1) Does OpenStack require an SDN to be successful?
Historically, no. There were two networking modes. In the future, expect that some level of SDN will be required via the Neutron part of the project.
More broadly, SDN appears to be a critical component to broader OpenStack success. Getting it right creates a lock-in for OpenStack.
2) If you have an SDN for OpenStack, does it need to integrate with your whole datacenter or can it be an island around OpenStack?
On the surface, you can create an Island and get away with it. More broadly, I think that SDN is most interesting if it provides network isolation throughout your data center or your hosting provider’s data center. You may not run everything on top of OpenStack but you will be connecting everything together with networking.
SDN has the potential to be the common glue.
3) Of the SDN approaches, which ones seem to be working? Why?
Overall, the overlay networking approaches seem to be leading. Anything that requires central control and administration will have to demonstrate it can scale. Anything that actually requires re-configuring the underlay networking quickly is also going to have to make a lot of progress.
Networking is already distributed. Anything that breaks that design pattern has an uphill battle.
4) Are SDN and NFV co-dependent? Are they driving each other?
Yes. The idea of spreading networking functions throughout your data center to manage east-west or individual tenant requirements (my definition of NFV) requires a way to have isolated traffic (one of the uses for SDN).
5) Is SDN relevant outside of OpenStack? If so, in what?
Yes. SDN on containers will become increasingly important. Also, SDN termination to multi-user systems (like a big database) also make sense.
6) IPv6? A threat or assistance to SDN?
IPv6 is coming, really. I think that IPv6 has isolation and encryption capabilities that compete with SDN as an overlay. Widespread IPv6 adoption could make SDN less relevant. It also does a better job for multi-cloud networking since it’s neutral and you don’t have to worry about which SDN tech your host is using.