The 1000BASE-SX MM 850nm Small Form-factor Pluggable (SFP) Gigabit Ethernet Transceiver 550m DDM is a hot-swappable input/output device that plugs into a Gigabit Ethernet port or slot, linking the port with the network. The SFP provides full-duplex Gigabit Ethernet connectivity Multimode duplex fiber and has DDM (Digital-Diagnostic-Monitoring) functions. (Cisco part# SFP-GE-S)