The Napkin Dialogues: FCoE vs. QCN
While at Cisco Live I had the pleasure of meeting several people who were curious about Multihop FCoE but had the unfortunate experience of getting too much misinformation from several sources (yes, including some of Cisco’s competition, but even some partners!). Some had already seen my article on FCoE and TRILL and wanted to know if I could help explain the relationship between FCoE and QCN (Quantized Congestion Notification), one of the documents in the IEEE DCB standard revision.
Even though we have a very good, short white paper on the subject, this is one of those subjects that as soon as people ask about it we break out the white boarding, or in the case of being at Cisco Live, the napkins. There are just some things that pictures help explain better.
Because of this, I’m going to try something different with this blog. It may work, or I may fall flat on my face; I suppose we shall find out.
Thing is, when I tried to write down this blog in the form of a conversation – because it seems people are liking that format – the blog grew longer and longer as I tried to explain these concepts in plain English. Creating the accompanying drawings made it even longer, so I’m going to jump in with both feet and try something radically different, something I haven’t seen in a technical blog before. As always, your mileage may vary.
So, without further ado…
Update: I would like to thank Erik Smith of EMC for pointing out that an earlier version of this blog had a pretty significant inaccuracy. In my attempt to simplify the process for the sake of writing this blog, I unintentionally conflated some of the FC operations and, well, no other way to say it. What I wrote was wrong (I hate being wrong! Especially in public!). I’ve since changed the graphics to represent the correct technology and hopefully have eliminated potential sources of confusion. – J