Refer to the exhibit. How should you redesign this network running BGP to improve availability of the routers A1 and 1B at the core site?

BGP PIC (Prefix Independent Convergence) accelerates failover when a path is lost but does not eliminate the hardware failure risk of either individual router.

Graceful Restart allows BGP sessions to survive a control-plane restart but does not protect against a complete hardware failure of either router.

Link bundles improve link-level redundancy and bandwidth aggregation but do not address the availability of the routing platforms themselves.

A multichassis system (such as Cisco VSS or similar chassis-clustering technology) virtualizes two physical routers into one logical routing entity, so the failure of one chassis does not tear down BGP sessions or disrupt traffic forwarding for connected neighbors. This provides true hardware redundancy at the core, which directly addresses the availability of routers A1 and 1B as a combined system.