PIM SSM scaling can be increased to 256k (S,G)s using the pim-ssm-scaling command. This command enables (S,G) scaling for PIM SSM in the global routing table only. The current scaling limitation of (S,G)s per complex (FP) still exist. However, the 256K (S,G)s can be configured over multiple complex to achieve this higher scaling.
When PIM SSM scaling is enabled, the following multicast features are disabled:
DM
MoFRR
JP policy
SSM groups
(S,G) programming is a maximum of 32000 per complex
InBand features (BIER and MLDP)
Extranet
ASM
This feature is only supported on CPM5s.
When this command is enabled and there is a mix of FP3 and FP4 cards in the system, Nokia recommends that configure mcast-management chassis-level per-mcast-plane-capacity total-capacity be set to dynamic so that the system dynamically chooses the lowest denominator throughput card as multicast plane throughput.
To achieve fast failover when PIM SSM scaling is enabled, the default MCID is used which results in the multicast traffic being sent to all line cards and silently discarded where there is no receiver for that traffic. Consequently, the maximum achievable plane capacity for this traffic is constrained to that of the lowest performance FP. When the maximum link capacity from the fabric to the lowest-performance FP is reached, the link to that FP is overloaded causing the fabric to back-pressure the ingress and resulting in packet loss for all FPs. By using the default MCID, this capacity constraint is independent of whether the lowest-performance FP has a receiver on it or not.
If the multicast management chassis per-plane total capacity is configured to an explicit value which is larger than that supported by the lowest-performance FP, IMPM believes there is more plane capacity available than there really is and the result is (S,G) packet loss instead of blackholing.
By setting the multicast management chassis per-plane total capacity to dynamic, the system automatically sets the switch fabric multicast plane capacity to the minimum value supported by the fabric and all line cards in the system. IMPM then has the correct view of the available plane capacity and correctly blackholes (S,G)s when insufficient plane capacity is available. The total maximum multicast capacity is still constrained by the lowest-performance FP.