X.25 (4)
X.121 addresses
- IDN International Data Number (address)
- DNIC - Data Network Identification Code (optional)
- NTN - National Terminal Number (variable size)
- PSN - Packet Switched Network
-
- IDN = DNIC (4 digits) + NTN (up to 10 digits)
- DNIC = Country (3 digits) + PSN (1 digit)