What are two characteristics of dual-ring interconnect in SDH networks？ （）

• A、 It protects signals against node failures between rings.
• B、 It protects signals against node failure within a single ring.
• C、 It allows for traffic to be preempted when a ring switch occurs.
• D、 Traffic can be dropped and continued at interconnecting nodes.
• E、 It protects preemptible traffic from being dropped when a ring switch occurs.