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Network Virtualization vs. SDN

4/20/2013

6 Comments

 
Bruce Davie, former Cisco Distinguished Engineer and now Principal Engineer in the Networking & Security Division of VMware via Nicira, did a pretty good job at confusing the audience this week at the Open Networking Summit (ONS) during his presentation.  While most other presenters talked about Network Virtualization as an application of Software Defined Networking (SDN), Davie wanted to state repeatedly they are different and that network virtualization is possible without SDN.  This is true, and unlike most vendors, he was actually trying not to SDN-wash.  Shouldn’t that be a good thing?  

For anyone that’s been following the SDN space for a while knows that this falls in line with what Martin Casado, OpenFlow creator and Nicira co-founder, has stressed over the years -- Nicira’s goal is/was to virtualize the network, not evangelize or sell Software Defined Networking (SDN).

Here is the thing.  It is possible to deploy network virtualization without SDN and without a controller.  For example, in the current vCNS VMware networking architecture (pre-Nicira), it is possible to deploy VXLAN along with vShield Edge and App appliances.  You can also deploy Cisco Nexus 1000V with vPath, VXLAN, ASA 1000V, and VSG.  These designs offer properties of the physical network in the virtual network by abstracting the underlying network hardware deployed via overlay protocols (w/ mcast) and NFV (network functions on VMs) with centralized management and integration to Cloud Management Platforms.

With Nicira networking, a controller is used as the control plane in that it manages the proactive setup of certain flows by creating MAC to VTEP entries (using VXLAN as an example; STT could be using different terminology).  The solution also offers gateways to get from the overlay to the traditional/legacy world and then other nodes that are used for controlling BUM traffic.  Does what they are doing make the Nicira solution SDN or simply a control plane for an overlay encapsulation protocol that compliments local MAC learning? 

By the most concrete and succinct definition given at ONS, it may not be SDN.  This definition was that of Nick McKeown, Professor at Stanford, co-founder of Nicira, Board Member at the Open Networking Foundation (ONF), and PhD advisor to Martin Casado.  The definition went something like this:  SDN has two properties (1) physical separation of the control plane and data plane and (2) a single controller (control plane) can control multiple devices.

The control plane Nicira developed adds entries to the already existing MAC table in Open vSwitch.  So, OVS still performs local MAC learning.  It still has a control plane, no?  If this is incorrect, please let me know.  Nicira also handles BUM traffic with their complementary control plane.  The point – there is still a local control plane on each switch – Nicira did not want to re-invent basic functions of switches as can be inferred from reading several articles by Nicira and Casado at Network Heresy.

However, since their controller cluster is integrated to Cloud Platforms such as OpenStack, it could be possible to fully extract each switch’s control plane and manipulate the MAC/flow tables as new VMs are created, moved, etc.  Maybe we’ll see it evolve to this; because of their current architecture, it is already completely possible to accomplish though.  They would only need to write their own control plane to replace local MAC learning.

But, other vendors are leveraging controllers to manage overlays like Nicira and selling it as SDN while Nicira sells the Software Defined Data Center (SDDC).  The way each enables MAC to VTEP manipulation or any type of control plane could be different.  That would be a point to compare between different network virtualization solutions.

Personal perspective: While Nicira executives may like to really be specific on Network Virtualization vs. SDN, you know their sales teams are in fact selling SDN solutions today regardless of what is written or said at public conferences.

Based on McKeown ‘s definition, here are two closing questions.  (1) Can a switch that performs MAC learning be called SDN? (2) Can a MAC table exist on a switch and be called SDN?

At the end of the day, what really matters? If network virtualization fixes the problem and it’s not with OpenFlow or SDN, should that matter? 

As usual, if anything is not accurate as stated, please let me know.

Related links:

  • An Evolutionary Approach to SDN 

  • Is OpenFlow/SDN Good at Forwarding?

  • VXLAN, IP MULTICAST, OPENFLOW AND CONTROL PLANES

  • Network Virtualization Part 1

  • Network Virtualization Part 2

Thanks,
Jason


Twitter: @jedelman8

6 Comments
Cristiano Monteiro
4/20/2013 08:07:30 am

I think what nicira/vmware wants with such kind of presentation is to defend software abstraction to the physical network. It makes sense if you are a software company. However a complete abstraction doesnt seem the only way here. Eg terminate a overlay tunnel at ToR where n virtualization inside the rack, service appliance ... may require a hybrid approach.

Reply
Jason Edelman link
4/20/2013 08:41:33 am

Defending software abstraction or terminating an overlay in a phy TOR still doesn't change much in the NV vs. SDN or the NV as an application of SDN discussions though. From a TOR perspective, they'll end up partnering - they need high performance gateways to get out of the overlay.

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Cristiano Monteiro
4/20/2013 09:48:46 am

When you write NV x SDN. I read software only solution x hybrid solution. Look it doesnt apply to everything but applies very well in datacenter what I think it's the target in Bruce Davie presentation.

Cristiano.

Eli link
1/30/2014 06:06:38 pm

I like the way in which you have designed your blog. It is very easy to read and see. Will you please update more posts for helping your visitors?

Reply
Matt link
6/9/2014 02:08:47 am

As a network engineer who´s only getting into NV and SDN via the posts and news on Network Admin and World - it happens quite often that I get lost and cant really figure which concept forms a part of which of these protocols/technologies. I like your posts cause the phrazing seems network engineer friendly, if I may put it like that, and I get it rather easily... so, I guess I just wanned to thank u :)

Reply
Jason Edelman link
6/9/2014 03:06:49 am

Matt, thanks for the kind words and thanks for reading!
-Jason

Reply



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    Jason Edelman, Founder of Network to Code, focused on training and services for emerging network technologies. CCIE 15394.  VCDX-NV 167.


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