Which two new port roles does RSTP introduce?

Rapid Spanning Tree Protocol (RSTP) introduces the roles of "Alternate" and "Backup" ports, which enhance network redundancy and improve convergence times compared to the legacy Spanning Tree Protocol (STP).

The "Alternate" port role serves as a backup path to the Root Bridge and takes over if the primary port experiences a failure. This role allows for faster reconvergence of the network when links fail, as it can immediately transition to the forwarding state without the need for the longer, traditional STP timers.

The "Backup" port role is used on segments where there are redundant links to the same device. It provides an additional level of redundancy by allowing for an alternate path if the primary link fails, although the Backup role is not as commonly implemented as Alternate.

In summary, the introduction of these two roles in RSTP significantly enhances the efficiency of the spanning tree by reducing the time to respond to topology changes and providing more options for path redundancy. This is especially beneficial in enterprise environments where network reliability and performance are critical.