Cisco Certified Network Associate (CCNA) Practice Exam

What bit of the Frame Relay frame header indicates congestion in the opposite direction that the frame is traveling?

1. Data Link Connection Identifier (DLCI)

2. Forward Explicit Congestion Notification (FECN)

3. Backward Explicit Congestion Notification (BECN)

4. Frame Relay Traffic Descriptor (FRTD)

The correct answer is: Backward Explicit Congestion Notification (BECN)

The chosen answer, which refers to the Backward Explicit Congestion Notification (BECN), is correct because it specifically indicates congestion in the opposite direction of traffic flow in a Frame Relay network. BECN is used to notify the sender that congestion is occurring on the network, allowing the sender to take precautions such as reducing the rate of data transmission to help alleviate congestion. When congestion is detected on a particular segment of the network, the BECN is set in the frame header as it travels towards the sender. This mechanism helps manage network traffic more effectively by alerting sources to adapt their sending behavior according to current network conditions, thus maintaining overall network performance and reliability. The Data Link Connection Identifier (DLCI) is primarily used for identifying the virtual circuit used for the connection and does not provide information about congestion. The Forward Explicit Congestion Notification (FECN), while related to congestion, indicates that congestion is occurring in the forward direction (towards the destination), rather than the reverse. The Frame Relay Traffic Descriptor (FRTD) pertains to traffic management and monitoring but does not indicate specific congestion notifications like BECN does.