SDN side by side comparison with the OSI Model

Hello all,

Digging into SDN more wondering if anyone can offer a side by side comparison of SDN comparted to the OSI Model...

Thanks in advance.

So far;
Layer 7

Management plane

Control plane
Layer 1-3 ---- Data plane

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Comments

tunerX

SDN pulls the control plane outside of the model. SDN can sticks its grubby little fingers in all layers if there is a reason for it. The OSI is normally a reference to a single device where one layer from one device talks to its respective layer on another device.

If you think about OSPF, it is a protocol that concerns itself with layer 3. But it runs as an application receiving input and providing output with the sole purpose of making intelligent routing/layer 3 decisions.

SDN just moves the control portion to a different area or areas of the network/domain.

With that in mind, if you think of OSPF again. It would be like having the linkstate database and all of the application control that revolves around building the OSPF topology contained to a specific controller. Instead of having OSPF running on every router making independent L3 decisions. You have OSPF running on an external device/controller making the L3 decisions for every device.

SDN isn't that cut or dry but my example shows how the control of a device does not have to exist on the device that is layered based on the OSI.

boxerboy1168

From this I can extrapolate that SDN separates the logical control mechanism from the actions of OSPF...

Ok.... so SDN gives me more granular live control over the OSPF routing protocol...?

Does SDN only apply to virtualization or is this network wide?

Not sure if I'm using the correct lexicon.

networker050184

What is it exactly you're trying to figure out? SDN and the OSI model are completely different things.

boxerboy1168

Just trying to understand more how SDN works. Thought you could put a side by side comparison of how the networks actually function from a top down perspective like in the OSI model but apparently it doesn't really have that kind of functionality.

tunerX

boxerboy1168 wrote: »

Just trying to understand more how SDN works. Thought you could put a side by side comparison of how the networks actually function from a top down perspective like in the OSI model but apparently it doesn't really have that kind of functionality.

SDN is a new paradigm in networks. Instead of having a bunch of stovepipe routing/networking devices all with their own configurations, control planes, and data planes (all following the OSI). You strip away some of the control plane smarts and make a cloud based control plane that can see the whole network all at once and can use any device or path to create fully optimized/utilized networks.

Ideally you will want an expert machine running the whole network. Looking at constant metrics and information that is being provided by each device. It will detect failures and adjust the network to match or it could be very smart and detect when problems are about to happen so it can adjust traffic before failure.

boxerboy1168

Awesome explanation thanks!

So SDN has better vision over the network and can streamline routing and switching?

Am I understanding that?

tunerX

That is the goal.

I haven't seen that many good implementations where the controllers are better than people, and current technologies, at making decisions.

boxerboy1168

So SDN isn't common?

Essentially still in beta?

tunerX

It's not really in beta and it isn't that common unless you are into data centers and service providers. The majority of networking is still SMB and enterprise.

When first made an entrance it was being touted that it was going to replace all of the networking on the planet in a couple years. fast forward to today and we find out that it is really, really, good in data centers and some ISP cores but not all networks are DC and ISP.

boxerboy1168

They don't/can't use it for asynchronous networks or to streamline BGP?

ccie14023

Not to fully dispute what has been said before... But the fact is you are looking for a technical explanation of a non-technical term. While SDN may originally have referred to separating control/data plane, it's taken on a life of its own and become a generic marketing term for nearly anything that uses software to manage networks. Even classic management systems are being rebranded "SDN controllers." As it is, the control/data plane separation is not all that new of an idea. (Think BGP route reflectors.) It's also an idea that has a lot of problems. I highly recommend Ivan Peplnjak's writings on the subject (ipspace.net) for some clarity on the hype, whether control plane separation is needed, etc., etc.

boxerboy1168

Thanks! Checking it out!