1. Introduction

This document specifies a protocol for efficiently routing multicast groups that may span wide-area (and inter-domain) internets. This protocol is called Protocol Independent Multicast - Sparse Mode (PIM-SM) because, although it may use the underlying unicast routing to provide reverse-path information for multicast tree building, it is not dependent on any particular unicast routing protocol.

PIM-SM Version 2 was specified in RFC 4601 as a Proposed Standard. This document is intended to address the reported errata and to remove the optional (,,RP), PIM Multicast Border Router features and authentication using IPsec that lacks sufficient deployment experience, to advance PIM-SM to Internet Standard.

This document specifies the same protocol as RFC 4601, and implementations per the specification in this document will be able to interoperate successfully with implementations per RFC 4601.