PCA network capacity can be expanded by adding up to five mated triplets of PCA. PCA mated triplets added after the PCA network is up and running cannot include additional Binding SBR servers.
Every PCA mated triplet must have the same number of Session SBR server groups, though not every mate within a mated triplet must have the same number of server groups. Once the number of SBR server groups is selected, the value cannot be changed until a software upgrade becomes available that supports SBR growth or both functions are disabled. A maximum of eight SBR server groups is supported per resource domain instance, and for a mated triplet, a quantity of eight server groups results in three server groups at each of two mates, and two server groups at one mate.
While SBR growth (i.e. adding SBR server groups) is currently not supported, PCA MP servers can be added as needed (up to a maximum of 16 DA-MPs) to support the desired level of Diameter signaling traffic.