SRv6 Extensions for RDMA Multicast Delivery

This document specifies SRv6 (Segment Routing over IPv6) extensions for multicast delivery of RDMA (Remote Direct Memory Access) Reliable Connection (RC) traffic. It defines a new SRv6 endpoint behavior, End.MT, that performs per-receiver RDMA Base Transport Header (BTH) modifications at edge nodes of the multicast tree. It also specifies procedures for hop-by-hop aggregation of RDMA ACK, NACK, and CNP response messages along the reverse path. Together, these extensions allow RDMA RC endpoints to communicate using standard point-to-point Queue Pair (QP) semantics while the network distributes data packets over an IP multicast tree. Target deployment scenarios include multi-replica distributed storage writes, HPC collective communications, AI training parameter distribution, and large-scale inference KV cache distribution.