Under what circumstances is the root port selected, and the port ID is compared when specifying the port?

When selecting the root port, when the port-to-root bridge overhead value and the peer bridge ID are all the same, the peer port ID size needs to be compared, and the small one is preferred; 2. When selecting the specified port, when the port-to-root bridge overhead value and the local bridge ID are all the same, the local port ID size needs to be compared, and the small one is preferred.