R1 redundancy on the left is functionally equivalent to S2 redundancy, without the single point of failure in the NAP. R2 redundancy adds yet another level of assurance and high availability.
R1 and R2 System Redundancy
R1 redundancy on the left is functionally equivalent to S2 redundancy, without the single point of failure in the NAP. R2 redundancy adds yet another level of assurance and high availability.