When the BFD detection intervals on both ends are 30ms and 40ms, are the following options described correctly? An

During BFD session establishment, both ends negotiate operational parameters. The detection interval is determined by the slower of the two configured devices to ensure that neither is overwhelmed. The local system compares its desired minimum transmit interval with the remote system's required minimum receive interval. The actual transmit interval will be the greater of these two values. Consequently, the session will adopt the slower interval, which is 40ms in this scenario. The final detection time is this negotiated interval multiplied by the detection multiplier.

B: The session cannot operate at 30ms because one end has specified a 40ms interval, which is the slowest rate the session can reliably maintain. C: BFD sessions operate on a single set of negotiated parameters for timing. The two ends do not operate at their own independent intervals. D: A mismatch in desired detection intervals is a normal condition that is resolved during negotiation; it does not prevent session establishment.

Huawei NE40E-X8 V800R010C10SPC500 Product Documentation, Feature Description > Reliability > BFD for... > BFD Principles > BFD Session Negotiation. The documentation states, "The system with the larger BFD interval value determines the BFD interval of the session." This confirms the slower rate (40ms) is chosen.

IETF RFC 5880, "Bidirectional Forwarding Detection (BFD)", Section 6.8.7, "Transmitting BFD Control Packets". This section details the negotiation logic where the transmission interval is the maximum of the local bfd.DesiredMinTxInterval and the received bfd.RequiredMinRxInterval.