What Is Fibre Channel over Ethernet (FCoE)?

Intro: Have you ever heard FCoE before? It is a storage protocol that ensures the direct transmission of Fibre Channel communications over Ethernet. Refer here for more details about FCoE.

Definition

FCoE, short for Fibre Channel over Ethernet, is a computer network technology, which encapsulates Fibre Channel frames over Ethernet. It enables Fibre Channel to use 10 Gigabit Ethernet networks or higher speeds while retaining the Fibre Channel protocol.

FCoE transforms Fibre Channel traffic into existing high-speed Ethernet infrastructures and then converges IP protocols and storage into a single cable transmission and interface.

Functionality

FCoE transmits Fibre Channel directly over Ethernet, But independent of the Ethernet forwarding scheme. The FCoE protocol specification uses Ethernet to replace the FC0 and FC1 layers of the Fibre Channel stack. FCoE is designed to integrate with the existing Fibre Channel networks and management software by retaining the fibre channel structures.

Data centres use Fibre Channel for storage area networks (SANs) and Ethernet for TCP/IP networks. Fibre, with the FCoE channel, becomes another network protocol running on Ethernet and traditional Internet protocol (IP) traffic.

Unlike iSCSI, which operates on top of TCP and IP, FCoE runs directly over Ethernet in the network protocol stack.

Unlike Fibre Channel, traditional Ethernet does not have priority-based flow control, so FCoE needs to strengthen Ethernet standards to support priority-based flow control mechanisms to reduce frame loss due to congestion. The IEEE standards agency has increased its priority in the data centre bridge (dcb) Task Group.

Fibre Channel needs three significant extensions to provide the capabilities of Fibre Channel over Ethernet networks:

• Encapsulation of native Fibre Channel frames to Ethernet frames.
• Extensions to the Ethernet protocol enable an Ethernet fabric that does not frequently lose frames during congestion.
• The mapping exists between Fibre Channel N_port IDs (FCIDs) and Ethernet MAC addresses.

Computers can connect to FCoE using a converged network adapter (CNA), which contains Fibre Channel host bus adapter (HBA) and Ethernet network interface controller (NIC) features on the same physical card.

Application

The primary application of FCoE is in data centre SANs(storage area networks ). Because of cabling reduction, FCoE has a particular application in the data centre and makes it possible for server virtualization applications, which typically require many physical I/O connections per server.

With FCoE, users can use a single network to consolidate network (IP) storage (SAN) data traffic. Here are the benefits of this consolidation:

• reduce cooling costs and power
• reduce the number of switches and cables
• reduce the number of network interface cards for connecting to disparate storage and IP networks

Frame Format

FCoE is just the encapsulation of FC frames in Ethernet frames. There is a one-to-one relationship between FC and Ethernet frames. Thus, FC frames are never sent across multiple Ethernet frames and in segments.

The maximum size of an FCoE frame reaches 2180bytes. The network must support up to 2.5KB of MTU, also known as baby jumbo frames, to accommodate this.

Port Types

FCoE offers additional port types for standard FC.

• VN_Port: Virtual Node port is instantiated by the ENode and is synonymous with the N_Port in Fibre Channel.
• VF_Port: Virtual Fabric port is instantiated by the FCF and is synonymous to the F_Port in Fibre Channel.
• VE_Port: Virtual Ethernet port is instantiated by the FCF and is synonymous with the E_Port in Fibre Channel.

Advantages

• ImprovedFibre Channel is a high-speed storage protocol, and some storage devices support speeds of up to 128 Gbps. Even so, such devices are often expensive. Therefore, many organizations still use 8 Gbps storage devices and SANs. FCoE enables such organizations to achieve higher speeds by using comparatively inexpensive Ethernet networks.
• Reduce complexity. Storage-related traffic is sent over a conventional Ethernet network, so it doesn’t need Fibre Channel switches. In turn, it reduces both the architectural complexity and costs.
• Simplify network management. There are countless tools for monitoring and managing Ethernet networks.FCoE routes storage traffic over a standard Ethernet network, so organizations might use their existing networking tools to manage storage traffic.