Comments on: FCoE and the Return of Spanning Tree http://etherealmind.com/fcoe-forces-return-spanning-tree/ Network design, architecture, thinking, working. Tech. Wed, 23 May 2012 00:26:00 +0000 hourly 1 http://wordpress.org/?v=3.3.2 By: Bob http://etherealmind.com/fcoe-forces-return-spanning-tree/#comment-914 Bob Mon, 29 Mar 2010 17:49:40 +0000 http://etherealmind.com/?p=1404#comment-914 Your comment "You see, I had a meet≠ing recently with the stor≠age people and they instantly had apo≠plexy. ìMy good≠ness, Layer 2 span≠ning tree!î We can≠not allow that. Of course, they seem to have for≠got≠ten that FC is a Layer 2 pro≠tocol, and that is why it doesnít scale.Öbut enough about that for now." is way off the mark. You seem to be hinting or insinuating that the storage guys are unaware of the fact that FC is an L2 protocol. They (we) are well aware of that fact, but we also don't suffer from loops the way Ethernet does. All L2 protocols are not created equal. Just different. FC doesn't loop. FC does multiple paths. FC scales, just differently than Ethernet. Your comment “You see, I had a meet≠ing recently with the stor≠age people and they instantly had apo≠plexy. ìMy good≠ness, Layer 2 span≠ning tree!î We can≠not allow that.

Of course, they seem to have for≠got≠ten that FC is a Layer 2 pro≠tocol, and that is why it doesnít scale.Öbut enough about that for now.” is way off the mark. You seem to be hinting or insinuating that the storage guys are unaware of the fact that FC is an L2 protocol. They (we) are well aware of that fact, but we also don’t suffer from loops the way Ethernet does. All L2 protocols are not created equal. Just different. FC doesn’t loop. FC does multiple paths. FC scales, just differently than Ethernet.

]]> By: Greg Ferro http://etherealmind.com/fcoe-forces-return-spanning-tree/#comment-913 Greg Ferro Fri, 27 Mar 2009 18:29:09 +0000 http://etherealmind.com/?p=1404#comment-913 My case would be that Ethernet is completely imperfect and no amount of fudging would fix it. Ethernet is the lowest and least LAN technology created in the last thirty years. However, we, the world, chose it over others. Perpetuating it is a disappointment, and I would prefer that IP was used for everything and spanning tree would not be required. That is, Ethernet is a locally significant technology only (see IPv6 local scope). It is not suitable for building a data centre fabric. My case would be that Ethernet is completely imperfect and no amount of fudging would fix it. Ethernet is the lowest and least LAN technology created in the last thirty years.

However, we, the world, chose it over others. Perpetuating it is a disappointment, and I would prefer that IP was used for everything and spanning tree would not be required. That is, Ethernet is a locally significant technology only (see IPv6 local scope).

It is not suitable for building a data centre fabric.

]]> By: Stuart Miniman http://etherealmind.com/fcoe-forces-return-spanning-tree/#comment-912 Stuart Miniman Fri, 27 Mar 2009 18:20:50 +0000 http://etherealmind.com/?p=1404#comment-912 Greg, You focused on the IEEE L2MP activity, but what about IETF TRILL? Radia Perlman, the inventor of spanning tree is an active participant in these updates, surely you don't think that Ethernet as deployed today is perfect? Greg,
You focused on the IEEE L2MP activity, but what about IETF TRILL? Radia Perlman, the inventor of spanning tree is an active participant in these updates, surely you don’t think that Ethernet as deployed today is perfect?

]]> By: Dirk-Jan van Helmond http://etherealmind.com/fcoe-forces-return-spanning-tree/#comment-911 Dirk-Jan van Helmond Wed, 18 Mar 2009 08:23:21 +0000 http://etherealmind.com/?p=1404#comment-911 Ah, millisecond IS-IS convergence is an interesting question that I unfortunately can't answer. According to this PDF, the IEEE is still out on that. http://www.ieee802.org/1/wp-content/uploads/public/docs2008/aq-fedyk-SPB-status-update-1108-v1.pdf Ah, millisecond IS-IS convergence is an interesting question that I unfortunately can’t answer.

According to this PDF, the IEEE is still out on that.
http://www.ieee802.org/1/wp-content/uploads/public/docs2008/aq-fedyk-SPB-status-update-1108-v1.pdf

]]> By: Greg Ferro http://etherealmind.com/fcoe-forces-return-spanning-tree/#comment-910 Greg Ferro Tue, 17 Mar 2009 19:12:50 +0000 http://etherealmind.com/?p=1404#comment-910 Does this mean that L2 SPF will replace STP then ? Have I misunderstood the fundamental purpose of 8021.AQ ? Also, how does IS-IS converge in milliseconds ? Won't that be a requirement in DCB ? Does this mean that L2 SPF will replace STP then ? Have I misunderstood the fundamental purpose of 8021.AQ ?

Also, how does IS-IS converge in milliseconds ? Won’t that be a requirement in DCB ?

]]> By: Dirk-Jan van Helmond http://etherealmind.com/fcoe-forces-return-spanning-tree/#comment-909 Dirk-Jan van Helmond Tue, 17 Mar 2009 15:38:07 +0000 http://etherealmind.com/?p=1404#comment-909 By the way, we are on the brink of completely getting rid of spanning-tree. Nortel ofcourse has SMLT and are developing hard on PLSB, which is a combination of mac-in-mac and 'l2-isis'. L2 isis is tightly coupled to L2 multipathing. Woven is releasing L2MP products, Cisco has VSS and vPC, which is a first step to L2MP, and that is roadmapped for the Nexus platform. Therefore I do believe that l2-isis or L2MP or 802.1AQ is the way to go. By the way, we are on the brink of completely getting rid of spanning-tree.

Nortel ofcourse has SMLT and are developing hard on PLSB, which is a combination of mac-in-mac and ‘l2-isis’. L2 isis is tightly coupled to L2 multipathing. Woven is releasing L2MP products, Cisco has VSS and vPC, which is a first step to L2MP, and that is roadmapped for the Nexus platform.

Therefore I do believe that l2-isis or L2MP or 802.1AQ is the way to go.

]]> By: Dirk-Jan van Helmond http://etherealmind.com/fcoe-forces-return-spanning-tree/#comment-908 Dirk-Jan van Helmond Tue, 17 Mar 2009 15:30:13 +0000 http://etherealmind.com/?p=1404#comment-908 I believe that FCoE has a future in the datacenter, but I am in no way an FCoE evangelist. And I think you are misconstruing things. Both STP and SPF algorithms are used to create a loop-free topology. The difference between these is that STP and deriviates create a single (or in case of MSTP of PVST some) spanning-trees that all nodes must abide by. This does not ensure the best path for every node in the tree. SFP creates a shortest path tree per node, which DOES ensure a best path for every node. Besides that, path learning for 802.1d is done by flooding of frames and closing interfaces, which in no way scales, while 802.1AQ used link-state updates, that does scale and makes Layer 2 multipathing possible. I believe that FCoE has a future in the datacenter, but I am in no way an FCoE evangelist.

And I think you are misconstruing things. Both STP and SPF algorithms are used to create a loop-free topology. The difference between these is that STP and deriviates create a single (or in case of MSTP of PVST some) spanning-trees that all nodes must abide by. This does not ensure the best path for every node in the tree. SFP creates a shortest path tree per node, which DOES ensure a best path for every node.

Besides that, path learning for 802.1d is done by flooding of frames and closing interfaces, which in no way scales, while 802.1AQ used link-state updates, that does scale and makes Layer 2 multipathing possible.

]]> By: Ivan Pepelnjak http://etherealmind.com/fcoe-forces-return-spanning-tree/#comment-907 Ivan Pepelnjak Sat, 14 Mar 2009 19:16:32 +0000 http://etherealmind.com/?p=1404#comment-907 You forgot to mention the good old days (around 15 years ago) when someone had a great idea to run SPF on MAC addresses and call the chimera "brouter". Those were the days when a "switch" was not a networking term, "bridge" was a four-letter-word and "router" was the hero-of-the-day, so those that were not competent enough to program a router tried to repaint a bridge. It's so funny to see the same idea reappear, this time using IS-IS as the SPF (obviously we've progressed a long way standard-wise in the last 15 years :). You forgot to mention the good old days (around 15 years ago) when someone had a great idea to run SPF on MAC addresses and call the chimera “brouter”. Those were the days when a “switch” was not a networking term, “bridge” was a four-letter-word and “router” was the hero-of-the-day, so those that were not competent enough to program a router tried to repaint a bridge.

It’s so funny to see the same idea reappear, this time using IS-IS as the SPF (obviously we’ve progressed a long way standard-wise in the last 15 years :) .

]]> By: Dmitri http://etherealmind.com/fcoe-forces-return-spanning-tree/#comment-906 Dmitri Sat, 14 Mar 2009 10:32:37 +0000 http://etherealmind.com/?p=1404#comment-906 Greg, if I'm not mistaken, FC had always had a routing protocol built into it, FSPF. Also, your statement about 7 years of innovation to remove spanning tree puzzled me. I admit I am not so close to the happenings in the DC arena, but I have been doing Carrier Ethernet for these last 7 years and have not noticed much in the department of removing STP. Yes, where possible, LAG/LACP is used, but what else? (I'm not talking about PBB or MPLS, as I would have thought they are not directly usable for the DC internal LANs). Greg, if I’m not mistaken, FC had always had a routing protocol built into it, FSPF.

Also, your statement about 7 years of innovation to remove spanning tree puzzled me. I admit I am not so close to the happenings in the DC arena, but I have been doing Carrier Ethernet for these last 7 years and have not noticed much in the department of removing STP. Yes, where possible, LAG/LACP is used, but what else? (I’m not talking about PBB or MPLS, as I would have thought they are not directly usable for the DC internal LANs).

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