What's your view on how these people actually impacted the adoption of SDN in general?
> The investments NSF made in SDN over the past two decades have paid huge dividends.
In my view this seems a little overblown. The general idea of separation of control and data plane is just that - an idea. In practice, none of the early firms (like Nicira) have had any significant impact on what's happening in industry. Happy to be corrected if that's not accurate!
Depends where you are in the industry - the hyperscalers specifically have budget to afford a team to write P4 or other SDN code to manage their networks in production, so they're probably the biggest beneficiaries.
Lower end, it did make programmability more accessible to more folks and enabled whitebox switches to compete against entrenched players to a far greater extent than previously possible. Again, hyperscalers are going to be the main folks who buy this kind of gear and run SONiC or similar on it, so they can own the full switch software stack.
Many of the startup companies in the SDN space did have successful exits into larger players - for example Nicira into VMWare, Barefoot (Tofino switch chip) and Ananki (the ONF 4G/5G spinoff) into Intel. Also, much of the software was developed as open source, and is still out there to be used and built on.
What are some of the SDN open source software that is still useful today ? e.g. ODL, ONOS, Ryu, Floodlight
ONOS is being used with VOLTHA to enable PON networking in various locations (For example DT in Germany: https://convergedigest.com/deutsche-telekom-taps-open-source... , and IIRC it's also in production in Turkey).
There was a Comcast deployment to trial ONOS + whitebox switches a while ago.
The specific interplay of commercial deployment to open source vs commercial closed source in the networking space was better described in this post from Larry Peterson: https://systemsapproach.org/2022/02/28/venn-diagram-engineer...