468 IBM Flex System V7000 Storage Node Introduction and Implementation Guide
11.4 FCoE connectivity
Fibre Channel over Ethernet (FCoE) is a method of sending Fibre Channel frames directly
over an Ethernet network. It relies on a new Ethernet transport with extensions that provide
lossless transmission of storage data. The new Ethernet transport standard is the Fibre
Channel - Backbone - 5 (FC-BB-5) standard, which specifies that FCoE is intended to operate
over an Ethernet network that does not discard frames in the presence of congestion. Such
an Ethernet network is called a
lossless Ethernet in this standard.
1
The standard also states
that devices shall guarantee in-order delivery of FCoE frames within the Lossless Ethernet
network.
2
Lossless Ethernet network is achieved by using a new set of Data Center Bridging (DCB)
standards that enhance existing 802.1 bridge definitions. The enhancements provide a
converged network that allows multiple applications to run over a single physical
infrastructure. These DCB standards are intended to apply to more broader type of traffic than
just for FCoE.
The following DCB standards are included:
Priority-based Flow Control–IEEE 802.1Qbb (PFC)
Enhanced Transmission Selection–IEEE 802.1Qaz (ETS)
Congestion Notification–IEEE 802.1Qau (CN)
Data Center Bridging Capabilities Exchange–IEEE 802.1Qaz
There have been a number of terms to describe these DCB standards, but the term
Converged Enhanced Ethernet (CEE) is now generally accepted by IBM and several other
vendors in the T11 working group. The official IEEE 802 term is now
Data Center Bridging.
1
American National Standards Institute, Inc., Fibre Channel — Fibre Channel Backbone - 5 (FC-BB-5), 4.4.4,
“QoS and bandwidth” on page 26 at http://fcoe.com/09-056v5.pdf
2
ibid (FC-BB-E page 27)
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