MSTP has different port roles. Which of the following statements are correct? (Multiple choice)
A . The internal path cost saved by the edge port of the domain is greater than the internal path cost saved by the non-domain edge port.
B . Backup port as a backup of the root port, providing another switchable path from the designated bridge to the root.
C . When the MSTP calculation is performed, the role of the domain edge port on the MSTI is different from that of the CIST instance.
D . The master port is a special domain edge port. The role of the master port on the CIST is the root port. The role of the master port is the master port.
Answer: ABD