First published at: SDxCentral

Telecom operators (telcos) and Internet providers (ISPs) operating in challenging environments require use of dynamic topology adjustment (switchover from primary to backup communication channels) to ensure connection stability and continuity. This usually means opting for an expensive network management system that gets the job done, but has a number of downsides. However, there is a low-cost and low-effort way to enable network topology switchover using open source software-defined networking (SDN) solutions.

Enabling Switchover in an Unstable Network: What are the options?

Maintaining stable connection across several distributed locations – that’s a case scenario not uncommon among telecom providers. In addition, it’s typical for wireless communication channels to be exposed to bad weather conditions, which puts the connection stability under serious risk. This is where switchover comes into play, by automatically switching between communication channels in case one of them fails.

When it comes to enabling switchover, large providers may opt to acquire an expensive network management system that will ensure connection stability, but requires compatible hardware throughout the network. Ultimately, this results in vendor-lock and significant total cost of ownership increase. Another option would be to hire a team of system administrators to monitor the network day and night, and address the malfunctions in real time. None of these options seem like a cost-effective one.

There is actually one more “hidden” option – to utilize the power of open source SDN solutions to get a reliable production-grade system for dynamic adjustment of network topology.  It sounds too good to be true.

Let’s get back to what SDN actually does. The cornerstone of SDN is making the network’s control logic centralized and software-based. The basic recipe for an SDN network is OpenFlow-enabled equipment plus an SDN controller, topped off with an SDN application. We are going to talk about using open source SDN solutions on each of these levels in order to maintain a stable wireless Internet connection, even on an island in the storm.

Step 1: OpenFlow-Enabled Network

OpenFlow is essential to SDN, as it enables communication between network devices and the SDN controller. There are actually several ways to introduce OpenFlow to your network. One way is to replace the devices’ firmware with the OpenWrt operating system and install Open vSwitch (OVS) on top of it. The latest versions of OpenWrt already include OVS, making it even easier to implement an SDN network.

Step 2: Choosing an SDN Controller

The SDN controller is the brain of the network. It is responsible for building and displaying topology, programming network devices, and serves as a single management point for the entire network. Two of the most prominent SDN controller examples are OpenDaylight (ODL) and Open Network Operating System (ONOS), both of which can be potentially used to enable network topology switchover. The two controllers bear some similarities. They are designed for modular use with a customizable infrastructure and come with a number of default applications. However, ODL is more about bringing legacy networking and SDN together, while ONOS focuses on performance aspects and clustering to increase the availability and scalability, which makes it a controller of choice for Telcos and ISPs.

Step 3: Choosing an SDN Application

SDN applications directly interact with the SDN controller as well as providing a certain level of network abstraction and can serve as tools for network monitoring, control, and analytics. Since our goal is to enable switchover, we are interested in applications that provide accurate, real-time information about connection quality, and when it falls below an established threshold, addresses the SDN controller to re-route network traffic to a backup channel. There are actually open source applications that can effectively perform these tasks in cooperation with an ONOS controller.


SDN is one of the most disruptive technology domains today. A lot of businesses are still reluctant to adopt SDN because of its relative immaturity. However, using community-approved open source SDN solutions is a great way to get your hands on the advantages of software-defined networks without the need to make huge investments. In particular, telecom operators and Internet providers can greatly benefit from open source SDN solutions to ensure continuous connection without the need to purchase commercial systems, which are usually vendor-specific and expensive to maintain.