val get_checksum : Cstruct.t -> Cstruct.uint16val set_checksum : Cstruct.t -> Cstruct.uint16 -> unitval get_id : Cstruct.t -> Cstruct.uint16val set_id : Cstruct.t -> Cstruct.uint16 -> unitval get_seq : Cstruct.t -> Cstruct.uint16 -> unitval set_seq : Cstruct.t -> Cstruct.uint16 -> unit