SDN is about Programmable Networking

November 21st, 2012

The hype of Software Defined Networking (SDN) is alive and well. Many are advocating changing the classical IP model and moving to a network where a centralized controller makes all forwarding decisions by pushing forwarding states directly to switches. Is the Internet ready for re-invention? How should one react? What happens to the decades of IP protocol development and deployment that make Internet communications tried and true? Legacy vendors undoubtedly feel defensive, while new, innovative vendors are excited. At Arista we see an inflection point where we can bring together the best of both worlds.

Why do we need an SDN Controller?

The first question to ask is, “What is a controller and what problem is it solving that today’s networks do not?” The common answer: the configuration management automation problem. Historically, networking vendors have relied solely on a CLI or on SNMP agents for this capability, and have not excelled in this regard due to the inefficient nature of CLI and SNMP interfaces. The industry consequently is hungry for a platform that provides proper traffic monitoring, configuration management and useful network visibility and that results in reduced operational costs. When coupled with the trends towards network virtualization, the massive scale of cloud networks and big data, the insatiable demand for better tools is unquestionable. However, one must beware that the overzealous controller advocate might try to recreate IP networking and may not understand the pitfalls inherent in retrofitting a network with an overlay in an attempt to achieve high availability, scale and interoperability. No CIO is going to manage their 30 global data centers with controllers using proprietary orchestration protocols with an entirely new centralized control plane model. But every CIO is looking to reduce their CapEx and OpEx costs through modern methods of networking. Efficient, centralized workflows and management need a programmable network.

Distributed Controllers = Programmable IP = Arista EOS

It is clear that the industry has a void when it comes to building reliable, cost-effective and high performance networks at scale, and thus has developed an insatiable appetite to enable SDN. In technical terms, this means we need mechanisms to program forwarding state real-time into thousands of devices in a cloud network using familiar IP. The coordination of network state via the proper orchestration protocols is an important step and requirement of SDN.

Controllers are software elements at their core. So why can’t one run controllers/control points in a highly distributed fashion across network switches? This allows coordinated orchestration protocols and provides reliable connections between the networks and switches. A distributed controller is the re-invention of a highly distributed IP network with Programmability.

It matters less if an SDN controller resides external or internal to a network switch. But, the network software must be highly available and programmable. Arista Extensible OS (EOS) excels here and delivers this programmable networking today. Written from a clean sheet of paper with 10,000+ man-years of development, it offers complete isolation of network state residing in the control plane from the data plane, making it the only modern Software Defined Network OS in the market capable of cloud networking scale. Arista EOS is not only controller-friendly but can be a distributed control point as well.

Many SDN Facets – Not one Silver Bullet

The bottom line is that by solving the operational problems of a centralized control plane we wind up realizing that we are not discovering a new paradigm or inventing new switch/router designs. We are, however, greatly enhancing the last three decades of control plane/IP engineering and ringing in the modern 21st century of Programmable Networking.

SDN encompasses many facets and means different things to different people, be it OpenFlow, OpenStack, VXLAN or operational control points. The key in each use case is to not reinvent IP but make it more programmable, open and operationally manageable while building upon the last three decades of expertise. Welcome to the new world of Software Defined Cloud Networking. As always I welcome your comments at

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