Q-Logic 8100 SERIES manual What is Enhanced Ethernet?, What is Fibre Channel over Ethernet FCoE?

1–Product Overview

What is Enhanced Ethernet?

What is Enhanced Ethernet?

Standard Ethernet is a best-effort network that may drop packets or deliver packets out of order when the network is busy or congested, resulting in retransmissions and time-outs. The SCSI payload carried by the Fibre Channel protocol does not react well to dropped or out-of-order packets. Therefore, standard Ethernet is not an acceptable choice to carry Fibre Channel payloads.

To enable the transport of Fibre Channel frames over Ethernet, several enhancements were added to standard Ethernet. These enhancements have been ratified in the following IEEE and IETF standards:

Priority flow control (IEEE 802.1Qbb)

Congestion notification (IEEE 802.1Qau)

Link layer routing protocol (IETF–TRILL)

Enhanced transmission selection (802.1Qaz)

Standard Ethernet with these enhancements is known as enhanced Ethernet (EE), converged enhanced Ethernet (CEE), lossless Ethernet, or data center Ethernet (DCE).

What is Fibre Channel over Ethernet (FCoE)?

FCoE provides a way to transport Fibre Channel frames on top of an Ethernet infrastructure. In summary, unaltered Fibre Channel frames are encapsulated in an Ethernet header, sent over a lossless Ethernet fabric, and unencapsulated when they reach the target (Figure 1-1). Because protocol conversion tables and state tables are not required, FCoE is considered to be a gateway-less technology.

Figure 1-1. Encapsulated Fibre Channel

The FCoE architecture is based on the Fibre Channel protocol, and provides the same host-to-switch and switch-to-switch connectivity as Fibre Channel fabrics. FCoE also provides the same level of management and security found in Fibre Channel through the use of zoning and port worldwide name-based port security.

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