Why don't you read the SRND, page 2-44?
Best Practices
- The link does not have to be redundant. If a redundant link is used, however, latency on failover must not exceed 500 ms.
- Separate QoS classifications and reserved bandwidth are required for Central Controller high-priority and PG high-priority communications.
- Link sizing and configuration must be examined before any major change to call load, call flow, or deployment configuration. This is especially important in the single-link model.
- The link should preferably be a dedicated circuit fully isolated from, and not tunneled across, the highly available (HA) WAN.
Regards,
Geoff