Brocade Network OS Administrator’s Guide v4.1.1 - Manual (Page 338)

FCoE terminology TABLE 57
Term Description
FCoE Fibre Channel over Ethernet
DCB Data Center Bridging
VN_Port FCoE equivalent of an FC N_Port
VF_Port FCoE equivalent of an FC F_Port
ENode An FCoE device that supports FCoE VN_Ports (servers and target devices)
End-to-end FCoE
The Brocade VCS Fabric is a convergence-ready fabric. This means it is capable of providing lossless
service and other features expected of a CEE-capable network. This includes support for multi-hop
FCoE, where an FCoE initiator can communicate with an FCoE target that is a number of hops away.
FCoE operations
Each switch in the Brocade VCS Fabric cluster acts as a fully functional FCoE Forwarder (FCF). All
Fibre Channel (FC) services required to support a Virtual Network (VN) must run on every Brocade
VCS Fabric cluster switch, and each switch in the fabric acts as if it were a separate domain in an FC
SAN.
For all practical purposes, a Brocade VCS Fabric operates similarly to an FC fabric because all the
FCoE initiators and targets are connected to the Brocade VCS Fabric. Each switch in the cluster gets
a domain ID, and once the fabric forms, all the FC services (such as Name Server, Login Controller,
Domain Controller) are available on each individual cluster switch.
Network OS 4.0.0 and later supports FCR/LSAN zoning. A combination of 2000 FCoE devices and
1000 FC routed devices (for a total maximum of 3000 devices) is the fabric limit. Because open zoning
floods all the State Change Notifications (SCNs) to every device, it should be used only when the
fabric has 300 total devices or fewer. Fabrics with higher device counts should have user-defined
zoning configurations, with a maximum of 255 devices per zone.
FCoE traffic forwarding across the fabric follows the same equal-cost multi-path (ECMP) routing rules
as does LAN traffic forwarding.
FCoE end-to-end forwarding
FCoE frame forwarding between two FCoE devices attached to the Brocade VCS Fabric works
similarly to Layer 3 IP routing. The end-node talks to the default gateway’s MAC address and the
Layer 2 headers are modified hop-by-hop until the frame reaches its final destination. Forwarding
decisions are based on the contents of the IP header in the case of IP routing, and the IP header is
untouched along the path. FCoE forwarding works the same way.
The following figure illustrates this process. Assume that VN1 (an FCoE initiator) is trying to access
VN2 (an FCoE target).
1. VN1 and VN2 discover VF1 and VF2 through FIP Discovery Protocol and perform a Fabric Login
(FLOGI) to their respective VF ports. That is, VN1 performs an FIP FLOGI to VF1 and VN2
performs a FIP FLOGI to VF2. This works like IP in that all communication between the end-station
End-to-end FCoE
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