented as a simple command and response protocol with protocol information packaged in Type-Length-Value (TLV) triplets. Each PE CSP PDU consists of a command TLV and zero or more additional TLVs. A separate control E-channel is created between the CB and PE unit to carry PDUs, and a single instance of CSP runs between the PE unit and the CB.