What is Open SDN? A Definition

Software-defined networking (SDN) and network functions virtualization (NFV) have a vast open source community, committed to growing projects that promote open standards. To better understand open source, it’s important to understand first what open SDN entails.

Source: Open Networking Foundation | SDN Architecture

Attributes of Openness in SDN

SDN allows for the programmability of the control plane and the abstraction of the application and networking services in the infrastructure by separating the network control and the forwarding functions in the architecture. SDN revolutionized networking by offering advantageous benefits, such as it achieves inoperability between physical and virtual devices and is vendor-neutral, it provides constant visibility of networking flows, it has a single management framework for all devices, it’s programmable, and it allows for automation.

In the aspiration to advance networking technologies, organizations formed that allow anyone to join and to freely use its code as long as each member contributes to the project. That’s the basic premise of an open source community. When trying to ascertain what is and isn’t open, remember that one or more of the below can help determine openness.

Open Standards: Freely and generally available specifications for hardware or software developed and maintained through a shared process, like OpenFlow
Open Source Software: Source code available for anyone to modify or enhance, like OpenStack and OpenDaylight
APIs and SDKs: Application program interfaces (APIs) act as tools for creating software applications, often dictating how software components should communicate with one another (not all APIs are open, consider Amazon Web Services APIs); software development kits (SDKs) are packages of pre-written code that minimize the amount of unique code developers have to write themselves; several SDKs are published APIs, available for anyone to write into their own applications
Open Hardware: Designs with open reference for compute and networking products, like Open Compute Project

The above gives a glimpse into why many companies and organizations can label the entity or its products as “open.” However, when contemplating what is and isn’t “open,” one must consider the degree or type of openness attributed to a certain product or company.

Foundational technologies — considered the building blocks of SDx (software-defined everything) — can be SDN/NFV products, including protocols, SDN Controllers, vSwitches, or or application programming interfaces (APIs). These technologies are held to a higher standard than supporting technologies, which enable other technologies to interact with each other.

How to Determine a Project’s Openness

Consider these areas when trying to understand the degree of a project’s openness.

Contribution and/or Participation Requirements: Participation requirements sometimes depend on the project. The Open Networking Foundation (ONF) requires membership, while OpenDaylight allows anyone to participate, but only paying members have voting rights. An easy rule of thumb when determining a project’s openness is to pinpoint the top 10 contributors. If more come from a single company, the less likely the project is more open.
Governance: This refers to the process a project follows when accepting code contributions. While every project has its own methods and processes, it’s important to identify who holds responsibility of standards.
Intellectual Property Protection and Licensing Rights: Free and open software (FOSS) gives users the ability to run programs for any purpose, as well as alter and redistribute them without paying royalties to the original developers. Reasonable and non-discriminatory (RAND) licensing assurance means the patent holder will not gouge the market with licensing fees once the standard is adopted. Both of these licenses reduce legal risks and point to a more open project.
Ownership and Ability to Fork: Intellectual property (IP) disputes are not few and far between, so knowing who ultimately owns the open standards or open software is important for openness. Make sure an agreement dictates who will own the TP that results from any open project. Also, be sure to ask if a final product can be “forked” — turned into a unique piece of software based on source code from someone else.

To be truly open, foundational technologies must meet the following criteria: FOSS-based licensing; a level of clearly defined IP protection to ward off patent infringement or copyright claims; an open and transparent governance model with a board that represents the entire community; and open participation requirements that offer well-established merit-based processes on how code will be accepted.

SDxCentral holds foundational technologies to a higher standard than supporting technologies, or those that enable other technologies to interact with each other. SDxCentral also believes the most truly open projects are those governed by an independent foundation.

When taking into account these factors, the projects OpenStack and OpenDaylight could be deemed more open due to their open allowance of contributors, the foundation governance, and their free and open licensing rules (Apache 2.0 for OpenStack, Eclipse Public License for OpenDaylight). Also based on SDxCentral’s criteria, the most open foundational technologies would be found in any software project or protocol from the Apache Foundation, Internet Engineering Task Force (IETF), Linux Foundation, or ONF.

SDN & SD-WAN Open Source

The application of SDN to network connections across a wide geographic area is called software-defined wide-area network (SD-WAN). SD-WAN is considered an addition of SDN in that it uses it to unify networks within an enterprise despite geographical distances. This technology has seen a rise in popularity among enterprises for several reasons, mainly for cost-effectiveness and for enhanced security. Another important reason there is a growth SD-WAN usage is due to its open source technologies. The SD-WAN open source resources provide customers with a way to access SD-WAN at a lower price point. The open source community also spurs advancement in the technology.