Futurewei Technologies USA Huawei 2012 NT Lab Huawei 2012 NT Lab Huawei 2012 NT Lab Huawei 2012 NT Lab This document defines an encoding and corresponding packet processing procedures for native IPv6 multicast source routing (MSR6) using a so-called "Recursive Bitstring" (RBS) address structure. The RBS address structure encodes the source-routed multicast tree as a tree of bitstrings. Each router on the tree only needs to examine and perform replication for the one bitstring destined for it. The MSR6/RBS IPv6 extension header encoding and processing is modeled after that of unicast source routing headers, RFC6554 and RFC8754, and shares all elements that can be shared. To support the RBS structure, it is replacing the "Segments Left" pointer to the next segment with two fields to point to the next sub-tree to parse.