In a SONET or SDH frame, overhead of nine octets dedicated to framing, span performance, error monitoring, and the transport of status, messages, and alarm indications for the maintenance of links connecting section terminating equipment (STE), which can be repeaters, add/drop multiplexers, or anything else that attaches to either end of a fiber link.The repeaters can be standalone or built into switches, such as digital cross connect systems (DCCSs). SOH and Line Overhead (LOH) comprise Transport Overhead (TOH). See also ADM, frame, link, LOH, octet, SDH, SONET, and TOH.