The Diameter base protocol specifies mechanisms whereby a given realm
may advertise Diameter nodes and the supported transport protocol.
However, these mechanisms do not reveal the Diameter applications
that each node supports. A peer outside the realm would have to
perform a Diameter capability exchange with every node until it
discovers one that supports the required application. This document
updates RFC 3588, "Diameter Base Protocol", and describes an
improvement using an extended format for the Straightforward-Naming
Authority Pointer (S-NAPTR) application service tag that allows for
discovery of the supported applications without doing Diameter
capability exchange beforehand. [STANDARDS-TRACK]