FCoE Initialization Protocol
The FCoE Initialization Protocol (FIP) is defined by the T11 FC-BB-5 standard as the control plane component of the FCoE protocol. The FCoE protocol is the other component from that standard, and it is defined as the data plane. This means that FIP is responsible for exchanging the needed information, performing the needed negotiations, and maintaining the information exchange between the connected devices in order to create and maintain an environment that allows the operation of the FCoE protocol (in other words, it allows the exchange of FCoE Ethernet frames).
The FCF and the end node are capable of differentiating between the FIP and the FCoE communication based on the Ethertype value. The FIP Ethertype value is 0x8914.
The FIP sequence of operations, shown in Figure 15-9, is as follows:
Figure 15-9 FIP Operation
FIP VLAN discovery: The FCoE VLAN used by all other FIP protocols and the FCoE communication is discovered. The FIP uses the native VLAN to discover the FCoE VLAN. The FIP VLAN discovery protocol is the only FIP running on the native VLAN. The rest of the FIP and FCoE communication happens in the discovered FCoE VLANs.
FIP FCF discovery: When an FCoE-capable device is connected to the network, it announces itself by sending a Discovery Solicitation Message. The Ethertype in these frames is set to 0x8914 to indicate this is an FIP communication. If it’s connected to an FCF, it receives the discovery message and responds with a solicited advertisement. In the response message is the FCF FC-MAP value. The Ethertype is still FIP.
FCoE virtual link instantiation: The FIP carries the needed fabric login (FLOGI), fabric discovery (FDISC), and logout (LOGO). The result is that the VFC port is assigned an FCID and a MAC address for the subsequent FCoE communication. The Ethertype is still FIP.
FCoE virtual link maintenance: After the previous step, all the needed information has been exchanged between the devices and the needed negotiations have taken place. The devices can communicate using the FCoE protocol to carry FC frames. Therefore, the FCoE protocol is operating at this stage. In the meantime, the FIP continues to regularly exchange control information between the devices to maintain the virtual link between the VN and the VF ports. The Ethertype is FCoE.
During the first stage of the process, the devices communicate with each other with the goal of the CNA reporting that it is FCoE capable and finding the FCoE VLAN, which is used by the FIP. This happens as the CNA, using the Ethernet burnt-in address (BIA) as a source MAC address, sends a solicitation to the All-FCF-MACs multicast address to which all the FCFs listen. The Ethertype of the multicast solicitation frame is set to the FIP value of 0x8914.
This communication happens in the native VLAN, and the FIP VLAN discovery is the only stage that happens in it. The subsequent communication of the FIP takes place in the FCoE VLAN used by the chosen FCF.
In the FC-BB-5 standard, the FIP VLAN discovery protocol is described as optional. This means that if it is not used, the FCoE VLAN will default to VLAN 1002, and it might not be the FCoE VLAN used by the Unified Fabric. That’s why Cisco strongly recommends that the FIP VLAN discovery protocol be used.
Once the FCoE VLAN discovery finishes by providing information for the FCoE VLAN, it then starts the next stage, where the FIP FCF discovery protocol takes place. It uses the FCoE VLANs, and the goal is to find the FCFs and to start negotiations with them. For this purpose, the CNA sends a multicast solicitation, the ALL-ENode-MACs multicast MAC address. This message will identify the VF-Port-Capable FCF MACs. One such multicast solicitation will be sent to each of the FCoE VLANs discovered in the previous phase.
Upon receiving the multicast solicitation frame, the FCF will respond with a unicast advertisement. It will contain the first 24 bits of the FPMA; this is the FC-MAP value configured on the FCF. The other information contained in the FCF advertisement is as follows:
- FIP timeout values
- FCF priority
- Fabric name (the WWNN of the fabric)
- FCF MAC address
- Switch name
- Switch capabilities
Based on that information, the CAN will decide which FCF to communicate with. For this decision, the CAN considers the FCF priority and the FCF MAS address.
The third phase will be to establish the virtual link between the VN and the VF port. The ENode, or the host, will send FLOGI frames to the FCID of FF:FF:FE. This is a well-known address for the fabric login communication. The Ethertype of the FCoE frames will still be FIP.
The FCF will assign an FCID for the host and will respond to the FLOGI request. With this, an FPMA MAC address will be created for the subsequent FCoE communication, and the virtual link will be established.
This concludes the work of the FIP for negotiating and establishing the environment for the FCoE communication. The subsequent frames will have the FCoE Ethertype. The FIP will continue to communicate in the background with the goal of maintaining the virtual link.