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fibre channel over Ethernet (FCoE)

Fibre Channel over Ethernet (FCoE) is a multi-company initiative standardized by the American National Standards Institute (ANSI). With FCoE, Fibre Channel data can be transported in a storage network via Ethernet. The advantages lie in the uniform transmission method, which can be used to simplify the structure of data centers and reduce investments. In addition, the data traffic to the computing and storage resources can be organized via a uniform switching fabric. The management model proposed in this context is also consistent with that of Fibre Channel

(FC). The background to these activities

can beseen in the fact that, up to now, different protocols and a different network infrastructure have been used for local area networks (LAN) than for storage area networks (SAN). The former rely on Ethernet and TCP/IP, the latter on Fibre Channel. With the increasing use of 10 Gigabit Ethernet and 40 Gigabit Ethernet in data centers, sufficiently high speeds are available for the operation of storage area networks (SAN). Consolidation

could therefore take place while preserving the storage network infrastructure

The transmission technology of FCoE

Structure of an FCoE frame

Structure of an FCoE frame

With FCoE, the FC data is transported losslessly via a lossless Ethernet. Two protocols are used for this purpose, one for transporting the data, the FCoE protocol, and one for controlling the FCoE connections, the FCoE Initialization Protocol (FIP). In FCoE, the Fibre Channel payload is packed into an FC frame using the FC header. The FC frame is then equipped with an FCoE header and this FCoE frame is transported via Ethernet. Since the reliability requirements of storage networks are extremely high, Lossless Ethernet is used instead of normal Ethernet with Converged Enhanced Ethernet (CEE) or Data Center Bridging (DCB) or Data Center Ethernet

(DCE).

Layer structure of FCoE with encapsulation and CEE layers

Layer structure of FCoE with encapsulation and CEE layers

The FC layer model is modified accordingly. The FC-0 and FC-1 layers are replaced by the lower Ethernet layers, and the encapsulation layer is inserted between the layers for the FC services. The lower layers are extended to the Converged Enhanced Ethernet. For lossless transmission, IEEE is developing four protocols that govern the flow of data and their priorities. The IEEE 802.1Qbb working group

isworking on Priority Flow Control

(PFC), 802.1Qaz is workingon Enhanced Transmission Selection (ETS) and Data Center Bridging Exchange Protocol (DCBX), and 802.1Qau is working on Quantized Congestion Notification

(QCN). Behind FCoE are Brocade, Cisco, EMC, Emulex, IBM, Intel, Nuova, QLogic, and Sun, who have submitted their specifications for "Fiber Channel over Ethernet" to ANSI's T11 committee.

To ensure the reliability required in storage networks, another proposal went to IEEE that addresses the unreliability of the IP protocol, which can lose data packets.

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Englisch: fibre channel over Ethernet - FCoE
Updated at: 01.09.2011
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