Blog on June 25, 2010
At the latest meeting of the T11.3 standards organization (FC-BB-6 Ad Hoc Working Group) the concept of FCoE Direct End-to-End protocol was accepted for input into the Workgroup's next standard. It is also known as FCoE VN_Port to VN_Port (FCoE VN2VN). This new function permits FCoE adapters, which are interconnected within the same Level 2 Lossless Ethernet network, to discover and connect to compatible FCoE adapters -- which have the appropriate Virtual N_Ports -- and then transmit Fibre Channel commands and data via the standard FCoE protocol.
This is all done on a Lossless Ethernet Network without any assistance from a Fibre Channel Switch or an FCoE Switch (called an FC Forwarder -- FCF). All that is needed is the appropriate VN2VN FCoE Adapters and a Lossless Ethernet layer 2 Network.
There also exists, today, some Open Source FCoE software that only requires a normal Ethernet NIC, to operate standard FCoE protocols (a special Converged Network Adapter -- CNA -- is not required). It is expected that this Open Source software will be updated to also support the new VN2VN function.
The VN2VN (direct End-to-End) function will support 2 types of direct connections:
1. Connections through Lossless Ethernet switches
2. One to One Connection via a single cable (point to point)
The FCoE protocol is made up of 2 types of Ethernet frames (which have their own unique Ethertypes):
1. The FCoE initialization Protocol (FIP) frame packets
2. The Fibre Channel over Ethernet (FCoE) frame packets
The FIP packets are only used as part of discovery and connection setup whereas the FCoE packets carry the actual FC commands and data. The new VN2VN functions have only added additional FIP packets, and have left the rest of the protocol unchanged. The new VN2VN FIP packets were needed since in this mode there is no FCF to provide connection services.
The transfer of FC data and commands via the FCoE protocol -- which was developed in the T11.3 standards organization (FC-BB-5 Ad Hoc Working Group) -- continues to operate as currently specified and will continue unchanged in this new VN2VN environment.
The upper levels of the protocol remain FC, and that means that there continues to be complete compatibility with existing FC & FCoE Device Drivers etc. The vendors are, of course, adding additional management capabilities to exploit the additional capabilities of FCoE, but the command and data protocol do not require any modifications. Likewise, as adapters are updated to support VN2VN mode, the upper layers will retain their current FC compatibility even as additional management capabilities are added to permit ease (and flexibility) of use.
This new VN2VN capability will permit FC protocol to go "Down Market" to entry and Mid Range environments. Yet, as the installation grows it will be able to install FCF switches and thereby obtain the additional functions of a FC network without having to change the server or storage connections.
The new VN2VN capability will be competitive to iSCSI within a Data Center Environment. And I fully expect the Lossless Ethernet Standards, which were focused at a 10Gb/s Ethernet, to be offered by various vendors on 1Gb/s networks and switches. This will mean that FCoE VN2VN will operate very well with the Open Source FCoE code and 1Gb/s NICs without the overhead of TCP/IP. This should make the FCoE VN2VN capability very performance competitive with iSCSI.
Stay tuned to this Blog to see how the capability unfolds.
