Which option is a fate-sharing characteristic in regards to network design?

In a fate-sharing design, multiple services or components are co-located or share a common dependency such as a single control plane, forwarding engine, or link. When that shared element fails, every service dependent on it fails simultaneously - they share the same fate. This is a key risk factor in availability analysis and motivates design choices such as separating control planes, using redundant paths, and avoiding single points of failure.

Protection against distribution layer failures describes redundancy and resilience techniques such as dual-homing or fast reroute, which are design responses to fate-sharing risks, not the definition of fate-sharing itself.

A stateful forwarding device maintains session or flow state such as NAT bindings or firewall sessions - this describes a forwarding plane characteristic and is unrelated to the fate-sharing concept.

Data sequencing and acknowledgment mechanisms are transport layer functions associated with TCP's reliable delivery service, not a network architectural fate-sharing characteristic.