What is the difference between protocol and service interface in ISO-OSI 7 layer model?

Protocol is the special set of rules that end points in a telecommunication connection use when they communicate. In other Words Protocol is an agreed-upon format for transmitting data between two devices. The protocol determines the following: * the type of error checking to be used * data compression method, if any * how the sending device will indicate that it has finished sending a message * how the receiving device will indicate that it has received a message Service is a program, routine, or process that performs a specific system function to support other programs, particularly at a low (close to the hardware) level