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Ethernet versus FC – Great ‘Surfer vs Banker’ Analogy #Cisco #NetApp #DCB

May 11, 2011

Read Part 1: http://www.networkworld.com/community/blog/ethernet-adapts-data-center-applications-%E2%80%93-pa

Read Part 2: http://www.networkworld.com/community/blog/ethernet-adapts-data-center-applications-%E2%80%93-p-0

Many networks need to marry their Fibre Channel SAN protocols to Ethernet. But Ethernet is an easy-going protocol (let’s call it West Coast) and Fibre Channel is a structured protocol (East Coast). “Data Center Bridging” will be to these two what the central country is to the Coasts – the means by which the two connect….

If we compare and contrast Ethernet and Fibre Channel (East Coast/West Coast derived protocols), we see that Ethernet is the laid back West Coast surfer that will try to deliver your frames on time and in order, but if they don’t you get a “Sorry dude, couldn’t make it happen” response but you’ll be OK because TCP will retransmit or for UDP, it was probably real-time traffic and hopefully didn’t notice the clipping.

Fibre Channel on the other hand is a very structured and regimented East Coast protocol that won’t tolerate delays and drops. Significant efforts are made to ensure this on-time delivery including a hop-by-hop buffering system and classes of service that can guarantee in-order delivery. If Fibre Channel frames hit the deck, bad things happen. Most applications and operating systems don’t like it when their storage is pulled out from under them while the network converges – recent personal experience was a great reinforcement of this principal. Wonder why your SAN admins get nervous when you mention FCoE? The laze-faire approach of Ethernet is the reason.

So how do we solve this challenge and merge the East Coast rigidity of Fibre Channel onto the West Coast laid back Ethernet – Data Center Bridging is the answer. Data Center Bridging (DCB) is a collection of enhancements to Ethernet that make it capable of providing lossless transport for protocols like FCoE….

Ethernet inherently doesn’t provide the ability to multi-path because STP is blocking our redundant links to mitigate loops in the network. So if you are implementing Fibre Channel over Ethernet and have promised your SAN team that the network won’t lose their Fibre Channel frames, the next hurdle will be multi-pathing. (See previous post that discussed the ways Fibre Channel and Ethernet don’t get along, and why Data Center Bridging is the answer.)

How do we cross that chasm? There are two approaches that relate to how you plan to implement FCoE in your network… single-hop, and…multi-hop.

Read more of the full articles at above Link

Credit: http://blog.ioshints.info/2010/10/ethernet-versus-fc-surfer-versus-banker.html

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