FCoE and the Return of Spanning Tree

One of the most amusing parts about Fibre Channel over Ethernet(FCoE) is that Spanning Tree is making a triumphant comeback. And I am talking a Roman style parade after the gates to the city have been built and lined with gold.

The IEEE is working on a standard 802.1AQ named Shortest Path Bridging and described as an ‘incremental’ advance on Multiple Spanning Tree Protocol. Well, if you do a bit of reading, ‘incremental’ means it uses IS-IS to locate Layer 2 paths through the network using CLNS (yes, those of us old enough to remember GOSIP and OSI protocols are having conniptions….).

I love the metaphor that ‘incremental’ means adding a fully fledged routing protocol supporting spanning tree to determine layer 2 paths through the network.

Oh how we laughed.

IS-IS is a good protocol, and runs some of the largest Service Provider backbones in the world. There have been many improvements in the last five years that bring IS-IS into mainstream. The idea of extending CLNS to carry Layer 2 path information is conceptually a great idea.

But very very hard to sell.

Oh how I laughed.

You see, I had a meeting recently with the storage people and they instantly had apoplexy. “My goodness, Layer 2 spanning tree!” We cannot allow that.

Of course, they seem to have forgotten that FC is a Layer 2 protocol, and that is why it doesn’t scale….but enough about that for now.

And then the Managers got wind of this. If there is anything that strikes fear into the the heart of a Data Centre manager, Spanning Tree is it. It seems to me that the least seven or eight years has seen constant innovation to remove Spanning Tree. And now I am proposing bringing it back !

Oh how we laughed.

The standards track from the IEEE is continuing on, and they expect the 802.1Qbb, 802.1Qau, 802.1Qaz and 802.1aq standards to be complete sometime in 2010. What ? 2010 for the standards only !

Oh how we laughed.

There is an awful lot of noise about FCoE, but it really faces some huge challenges before its is going to get onto many roadmaps. Even though Cisco is pushing it along like Drott-D9 bulldozer and making enormous promises, I can’t get my fellow workers to stop laughing.

Oh dear, how we laughed.

About the author

Greg Ferro

Greg Ferro is the co-host of Packet Pushers. After surviving 25 years in Enterprise IT with only minor damage, he uses his networking expertise for good in the service of others by deep diving on technology and industry. His unique role as an inspirational cynicist brings a sense of fun, practicality and sheer talent to world of data networking and its place in a world of clouds.

He blogs regularly at http://etherealmind.com and the podcasts are at http://packetpushers.net.

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