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?（）

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

多项选择题SONET Path Terminating Equipment (PTE) requires which three line codes to be supported for DS1 and DS3 circuits?（） (Choose three.)

A.AMI
B.ESF
C.DUS
D.SSM
E.B3ZS
F.B8ZS

单项选择题Which timing mode is appropriate for a SONET NE that is adjacent to a SONET NE using BITS-1 timing source?（）

A.DUS
B.line timing
C.loop timing
D.internal timing
E.through timing