When you use code generation, this declaration is automatically created in the deployment.h file.
There is an example of a such enum declaration:
typedef enum
{
  node1_partition_secret_outgoing_global = 0,
  node1_partition_topsecret_outgoing_global = 1,
  node1_partition_unclassified_outgoing_global = 2,
  node2_partition_secret_incoming_global = 3,
  node2_partition_topsecret_incoming_global = 4,
  node2_partition_unclassified_incoming_global = 5
} pok_port_identifier_t;