Q: What does "lossless" mean as it relates to Fibre Channel over Ethernet (FCoE)?

A: One of the early benefits of Fibre Channel storage was the fact that its communications had extremely high performance. A factor in that high performance was that all Fibre Channel traffic was sent in a lossless fashion: A packet of data sent from a SAN was guaranteed to arrive at its server initiator. Constructing the protocol in this way meant eliminating the network acknowledgements (that, for example, TCP/IP requires) to verify the packet was received.

Although this method worked great when Fibre Channel's cabling infrastructure was fiber optics, it became a challenge as IT departments moved Fibre Channel to traditional, copper Ethernet cabling. That's because TCP/IP by itself isn't a lossless protocol.