1. What is software-defined networking?
SDN is a strictly defined concept, separating out the job of switching packets (the “data plane”) from the decision-making on how to switch them (the “control plane”). SDN differs from traditional routing protocols, such as Border Gateway Protocol and Open Shortest Path First, which seek to discover the fastest, most efficient path through the network.
Instead, SDN takes into account all sorts of other factors that are difficult or impossible to express in normal network routing protocols. For example, you may want to route traffic over a particular path because it’s less expensive or more secure or has more capacity. That can be hard to express in traditional routing, but it’s easier with SDN.
2. Are SDN and network function virtualization the same thing?
No. SDN is all about redesigning data center networks. Network function virtualization is about moving “middleware” (such as firewalls, Network Address Translation and load balancers) into your virtualization environment without using traditional specialized hardware. Virtualizing these middleware functions can be simpler in a data center that has SDN, but they are really independent concepts.
3. Where does SDN fit in my campus network?
The most advanced SDN products are designed for data centers and have complex applications in them. When an application has not only three tiers, but also dozens of moving parts that must be tightly and securely connected, SDNs can create the optimized paths and security separations that are hard to build manually using traditional virtual LANs, dynamic routing and switching.
4. If my applications are in the cloud, should I be investigating SDN?
As a data center technology, SDN isn’t going to be that interesting if you’re shuttering or seriously downsizing your data center LAN. Your cloud service provider may be using SDN products, but that should be invisible to you.
5. Can I use SDN in my WAN?
The SDN products being introduced for secondary campus locations are a different kind of SDN — more like second-generation WAN optimization. SD-WAN can build more reliable, faster and cost-effective networks on top of different WAN technologies.
SD-WAN is much more application-aware, and it makes routing decisions based on applications, user load, congestion, link cost and more. It isn’t the type of SDN that you’d find in a data center, but has the same central idea of increasing the intelligence of the control plane.