Satellite link as backup in critical network infrastructures
The operational continuity of data centres and mission-critical network nodes depends on the availability of multiple independent communication paths. When the primary terrestrial connectivity, typically based on optical fibre, experiences an interruption due to a physical cause, logical failure or security incident, the satellite link acts as an out-of-band backup path. This topological independence is precisely its differential value: by not sharing physical infrastructure with the primary access, the space segment remains operational in scenarios where the terrestrial plant is compromised. From a functional standpoint, the backup satellite link is used primarily for three management functions: out-of-band access to network equipment and control systems, time synchronisation by means of GNSS signals or timing references distributed over the link itself, and continuous telemetry of the status of critical nodes to remote operations centres. Out-of-band management allows operators to maintain visibility and intervention capability over the infrastructure even when the data and control planes of the primary access have collapsed, materially reducing diagnosis and recovery time. Capacity planning for this type of architecture requires dimensioning the satellite link in accordance with the traffic strictly necessary for management and recovery functions, not to replace the bandwidth of the primary access. This criterion determines the choice of orbit and terminal class: geostationary orbit solutions offer consolidated availability and predictable latencies suitable for management protocols; low-orbit constellations present lower latencies, although they require handover management between satellites that must be evaluated in the context of each critical application. Redundancy of the satellite ground segment itself, including antennas and modems, must form part of the design. An aspect frequently underestimated in business continuity planning is the periodic verification of switchover. A backup satellite link that is not activated and validated on a regular basis may exhibit silent degradations in configuration, authentication or time synchronisation that are only detected at the moment of actual need. Test procedures must include the full activation of the alternative path, verification of the out-of-band management routes and checking of the temporal accuracy delivered by the link, with results documented as part of the audited continuity plan. For operators of critical infrastructures and EU public administrations, the integration of satellite backup into business continuity plans also responds to sector-specific regulatory frameworks that require the demonstration of resilience in the face of connectivity failures. The independence of the space segment with respect to the threats affecting the terrestrial plant, combined with a correctly dimensioned and verified out-of-band management architecture, constitutes a concrete technical element within a network resilience strategy that is documentable and auditable.
NASSAT - Network Satellite Systems