About 10 years ago, a few smart folks invented “Software Defined Networking” or SDN for short. SDN promised to “separate the data plane from the control plane”, but another objective was to break free from vendor lock-in. They wanted SDN to enable a network where one can design the network, manage it and monitor it without any dependency on a specific switch vendor. The concept was great, but the implementation started with OpenFlow, which for many reasons didn’t work so well and today is being used in a very limited way.
Compute and Storage have changed:
Let’s pause and see what happened with the other elements of the data center, compute and storage:
- The Compute side went “Software Defined” with the wide adoption of Linux and server virtualization. Long ago, data center operators broke free from vendor lock-in on their servers – no one would ever consider buying a server that only worked with just Windows or just one vendor’s flavor of Linux. And because they are free of vendor lock-in on servers, smart data center operators get better value and higher ROI from the resulting competition between server vendors.
- What about storage? While many consider storage to be slow in terms of adopting new technology, you might be surprised how quickly Software Defined Storage and Hyper-converged Infrastructure have taken hold. In fact, I dare you to go find a decent cloud running Fibre Channel… The number of true Software Defined Storage implementations is growing every day. Check out Nutanix with a very nice OEM strategy or Excelero who can replace your legacy SAN with your choice of servers…
What really happened to SDN
SDN is live and kicking, but what is SDN? – The answer depends on who you ask.
If you ask those who invested in OpenFlow, they will say SDN=OpenFlow, but there are not many of them left.
If you ask the incumbent switch vendors, they will give you a very comprehensive story about a single pane of glass, micro-segmentation, multi-cloud, etc. but how is that related to SDN? It’s hard to say, but maybe it’s the fact that they are selling you their proprietary controller, which sounds a lot like those SDN OpenFlow controllers? It’s hard to tell, but for sure the “incumbent SDN” doesn’t separate the control plane from the data plane, and doesn’t support a heterogeneous vendor switch deployment …
At this point I had to run a sanity check and checked Wikipedia, here’s the definition of SDN as of March 8, 2020:
Software-defined networking technology is an approach to network management that enables dynamic, programmatically efficient network configuration in order to improve network performance and monitoring making it more like cloud computing than traditional network management.
I must say that Wikipedia’s definition is very close to what I’d consider SDN today.
In order to achieve the goal SDN was created for, we need to focus on management. Not a single-vendor proprietary management offering, but a way to manage multiple vendors’ switches in a standard and simple manner.
What is SDN in 2020?
SDN is a modern network, that is managed through an automated API rather than manually through a CLI, enabling easy configuration orchestration and management, as well as a simple way to monitor the network.
What is a modern network?
- A simple network with as few protocols as possible
- A network which is based on L3 when possible, definitely between switches, preferably between switches and servers/storage
- A network which leverages VXLAN/EVPN overlays when it makes sense
- A network with great telemetry capabilities
- A network which is SOFTWARE DEFINED, meaning the switch network operating system software can run on different hardware, for example Cumulus or SONiC
- A network where the host defines policy, security and user profiles, the network is “just a network” – fast, efficient, easy to manage and most importantly – standard!
SDN was invented to break free from lock-in, allowing organizations to build the same management infrastructure once and use it with various networking vendors.
Many organizations are implementing real SDN networks today, that leverage Open Ethernet, standard Linux tools, ONIE based switches and enable choice of hardware. But today, the vendors shouting the term “Software Defined Network” the loudest, are actually those who build the most proprietary sole-source, vendor lock-in switch offerings.
So, don’t be fooled. Make sure when you choose a SDN, you can choose a switch vendor too!
Read more about Mellanox Spectrum Ethernet Switches: https://www.mellanox.com/products/ethernet-switches