http://www.rfc-editor.org/rfc/rfc7092.txt
RFC 7092: A Taxonomy of Session Initiation Protocol (SIP) Back-to-Back User Agents, H. Kaplan, V. Pascual2013-12-01T23:00:00-00:00There are numerous types of SIP B2BUAs performing different roles in different ways; for example, IP Private Branch Exchanges (IPBXs), Session Border Controllers (SBCs), and Application Servers (ASs). This document identifies several common B2BUA roles in order to provide taxonomy other documents can use and reference.