UPSR protection switching is initiated by （）, while BLSR is initiated by （）.

单项选择题On an ONS 15454 node you can tunnel an （）.

A. SDH circuit over a SONET network delivering it as an SDH signal
B. SDH circuit over a SONET network delivering it as a SONET signal
C. SONET circuit over an SDH network delivering it as an SDH signal
D. SONET circuit over an SDH network delivering it as a SONET signal

单项选择题In order to avoid misconnections due to a failed node in a Bidirectional Line Switched Ring (BLSR), Alarm Indication Signals (AISs) are sent on every channel normally terminating in that node. What is the name of this process?（）

A. trunking
B. squelching
C. nodal bypass
D. bridge and roll
E. node failure insertion

单项选择题How is UPSR and BLSR traffic rerouted during a protection switch when a complete fiber cable cut occurs?（）

A. Traffic is switched from the first node receiving the AIS indication.
B. Traffic is switched from the far side of the failure, allowing handshaking to occur.
C. UPSR traffic is switched from the terminating node, BLSR traffic is rerouted from the originating node in the ring.
D. UPSR traffic is switched from the terminating node, circuit by circuit. BLSR traffic is rerouted from the last reachable node in the ring.

单项选择题What protection method is used in 4F BLSR networks?（）

A. Each fiber has half of its SONET capacity reserved for protection.
B. Two fibers in the span carry working traffic, while the other two fibers in the span are reserved for protection.
C. The signal is sent simultaneously in both directions around the ring. The receiver determines which fiber to listen to based on signal quality.
D. The signal is sent simultaneously in both directions around the ring. The transmitter determines which fiber has the working bit set for the receiver to acknowledge.

单项选择题Which is a legitimate bandwidth matched pair?（）

A. DS-1; E1
B. DS-1; STM-1
C. OC-3; STM-1
D. STS-1; STM-1
E. OC-192; STM-192