Short answer
FirstNet matches Direct Routing resilience to how critical each site is: a standard managed SBC for single-site or non-critical calling, a high-availability SBC pair for critical and multi-site organisations, or full geographic redundancy across two FirstNet SBC clusters.
In detail
The options in more detail:
- Standard SBC: a single managed SBC set-up for single-site or non-critical Teams calling, where moderate downtime is tolerable.
- HA SBC pair: load-shared, geographically diverse SBCs for critical sites, multi-site enterprises and businesses where downtime has a material impact.
- Geographic redundancy: full high availability across two FirstNet SBC clusters, with a resilient SIP path, where the exposure justifies it.
- Connectivity: primary and backup internet links between your sites and Microsoft 365, because the voice path is only as resilient as that underlay.
FirstNet operates two geographically diverse SBC clusters with load-shared traffic, which form the backbone of the HA designs. Resilience is scoped per site, never assumed by default.
A higher resilience tier improves the design but does not change the contractual SLA, which covers the FirstNet-managed SBCs, SIP trunk, number provisioning and support. Microsoft's Teams service sits outside FirstNet's SLA, although FirstNet manages the joint escalation for you.
Source: FirstNet Microsoft Teams Calling service page →
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