The FCoE standard defines two types of endpoints: FCoE Ethernet Nodes (ENodes) and Fibre Channel Forwarders (FCFs). Figure 9-10 shows a simplified version of an ENode. An ENode (also called a CNA adapter) is a Fibre Channel HBA implemented within an Ethernet NIC. The data-forwarding component that handles FC frame encapsulation/decapsulation is called an FCoE Link EndPoint (LEP). An FCoE LEP is a virtual FC interface mapped onto the physical Ethernet interface. An FCoE controller is the functional entity that performs the FIP and instantiates VN_Port/FCoE_LEP pairs. We discuss the FCoE Initialization Protocol (FIP) in the next section.
Figure 9-10 Simplified ENode
Note
Only second-generation CNAs support the FCoE control plane protocol called FIP. FIP support is required to build certain types of topologies in FCoE; for example, use of FEXs in the FCoE topology requires FIP support.
Figure 9-11 shows a simplified version of the FCoE switch. FCF is the forwarding entity inside an FCoE switch. An FCF switch is one that actually contains both a Fibre Channel switch and an Ethernet switch—for example, the Cisco Nexus 5000 Series switch. A Cisco MDS switch with FCoE module installed can act as an FCF switch also. The FCF processes the Fibre Channel logins and consumes one domain ID. FCF performs the encapsulation and decapsulation of the FCoE frames and forwards the FCoE traffic based on Fibre Channel information that the frames contain.
Figure 9-11 Simplified FCoE Switch
ENodes present virtual FC interfaces in the form of VN_Ports, which can establish FCoE virtual links with FCFs’ VF_Ports, as shown in Figure 9-12. FCFs present virtual FC interfaces in the form of VF_Ports or VE_Ports; a VF_Port establishes FCoE virtual links with a CNA’s VN_Port or FCoE NPV’s VNP_Port, and VE_Ports enable FCFs to establish FCoE virtual links with other FCFs. These interface types have their equivalents in native Fibre Channel’s N_Ports, F_Ports, and E_Ports. A virtual fabric (VF) port in an FCoE network acts as a fabric port that connects to a peripheral device (host or disk) operating as a VN_port. A VF_port can be attached to only one VN_port. A virtual expansion (VE) port acts as an expansion port in an FCoE network and can connect to multiple FCoE switches together in the network.