Fibre Channel over Ethernet

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Fibre Channel over Ethernet (FCoE) is a proposed mapping of Fibre Channel frames over selected full duplex IEEE 802.3 networks. This allows Fibre Channel to leverage 10 Gigabit Ethernet networks while preserving the Fibre Channel protocol. The specification is supported by a large number of network and storage vendors, including BLADE Network Technologies, Broadcom, Brocade, Cisco, EMC, Emulex, Finisar, HP, IBM, Intel, Mellanox, Netapp, Nuova, Qlogic and Sun Microsystems.

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[edit] Functionality

FCoE essentially maps Fibre Channel natively over Ethernet while being independent of the Ethernet forwarding scheme. The FCoE protocol specification replaces the FC0 and FC1 layers of the Fibre Channel stack with Ethernet. By retaining the native fibre channel constructs, FCoE allows a seamless integration with existing Fibre Channel networks and management software.

In today's data centers which use Ethernet for TCP/IP networks and Fibre Channel for storage area networks (SANs), with FCoE, Fibre Channel becomes another network protocol running on Ethernet, alongside traditional Internet Protocol (IP) traffic. This means FCoE runs alongside IP on Ethernet, unlike iSCSI which runs on top of IP using TCP. As FCoE does not use IP (Layer 3), it is not routable at the IP layer, and will not work across routed IP networks.

Since classical Ethernet is lossy, unlike Fibre Channel, to create a loss-less Ethernet required modifications to Ethernet which are being driven through the standards.

Enabling FCoE required 3 specific modifications to Ethernet in order to deliver the capabilities of Fibre Channel in SANs. This includes

  • Encapsulation of a native fibre channel frame into an Ethernet Frame
  • Extensions to the Ethernet protocol itself to enable a lossless ethernet fabric
  • Replacing the fibre channel link with MAC addresses in a lossless Ethernet

Computers using FCoE use a Converged Network Adapter (CNA), which is both a Fibre Channel Host Bus Adapter (HBA) and an Ethernet Network Interface Card (NIC) to the server, but appears as a single Ethernet NIC to the network. Converged Network Adapters essentially provide an evolutionary approach to consolidation of a server's I/O over a single network (Ethernet) reducing network complexity in the Data Center.

[edit] Application

The main application for FCoE is in the data centers.

FCoE is particularly useful for dense rack-mounted and blade servers in the data centers where cable simplification is the key requirement as well as for server virtualization which often requires many I/O connections per server.

With FCoE, network (IP) and storage (SAN) data traffic can essentially be consolidated with a single switch. Further, with the ability to combine Fibre Channel with 10 Gigabit Ethernet (GbE), companies can consolidate I/O, called unified I/O. This multifold consolidation

  • reduced the number of network interface cards required to connect to disparate storage and IP networks
  • reduces the number of cables and adapters,
  • reduces the overall power and cooling costs
  • increased utilization of the servers through server virtualization technologies

[edit] Frame Format

FCoE is encapsulated over Ethernet with the use of a dedicated Ethertype, 0x8906. A single 4-bit field (version) satisfies the IEEE sub-type requirements. The other bits in the frame specifically, the source mac address, destination mac address, VLAN tags, SOF and EOF are all encoded as specified in RFC 3643. Reserved bits are present to guarantee that the FCoE frame meets the minimum length requirement of Ethernet. Inside the encapuslated Fibre Channel frame, the frame header is retained so as to allow connecting to a storage network by passing on the Fibre Channel frame directly after de-encapsulation.

The FIP (FCoE Initialization Protocol) is also currently being defined.

FCoE Frame Format

[edit] Timeline

The project has been proposed in the T11 standard body. of the American National Standards Institute (ANSI) in April 2007 and a draft of the standard is expected in June 2008.

[edit] See also

[edit] External links

The project's homepage is http://www.t11.org/fcoe.

Development page of Fibre Channel over Ethernet implementation for the Linux operating system http://www.open-fcoe.org/.

Fibre Channel Industry Association (FCIA) paper on FCoE http://www.fibrechannel.org/OVERVIEW/FCIA_SNW_FCoE_WP_Final.pdf

A site that tracks FCoE development http://www.fcoe.com.

[edit] News Articles

Byte & Switch coverage for FCIA announcements http://www.byteandswitch.com/document.asp?doc_id=145756&WT.svl=wire2_6