Take the 2-minute tour ×
Server Fault is a question and answer site for professional system and network administrators. It's 100% free, no registration required.

I understand the concept of FCoE. I have looked at the Wikipedia page and looking at the layer 2 frame diagram, it looks like FCoE really should "just work" on any Ethernet switch, but is this really the case?

If so, what do switches like Cisco's Nexus 5k or 6120P offer that normal switches don't (in specific relation to FCoE)?

I am just using those two switches as examples. On the Nexus 5548UP page for example it says the following;

Unified ports that support traditional Ethernet, Fibre Channel (FC),and Fibre Channel over Ethernet (FCoE)

Well if FCoE runnins over regular Ethernet, that why does it support "Ethernet and Fibire Channel over Ethernet"?

This is why I am curious as to weather FCoE will run on any Ethernet switch and these switches just support "bonus" features, or if you do indeed require a specialist switch.

Thank you.

UPDATE

I have read on the Internet that FCoE will run on normal Ethernet devices but without DCB advanced features won't work, can anyone confirm if they have done this. Is it just "ill-advised" as opposed to flat out "won't work"?

share|improve this question
    
What was it about my almost immediate answer to your follow-up question that made you un-accept my initial answer? –  Chopper3 Sep 19 '12 at 12:15
    
@Chopper3 You said "FCoE doesn't run over regular Ethernet though, it requires Data Centre Ethernet/Bridging" but according to that wiki article, in the Frame Format section, it looks like it would run over standard Ethernet to me, is it is literally FC encapsulated in Ethernet frames: en.wikipedia.org/wiki/FCoE#Frame_Format –  jwbensley Sep 19 '12 at 12:24
    
You missed the "FCoE requires enhancements to the Ethernet standard to support a priority-based flow control mechanism" from the same article. I designed and built one of the largest FCoE environment currently in production and have three Cisco CCIEs working just on this bit of my platform. But if you want to read the same wiki article that states it's needs DCE/DCB without having built any of this stuff yourself then I give up, you must know best. Good luck, oh and if you get around to simply googling this and see that EVERY other article you find states the same please ignore that too. –  Chopper3 Sep 19 '12 at 12:56
    
Oh so I did, well I'm rather sick at the minute so I'm not thinking too clearly (that's my excuse!). None-the-less, that isn't very definitive; "FCoE requires enhancements to the Ethernet standard to support a priority-based flow control mechanism", Sounds to me like FCoE switches are required for the support of priority based flow control, but not FCoE in general. It also says in that article "FCoE encapsulation can be done in software with a conventional Ethernet network interface card, however FCoE CNAs offload (from the CPU)" - So it can run on top of regular Ethernet then (like 802.3ab)? –  jwbensley Sep 19 '12 at 13:08
    
NO - NO IT CAN'T, I don't know how many times you need to hear this, whether a CNA can offload the encapsulation or it's done in software is irrelevant, FCoE packets cannot be accepted by the receiving device without a lossless L2/3 connection. Just buy the book I recommended, it's cheap and tells you everything you need to know. I just got diagnosed with cancer on Monday and to be honest it feels like you're trolling me to get me angry. Very few people are doing FCoE in production right now, I am, and I'm not in the business of bullshitting people and I'm not trying to sell you switches. –  Chopper3 Sep 19 '12 at 13:16

1 Answer 1

up vote 11 down vote accepted

FCoE doesn't run over regular Ethernet though, it requires Data Centre Ethernet/Bridging - an evolution of Ethernet that is only current supported on a very limited number of, typically high-end, switches such as Cisco's Nexus range.

THIS is a great, and surprisingly short, book that would pretty much tell you everything you'd need to know about the subject - I'd recommend it.

Regarding your UPDATE question, it's not an 'ill-advised', it's a 'packets won't form so will not work' thing. The specific error you'd see would vary depending on your CNA and its drivers but essentially there's no successful L2/3 connection so that's the kind of errors you get.

share|improve this answer
    
Thanks Chopper3, that is simple and clear, and I will check out the book. Ta! :) –  jwbensley Sep 6 '12 at 14:40
3  
Y U NO ACCEPT?! –  HaydnWVN Sep 19 '12 at 12:17

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.