Buying two telecommunications circuits does not automatically provide resilient connectivity. True diversity depends on the physical route, carrier infrastructure, building entrance, local exchange, upstream transport and logical routing dependencies.
Start with the service requirement
Define the applications and services that must remain available, their bandwidth, latency and recovery requirements, and whether the data center must remain reachable during loss of one provider or one building entrance.
Verify physical diversity
Two circuits may share the same underground duct, pole route, manhole, carrier node or building entry. Where resilience is required, request documented route diversity and review the external and internal paths rather than relying only on different circuit IDs.
Use independent building entrances where justified
Critical sites may use separated carrier entrance facilities or meet-me-room arrangements so a localized civil incident does not isolate every external connection. The degree of separation should be consistent with the facility risk and availability objective.
Understand logical dependencies
Different physical fibers can still converge onto the same provider router or upstream autonomous-system path. Review provider architecture, BGP policy, default-route dependencies and any shared managed equipment.
Protect demarcation equipment
Carrier Network Termination Equipment and demarcation devices require reliable power, environmental protection and monitoring. A dual-carrier strategy can still fail if both circuits terminate on one unprotected device or single power source.
Test failover
Resilience should be demonstrated by controlled testing. Verify loss of each carrier, edge router, external path and power source; confirm routing convergence, application reachability, alarm generation and recovery.
References and further reading
- ANSI/TIA-942-C, Telecommunications Infrastructure Standard for Data Centers.
- ISO/IEC TS 22237-5:2018, Telecommunications cabling infrastructure.
- IETF RFC 4271, Border Gateway Protocol 4.
