I follow the @vmware twitter feed and saw an interesting post on VMware offering Software Defined Networks via VXLAN. Now, I want to give a recap of what I consider the nirvana of SDN to be. Traditional LAN/WAN networking are built on the concept of the 7 ISO layers. When building a complex network infrastructure be it data center or WAN you basically have to recreate the wheel each and every time. You have to identify a physical design, a routing protocol, network addressing, WAN design etc. For complex data centers and networks this requires individuals with exceptional skill to both design and maintain. At the same time it’s not very modular at the higher levels. I’ll let an expert explain this better than I can here.
The idea of full SDN is to do to networking what OS developers have done to programming over the years. OS developers have redefined application development by creating abstracted layers for very complex subsystems. When was the last time you’ve seen a third party memory manager? SDN’s should do the same for networking. A data center or cloud operator eventually shouldn’t care about the hardware and device OS used to interface with a network infrastructure that provides 10GB connectivity to location X. They just need to worry about the interface to the network “application”.
We are a long way from true SDN’s. First all the plumbing work needs to be complete. This starts with projects like Openflow and VXLAN. VXLAN is an interesting concept. It basically takes Layer 2 traffic and encapsulates it into layer 3 packets. What’s the advantage? From a practical, since if you have a fast enough layer 3 data center network you can now extend your layer 2 virtual network across physical boundaries. In theory if you had a 1GB TLS connection between two sites you could have a distributed switch across the two data centers. From a virtual machine perspective you can have two virtual machines reside on the same layer 2 virtual network but be on two different layer 3 networks. Hopefully the below picture helps visualize the scenario.
This helps with technologies and applications that don’t work well at layer 3. VMware gives the example of HA. You could build an HA solution and not worry about re-addressing your VM’s if they failover to another data center. What if we took this further into the cloud? You could extend your layer 2 network into a cloud providers network without giving thought to their addressing scheme. Since the layer 2 data is encapsulated none of your cloud vendor’s layer 3 devices are involved in the lower level intelligence.
Now add virtual routers or vShield to the equation. You can nest an entire virtual network independent of the physical stack. Now this is sounding more and more like SDN. May be now that I’m done with my Master’s program I can play around with these types of technologies in my lab.
What challenges could VXLAN help your organization over come? What short comings can you think of for VXLAN or SDN?