General Recommendations for NSAP Addresses

Use an Administrative Prefix obtained from a national or international authority if at all possible. An authority does not have to reside in the same country as the petitioning organization (for example, a company in Spain could petition AFNOR for an Organization Identifier).

If the Local Format is to be used, the network must be completely isolated from public network traffic. If a customer needs a temporary AP, they should use a International Telephone Number, or the X.121 format.

Use the binary AFI value whenever possible.

If using a temporary AP, limit the length of the PAP to 14 octets or less. This will allow the PAP to fit into the space allowed by a national or international authority's AP in the future.

If using an AP allocated by an international or national authority, define all 20 octets of the NSAP, even if this means allocating a reserved field.

Define and manage the PAP address structure independent of the AP. This will make managing multiple AP values, or migrating between AP values easier. This especially includes the following fields:

All the above fields should be unique regardless of AP value, even if the authorities administering the APs have defined the full DSP. For instance, if a network administrator is managing a MAP network and a U.S. GOSIP network, the values used in the Subnet ID fields for the MAP network NSAP addresses should not be reused in the Area ID values in the U.S. GOSIP NSAP addresses.

All fields should be defined to fall on octet boundaries, that is, they should always contain an even number of hexadecimal digits.

To be compatible with the ISO IS-IS Routing Protocol, the last three fields of the PAP should conform to the 2/6/1 format.