This document depicts many common Voice over IP (VoIP) use cases for Session Initiation Protocol (SIP) peering. These use cases are categorized into static and on-demand, and then further subcategorized into direct and indirect. These use cases are not an exhaustive set, but rather the most common use cases deployed today. Status of This Memo This document is not an Internet Standards Track specification; it is published for informational purposes. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see Section 2 of RFC 5741. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc6405.