About 9000 32R1 clock domain configuration, which of the following are correct?()

A.A CSTM board can be configured with 2 subcards, in total 8 STM-1 ports. Each port can be configured with at most 21 clock domains, and so each subcard at most 84 clock domains.

B.One CSTM board's four ports cannot be configured with repeated clock domain number. For example, if 4/1/9 is configured with clock domain 1, other ports on the board cannot be configured with clock domain 1 any longer.

C.CSTM board's clock domain doesn’t support trans-port. For example, if 1-1-1 of 4/1/9 belongs to clock domain 1, E1 of other ports cannot be configured into the same clock domain.

D.Each clock domain of CSTM port must include one of the first 21 E1s (1-1-1 to 1-7-3).