the UNL

the Uniform Network Location is the effective IP address where a user agent (a client) or other mobile entity is operating for a user (or other UNI), usually in combination with an allocated port number. UNLs are volatile, as the current IP number of a client changes frequently, and are typically given to trusted friends for peer-to-peer activity. Usually the UNL points to the root entity of the user's client.

Example: psyc://localhost:4711/

NOTE: How locations work and how they are linked to the identity is not covered in this Specification