Why does the lossy nature of standard Ethernet make it unsuitable for a layered FCoE implementation? How does Converged Enhanced Ethernet (CEE) address this problem?

Traditional FC manages congestion through the use of a link-level, credit-based flow control that guarantees no loss of frames.

Conventional Ethernet is lossy in nature, which means that frames might be dropped or lost during transmission. Typical Ethernet, coupled with TCP/IP, uses a packet drop flow control mechanism. The packet drop flow control is not lossless and hence is unsuitable for a layered FCoE implementation.

Converged Enhanced Ethernet (CEE) address this problem by providing a new specification called Priority-Based Flow Control (PFC), to the existing Ethernet standard that eliminates the lossy nature of Ethernet.

PFC provides a link level fl ow control mechanism. PFC creates eight separate virtual links on a single physical link and allows any of these links to be paused and restarted independently. PFC enables the pause mechanism based on user priorities or classes of service. Enabling the pause based on priority allows creating lossless links for traffic, such as FCoE traffic. This PAUSE mechanism is typically implemented for FCoE.