initial domain identifier (ATM) (IDI)
The Initial Domain Identifier (IDI) is included in the header of the OSI address and is part of the NSAP formattedATM address.
For the OSI address, the Initial Domain Identifier is a data field in the Network Service Access Points (NSAP); for ATM, it specifies the address mapping and management affiliation. The IDI data field corresponds in the ATM addresses to the data fields of the Data Country Code( DCC), the International Code Designator( ICD) and the address information according to E.164.