UNKNOWN
Unknown is a virtual protocol created for DPI that represents flows that are not recognized by the system. Most of the time, its presence is due to the existence of a business application whose specifications are not made available to the public. Such flows can be defined in the system by means of a User Defined Application.
Available to all SRX running 12.3X48+
Available to all MX running 20.2R1+
Available to all vSRX running 20.3R1+