http://www.rfc-editor.org/rfc/rfc5729.txt
RFC 5729: Clarifications on the Routing of Diameter Requests Based on the Username and the Realm, J. Korhonen, M. Jones, L. Morand, T. Tsou2009-12-01T23:00:00-00:00This specification defines the behavior required of Diameter agents to route requests when the User-Name Attribute Value Pair contains a Network Access Identifier formatted with multiple realms. These multi-realm, or "Decorated", Network Access Identifiers are used in order to force the routing of request messages through a predefined list of mediating realms. [STANDARDS-TRACK]