Category: FCoE

A tweet from J Michel Metz has alerted me to a “Why TRILL won't work for data center network architecture” article by Anjan Venkatramani, Juniper’s VP of Product Management. Most of the long article could be condensed in two short sentences my readers are very familiar about: Bridging does not scale and TRILL does not solve the traffic trombone issues (hidden implication: QFabric will solve all your problems)... but the author couldn’t resist throwing “FCoE over TRILL” bone into the mix.

Intel announced its Open FCoE (software implementation of FCoE stack on top of Intel’s 10GB Ethernet adapters) using the cloudy bullshit bingo including simplifying the Data Center, Free New Technology, Cloud Vision and Green Computing (ok, they used Environmental impact) and lots of positive supporting quotes. The only thing missing was an enthusiastic Gartner quote (or maybe they were too expensive?).

Was anyone trying to sell you the “wonderful” idea of running FCoE between Data Centers instead of FC-over-DWDM or FCIP? Sounds great ... until you figure out it won’t work. Ever ... or at least until switch vendors drastically increase interface buffers on the 10GE ports.

FCoE requires lossless Ethernet between its “routers” (Fiber Channel Forwarders – see Multihop FCoE 101 for more details), which can only be provided with Data Center Bridging (DCB) standards, specifically Priority Flow Control (PFC). However, if you want to have lossless Ethernet between two points, every layer-2 (or higher) device in the path has to support DCB, which probably rules out any existing layer-2+ solution (including Carrier Ethernet, pseudowires, VPLS or OTV). The only option is thus bridging over dark fiber or a DWDM wavelength.

Just when I hoped we were finally getting somewhere with the FCoE/QCN discussion, Brocade managed to muddy the waters with its we-still-don’t-know-what-it-is announcement. Not surprisingly, networking consultants like my friend Greg Ferro of the Etherealmind fame responded to the shenanigan with statements like “FCoE ... is a technology so mindboggingly complicated that marketing people can argue over competing claims and all be correct.” Not true, the whole thing is exceedingly simple once you understand the architecture (and the marketing people always had competing claims).

Pretend for a minute that FC ≈ IP and LAN bridging ≈ Frame Relay, teleport into this parallel universe and allow me to tell you the whole story once again in more familiar terms.

One of the recurring religious FCoE-related debates of the last months is undoubtedly “do you need QCN to run FCoE” with Cisco adamantly claiming you don’t (hint: Nexus doesn’t support it) and HP claiming you do (hint: their switch software lacks FC stack) ... and then there’s this recent announcement from Brocade (more about it in a future post). As is usually the case, Cisco and HP are both right ... depending on how you design your multi-hop FCoE network.

It looks like everyone (and their dog) is writing about DCB and FCoE these days, but occasionally we get a fresh thought: Ron Fuller compares FC/Ethernet to East/West coast mentality. Great analogy ;)

“Use FC where you feel you need to, use Ethernet (NFS, CIFS, iSCSI) everywhere else -- and save money and effort in the process”

Etherealmind and myself have been singing this song for quite some time (probably upsetting a few people working for my favorite vendor), but this time it comes straight from EMC’s CTO. And he didn’t even mention FCoE in his list of storage protocols.

Someone mentioned a while ago in a comment to one of my blog posts that the Nexus 4000 switch already supports multihop FCoE. Now that we know what multihop FCoE really is, let’s see how Nexus 4000 fits into the picture.

The Cisco Nexus 4000 Series Design Guide starts with a confusing set of claims:

• The Cisco Nexus 4000 Series Switches provide the Fibre Channel Forwarder (FCF) function.
• Nexus 4000 is a FCoE Initialization Protocol (FIP) snooping bridge.

A few weeks ago I wrote about the multihop FCoE basics and the two fundamentally different ways an FCoE network could be designed: FCoE on every switch or FCoE on the edges with DCB-extended bridging in the middle.

There are two other configurations you’ll likely see in access parts of an FCoE network: FCoE VN_port proxying and FIP snooping.

I’m writing this post while travelling to the Net Field Day 2010, the successor to the awesome Tech Field Day 2010 during which the FCoTR technology was launched. It’s thus only fair to extend that fantastic merger of two technologies we all love, look at the bigger picture and compare storage networking with SNA.