At the risk of making this an all-SDN blog, I thought it would be instructive to try to understand OpenFlow by the light of what it isn't. That is: What kinds of practical networking policies can't OpenFlow currently express?
My understanding is that this list would include:
- RED, BLUE, or CoDel
- ensuring that contending endpoints or flows share the capacity of a congested link equally (e.g. with per-user queueing)
- serving as an endpoint for an IPIP or IPsec tunnel or VPN
- specifying that Skype's UDP datagrams should jump to the front of the line waiting to egress on a port
- limiting queue lengths to control "bufferbloat"
But I do wonder whether the phrase "software-defined networking" has turned out to be a bit broad compared with what the practitioners mean when they use that term.