Defines at what congestion level the incoming packets on this
port should be discarded in the network.
CNGC_DISCARD_AT_LVL_TWO - Discard FR DE packets at level 2,
discard FR non DE packets at level 4,
discard SMDS packets at level 3,
discard IP packets at level 3.
Default value
CNGC_DISCARD_AT_LVL_ONE - discard all at level 1
CNGC_DISCARD_AT_LVL_TWO - discard all at level 2
CNGC_DISCARD_AT_LVL_THREE - discard all at level 3
CNGC_DISCARD_AT_LVL_FOUR - discard all at level 4