IBM Flex System V7000 Expansion Enclosure 4939H29 ユーザーズマニュアル

Draft Document for Review January 29, 2013 12:52 pm

IBM Flex System V7000 Storage Node Introduction and Implementation Guide

 (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 

 in this standard.

1

 The standard also states 

that devices shall guarantee in-order delivery of FCoE frames within the Lossless Ethernet 
network.

2

This 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 DCB standards include: 

��

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 

 (CEE) is now generally accepted by IBM and several other 

vendors in the T11 working group. The official IEEE 802 term is now 

.

The FCoE requirement is the use of a lossless Ethernet, for example one that implements the 
DCB extensions to Ethernet as described above.

The structure of FCoE is that the upper layers of FC are mapped onto Ethernet, as shown in 
Figure 11-8 on page 443. The upper layer protocols and services of FC remain the same in 
an FCoE deployment. For example, zoning, fabric services, and similar functions still exist 
with FCoE. The difference is that the lower layers of FC are replaced by lossless Ethernet. 
Therefore, FC concepts, such as port types and lower-layer initialization protocols must also 
be replaced by new constructs in FCoE. Such mappings are defined by the FC-BB-5 
standard.

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 

2  

ibid (FC-BB-E page 27)