Ethernet Fabric (VDX, CNA)

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Brocadian
Posts: 23
Registered: ‎04-06-2009

FCoE <> Interoperability

Throughout this week at SNW, I've been talking to people about FCoE, and one comment has been made over and over.  There seems to be a misconception that FCoE is the grand unifier of Fibre Channel fabrics.  The thought is that somehow FCoE will allow Fabric Brand B ()and Fabric Brand Z to interoperate in a way not supported in Fibre Channel.

That is not the case.  Since FCoE is an encapsulation protocol, the stuff that goes into FCoE frames is precisely the Fibre Channel content that would have otherwise gone directly over the link.  That means that Fabric Brand B frames now look like Fabric Brand B frames in an FCoE wrapper.  There is no more interoperability than before - just a common wrapper on the outside.

Although this may seem obvious, the manifestation of the misunderstanding takes place more subtly.  Suppose that the Data Center uses Brand B for their Fibre Channel and Brand Z for their Ethernet switch provider.  The networking people decide to upgrade their Brand Z equipment, and so when they purchase it, they buy Ethernet equipment from Vendor Z with upgraded hardware and licenses to be "FCoE Ready".

Uh-oh.  At the FCoE layer, there will be no more support for interoperability between Brand B and Brand Z than there is today.  In other words, the investment in Vendor Z's "FCoE ready" enhancements will be lost.  I've been in meetings where, when this fact surfaces, the Ethernet and Fibre Channel people just look at each other, realizing that scarce funds have just been wasted on features that will never be used.

The moral of the story is that the Fiber Channel and Ethernet architects need to get in the same room, and if the Ethernet teams are going to upgrade, they need to do so in a way that will be sure that today's limited funds will not be spent on licenses, features, and hardware that will not realize any real value as FCoE is rolled into the Data Center.

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