A different kind of SDN? Programatic NMS with Management Layer Abstractions

I was at an internal event this week where we were going over some of the amazing things that HP is working on, some which will come to market soon, and some which may never make it out of the labs. 

To answer the obvious question: No, I’m not going to talk about that.  


But during one of the sessions, an interesting conversation took place which I wanted to put some additional thoughts down on paper, or e-paper as it were. 

As is the case so much in the industry right now, the conversation came down to a discussion around this question

What is SDN?

The speakers statement, which I’ll look at below, was that programatic NMS is NOT SDN.  Now he is a very smart guy and I do have to say that his presentation was very good, but I had to object to that particular point.  I’m still not sure if I’m right or wrong, but I think it’s worth at least examining the point. 

So first I’ll refer to Martin Casado’s slideshare presentation which you should check out as I’m going to take parts of it out of it’s context in an attempt to make my point.  ( As they say, when you take the text out of the context, all you’re left with is a con ).

For those of you who didn’t check it out, the presentation focuses on the idea that the true benefit of SDN is the power of abstractions. The idea that abstractions allow for much greater flexibility and evolution because you don’t have to worry about the fundamental underlying complexity.

Imagine if all the software in the world had to be written in assembler. I’ll wait while your body works out the sudden urge to scream and jump out a window.

Screen Shot 2012 08 23 at 3 08 07 PM


So one of the fundamental tenants of SDN is that

Abstractions are the way forward.

I agree with this 100%. Abstractions take away the underlying complexity and allows us to concentrate on the task at hand. 

So the slideshare preso above deals primarily with the idea of control plane abstraction in the sense that OpenFlow’s purpose is to allow for instructions sets abstractions to be sent to OpenFlow enabled switches which will allow them to bypass all the current control plane complexities that we all know and love in the current network paradigm.


I’m 100% in agreement with that.

But what is of particular interest to me is the idea of management plane abstractions. Now for those who don’t know already, I’m an HPN Solutions Architect and an avid evangelist of HPN’s NMS platform, HP IMC.  ( Full Disclosure ).  So I will be attempting to make this argument in context of what IMC is providing now and where I see it going. 



If one of the core ideas behind SDN is the idea that abstractions NEED to be created in the networking world to allow us to evolve past the current “protocol-per-problem” paradigm that we are all living in,

It seems to me that allowing management plane abstractions should also have value and should qualify as a type of software defined networking. 

I fully admit that this will not be as revolutionary as the idea of a complete control-plane abstraction like what OpenFlow is promising in the next 2-10 years. ( I’m not holding my breath ). But I do strongly believe that there is some pretty amazing benefits that can be gained today IF the management abstractions are in place.

As well, I also believe that this could easily be the current missing-link that will allow us to bridge the gap between where we are and where we want to be.



So let’s look at the following simple example so I can try and make my case.

Imagine, if you will, you are running a dual-vendor strategy. I know you all are, Gartner said it’s a good thing, right?  But now you have discovered that MOST of the current networking hardware manufacturers are offering NMS platforms that limited to managing their own devices. 

So let’s imagine that you are running Cisco and HP equipment in your network and you want to deploy a new VLAN across your data centre. 

Assuming that your NMS’s are single-vendor NMSs ( like Cisco Prime LMS ). You’re stuck  You MIGHT be able to login in to your Cisco Prime LMS interface and deploy VLANs, or you might be able to rely on VTP or GVRP/MVRP to take care of this for you. 

Now if you were using HP IMC, we have already abstracted the management layer to allow you to just say ” DEPLOY VLAN 15″ and the programatic NMS actually takes care of the rest. 

Check out this video for a demo.

So how does this work? 


Let’s take the a step further and look at this in the context of SDN. Imagine the following scenario if you will.

A user plugs in to the switch. What happens

1) The dot1x supplicant kicks in and says ” Hey NAC ( sorry BYOD ) server; Is this guy allowed?”

2) RADIUS server says ” Yup, but he’s a sales user, so he needs to go in VLAN 15 

So far, this is pretty standard, right? RADIUS server responds back with the tunnel-group attribute or some other proprietary VSA and the switch puts the user in the right VLAN, right?




The NAC software has no knowledge of whether or not that particular VLAN is actually present on switch where the user is plugged in.


So imagine if there was a programatic interface, like the eAPI in HP’s IMC that would allow the conversation to go like this. 

1) User plugs in to a switch, dot1X process takes place, switch contacts NAC software through RADIUS protocol and the RADIUS server says ” This user should be in VLAN 15 “

2) The NAC software checks with the NMS to see whether or not the VLAN which we are trying to deploy is actually present on the switch in question. 

3) The Programatic NMS would then check the VLAN database to see if that specific VLAN is present on the switch in question. In this case, the the NMS will respond with a no.

4) So now the NAC program knows that the user authentication is going to fail because the underlying infrastructure does not have the necessary services in place ( the VLAN ) to be able to complete the transaction, so it then asks the programatic NMS to deploy the VLAN in question to that switch. 

 5) The programatic NMS would then connect to the switch, and add the VLAN. The NMS would check the bridge MIB, or whatever other MIB might be present to verify that the transaction was completed successfully.

6) After some arbitrary time value, the NAC program would then ask the NMS if the VLAN is present on the switch.

7) The NMS would then respond with a resounding ” Yes! It’s there!” 

 8) The NAC program would then complete the RADIUS request, place the user in the right VLAN and everything is great, right?


The best part of this, no human intervention, the program is able to request a service from the network, the network is able to respond that it’s not present and reconfigure itself to meet the needs of the application. 


So where’s the abstractions?

Look at the flow above. The NAC program asked ” Is this VLAN present” it didn’t say “When I run the command show VTP Database, after you parse through it, is VLAN 15 present?”  which of course would not work on a juniper or hp switch. 

The NAC program uses the self-describing RESTful API calls like device id15

And the NMS responds with an XML output which does not contain that VLAN ID.

Then the NAC program sends an HTTP post to the NMS and says


note: I don’t have the eAPI SDK in front of me, so I’m making up those calls, I’ll try and fix them later with the real syntax when I have a chance. 

And then the really cool part happens.

If it’s a Cisco IOS based Switch, it uses the Cisco IOS switch device adapters which define the specific commands or SNMP OIDS to set the VLAN on that particular platform.

If it’s an HP Comware switch, it uses the HP Comware switch device adapters which define the specific commands or SNMP OIDS to set the VLAN on that particular platform.

If it’s an HP Procurve switch, it uses the HP Procurve switch device adapters which define the specific commands or SNMP OIDS to set the VLAN on that particular platform.



No matter what kind of switch that user is connected to, HP’s Intelligent Management Center will hide all of the underlying complexity from the NAC program and respond to the same specific RESTFull API call. 


So instead of all the device specific syntax, it’s almost like a simple conversation.

NAC Program to HP IMC ” Is VLAN 15 present? “

HP IMC to NAC Program  ” Nope”

NAC Program to IMC ” Can you please add it for me?”

HP IMC to switch ” Add VLAN 15 to your configuration “

HP IMC to switch ” You done yet? “

NAC Program to HP IMC ” You done yet? “

HP IMC to NAC Program ” I’m done”


Now are their other failure modes which should probably be checked? Absolutely, off the top of my head, you would also have to check the dot1q trunks between the device and the L3 interface for that particular VLAN to ensure that you have end2end L2 connectivity and you’re not going to create an isolated orphan VLAN which dumps you user into no connectivity, but that’s just adding more logic to the program.


So back to the original question: Does a programatic NMS qualify as SDN or not?

Let me through out the following description. 

A paradigm where a application can request a specific service from the network and the network is able to dynamically reconfigure itself to respond to the applications specific requirements. 


That kinds sound like software defined networking to me.

What do you think? Is it the law-of-physic changing paradigm that much of the media would have you believe is coming? Nope. But does it have value? I’ll let you decide. 


One thought on “A different kind of SDN? Programatic NMS with Management Layer Abstractions

  1. Hi Chris.
    Good article. Nice vision 😉

    In fact, this sounds very familiar to me. In @intellimentsec we also believe that abstractions is the way to go. But abstraction only does not relief administrators from configuration pain. What if you must ensure that configuration needs to be compliant with regulations or internal policies? What if models are incorrect? (i.e. they represent a non-true reality of your requirements) You still need to use an auditing tool to check low-level machine-generated configurations. Quite innaceptable in a highly automated world.
    We are also trying to solve these problems at http://www.intellimentsec.com

    Sergio Pozo. Intelliment Security CEO

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