code: def authenticationRequest():
      
      a = TpPd(pd=0x5)
      b = MessageType(mesType=0x12)  # 00010010
      c = CiphKeySeqNrAndSpareHalfOctets()
      d = AuthenticationParameterRAND()
      packet = a / b / c / d
      return packet
docs: AUTHENTICATION REQUEST Section 9.2.2