  TYPE
    nat$protocol = 0 .. nac$max_protocol;

  CONST {supported values for nat$protocol}
    nac$unknown_protocol = 0,
    nac$osi_clns = 2,
    nac$osi_transport = 3,
    nac$cdna_session = 4,
    nac$cdna_virtual_terminal = 5,
    nac$osi_session = 6,
    nac$osi_presentation = 7,
    nac$non_cdna_osi_sess_tp4_clns = 8,
    nac$non_cdna_osi_pres_tp4_clns = 9,
    nac$non_cdna_osi_pres_tp0_cons = 10,
    nac$non_cdna_osi_pres_tp2_cons = 11,
    nac$non_cdna_osi_pres_tp4_cons = 12,
    nac$stream_socket = 13,
    nac$datagram_socket = 14,
    nac$max_protocol = 255;
