This counter tracks the number of BGN (Begin) PDUs transmitted on this port, per the description, where BGN is the SSCOP message that initiates establishment of the signaling data link before any Q.93b messages can flow. Because BGN only needs to be sent once per SSCOP connection setup (not per call), a healthy stable trunk should show this counter incrementing rarely, while frequent BGN transmissions indicate the underlying signaling link is repeatedly dropping and having to reestablish itself. This makes it a strong link-stability indicator distinct from the per-call SVC counters.