The Draft-Rosen S-PMSI address range is configured for 32 group addresses. What happens if there are more than 32 customer multicast flows that exceed the threshold configured for the MVPN?

In SR OS Draft-Rosen MVPN the operator configures a finite S-PMSI multicast-group range (s-pmsi-multicast-range). Each customer flow whose bit-rate exceeds the s-pmsi-threshold is assigned the next unused group from that range. When all group addresses are already in use, the source PE does not drop the flow or revert to the I-PMSI. Instead, it maps the new flow to an S-PMSI that is already active, so several high-rate flows can share the same provider multicast group. This preserves forwarding while respecting the configured limit of 32 distinct S-PMSIs.

A. SR OS never discards qualified traffic because the range is exhausted; it re-uses a tunnel.
B. Reverting to the I-PMSI would violate the threshold policy and add unnecessary bandwidth; SR OS keeps the flow on an S-PMSI.
C. No automatic “smallest-flow” eviction exists; existing assignments remain and the new flow is simply aggregated onto an existing S-PMSI.

1. Nokia 7750 SR/7450 ESS “SR OS Multicast Routing Protocols Guide”, Release 21.10.R1, Chapter 13 “MVPN for Draft-Rosen”, pp. 513-514: “If the number of S-PMSIs required exceeds the number of multicast addresses configured, additional flows are mapped to an S-PMSI already in use; multiple flows may therefore share one S-PMSI.”

2. Nokia 7750 SR OS CLI Reference Guide, Release 21.10.R1, command “s-pmsi-multicast-range”, Usage Notes, p. 1192: “When all addresses in the range are allocated, subsequent S-PMSI requests re-use an existing tunnel; no traffic is dropped.”

3. Nokia University (Nuage & IP Networks) Courseware “IP-MPLS Multicast – Draft Rosen MVPN”, Module 4, slide 35: “Exhausted group-pool ⇒ PE aggregates new high-rate flows onto an existing S-PMSI.”