Tag Archives: SDN

OpenFlow and software defined networks are here. Now what?

I just listened to a talk from Berkeley professor Scott Shenker yesterday on youtube http://www.youtube.com/watch?v=WVs7Pc99S7w that gave an excellent breakdown of SDN and he spoke of the need of the Network Operating System before SDN’s can become a reality.

When I think about it, I’m rather amazed that we haven’t created an abstraction for the network. His talk speaks about how relatively easily we’ve done this at layer 2 but how difficult it is to do at higher layers due to the non-modular design of the network stack. Applications shouldn’t be making calls to the network address but rather to the network service.

Interesting stuff. OpenFlow is a step in the right direction to creating the “BIOS” that we need. I’m especially happy that Google is at the bleeding edge of this in a production network.


Earlier this month I spent a few days at the Open Networking Summit in Santa Clara, Calif. and walked away certain I watched history being made in the networking industry. The emergence of the OpenFlow standard and software defined networking have been on my radar for a while, but at this event, the future coalesced.

The secret is out on SDN.

I’ve been following SDN and OpenFlow almost since its earliest days. I’ve been lucky enough to know Martin Casado since before Nicira knew what it was going to build and Guido Appenzeller of Big Switch of SDN since his days at Voltage Security. I attended the first Open Networking Summit back in October, but was floored by the scale of the April event. Attendance was up over 3x, and people from all corners of the ecosystem were there. Clearly the secret is out and it’s evident that the networking…

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Why No True Network Virtualization

So, I want to talk about network virtualization from another angle.  We know that with VMware you can create virtual switches and even outsource the process to the Cisco Nexus product line.  I think this should actually go farther out to include chassis virtualization. 

I worked for a pretty big hosting provider for a very short period of time and one of the issues we ran into was multi-tenancy.  For a smaller enterprise data center multi-tenancy isn’t too big of an issue that VRF and the like or even multiple chassis wouldn’t solve.  But for larger data centers this becomes an issue.  There are a couple of issues to address from physical space consideration to management and cable plant issues.

There are many instances where both internal and external customers would like the peace of mind that comes with virtualized hardware on the network side of the equation.  A good example would be a customized solution for a single customer or a set of customers in a shared cabling plant.

Today if you want to create this type of environment in the Cisco IOS world you’d do it via ACL’s, Route Reflectors and etc…  Why not just create a virtualized switch inside of the chassis?  A completely separate instance of the IOS to just simplify the whole configuration.  It would allow you to assign separate security settings for each instance.  I don’t know something like what Extreme has been doing for the past few years http://tinyurl.com/vojus.

I figured if Cisco can create a server with 512GB of RAM they could be able to virtualize their core offering – IOS.

I don’t think this is too farfetched of a request.  I like to play around with GNS3 located at www.gns3.net.  It’s a great little tool that is actually a hypervisor for Cisco IOS on Wintel platforms.  It’s not meant for production but technically there’s nothing stopping you from using it to do some really cool stuff in a lab.  You can map physical or virtual interfaces (think VMware workstation) to the logical Ethernet ports of the virtual routers.  You could in theory create a virtual DC of VMware servers on a single workstation running a virtual MPLS end node.  Connect that to another workstation running another virtual DC and MPLS node and have you a nice MPLS cloud running on one or both workstation.  If you have a beefy enough machine it could all run on one workstation.  If Cisco sends me one of those blade deals, I’d be more than happy to let you know how well it works.

My biggest complaint about the product is that you can’t virtualize Cisco switches.  You can do routers on a stick because you can still associate a physical NIC on your workstation to one connected to a Cisco Switch.  I’ve found it an invaluable tool for creating lab and test scenario’s.