This is the 64-bit version of cefAdjBytes, needed to avoid wraparound on adjacencies pushing enough byte volume to overflow the 32-bit counter within a typical monitoring window. Byte counters wrap faster than packet counters for the same traffic rate, so on any adjacency carrying more than a modest sustained bitrate, this 64-bit object is the practical choice for accurate byte accounting over any but the shortest polling intervals. An adjacency sustaining 500 Mbps of outbound traffic would wrap a 32-bit byte counter in about a minute, making this 64-bit counter necessary for accurate accounting at any reasonable SNMP polling interval.