Inside Macintosh: Networking With Open Transport / Part 2 - Open Transport Reference

Chapter 31 - Serial Endpoint Reference / Options

Protocol Level

You use this XTI constant when calling the OTOptionManagement function to establish the protocol type for an option you are using. You specify this value in the level field of the TOption stucture. This function and structure are described in the chapter "Option Management".

enum {
   COM_SERIAL     = 'SERL'
};