This read-only counter tallies frames not transmitted successfully by this adapter, being the sum of its deferred transmissions, late collisions, excessive collisions, carrier sense errors, and internal MAC transmit errors. An admin uses this as a rolled-up transmit-error indicator, then checks the individual component counters when it rises to find the specific root cause. For example, if this counter climbs, an admin would check cpqNicIfPhysAdapterLateCollisions next since late collisions specifically point to a cabling or segment-length problem.