Port Extension Control and Status Protocol
The Port Extension Control and Status Protocol (PE-CSP) is a simple request/response protocol that runs over ECP and is initiated upon detection of a bridge port extender using the LLDP protocol. Each controlling bridge (CB) has a single PE-CSP protocol instance on each cascade port. In the case of a cascade port that is a LAG, the PE-CSP instance runs on the LAG and transmits on the current master port in the LAG. There is a separate PE-CSP session per LAG member port, but configuration commands are sent over a chosen single port in the LAG.
Each PE-CSP PDU is made of a command TLV and zero or more additional TLVs.
Example PE-CSP Protocol Exchange shows a typical PE-CSP exchange between a CB and a bridge port extender (BPE).