This read-only value reports the internal NSAP address assigned by the switch to this port, formatted as a 13-byte node prefix followed by a 7-byte port number, and it automatically updates its node-prefix portion whenever the switch's node prefix changes (which itself cannot be changed while connections exist on the switch). It lets an admin see the exact address the switch uses to identify this port for soft permanent virtual connection (SPVC) routing. For example, an admin troubleshooting an SPVC that fails to route to a specific port would compare this address against the configured SPVC endpoint address to confirm they match.