This reports the functional role of the SONET/SDH equipment as one of three categories: ADM (Add/Drop Multiplexer), MUX (Multiplexer), or MSPP (Multi-Service Transport Platform), each describing a different way the network element handles traffic on the transport ring. Administrators use it to understand how a given node fits into the SONET/SDH network architecture, since an ADM adds and drops traffic from a ring while a MUX simply combines circuits. For instance, seeing "ADM" for a node tells an admin it's positioned to add and drop lower-rate traffic from the higher-rate SONET ring rather than acting as an endpoint multiplexer.