Well known protocols already have a Type Field. A public list of which can be found here . For numeric evaluation, the first octet is the most significant octet of this field. The length and type interpretations of this field are mutually exclusive. Therefore when the value of the two octet field is equal to or greater than 0600 hex then it is a Type Field and the value of the Type Field is obtained from the IEEE Type Field Registrar.
Former assignments are still valid.
The Type Field is a very limited space and therefore its assignment will be limited. It is incumbent upon your company administration to ensure that requests for Type Fields be very limited and only on an as needed basis. Requests for multiple Type Fields by the same applicant will not be granted unless the applicaant certifies that they are for unrelated purposes. In particular, only one new Type Field is necessary to limit reception of a new protocol or protocol family to the intended class of devices. Specification of additional protocol identification types within a new protocol to allow similar or related uses without the need for more than one Type Field assignment.