With Insieme entrenched in stealth mode, Tom Edsall was limited in choosing a keynote topic for the Hot Interconnects conference on Thursday. Rather than giving away Insieme's entire plan -- which would have been nice but wasn't likely -- he sketched out his thoughts about the data center of the future, pointing out a few places where the software-defined networking (SDN) buzz and hype have so far fallen short.

Tops among that group are the debugging tools that would go along with this new, heavily virtualized data center. Applications will hop from host to host, theoretically, and that means there's no easy label, such as an IP address, that can pinpoint where traffic came from or even who sent it.

Network tools need to catch up with that concept, he said.

"Everybody hates spanning tree, but it told you where the data went. ... In a highly multipath environment, I don't know where to look for the data. I look everywhere" Edsall said.

A lack of tools for looking "everywhere" might constrain the choices of data-center topologies, as operators design networks for the sake of easy debugging, he said.

One example of a useful function would be a continual streaming analysis of what's happening in the data center network. What Edsall seemed to have in mind is a more dynamic version of Cisco's Switched Port Analyzer (SPAN) for Catalyst switches. What SPAN does is send a copy of data to another place for later analysis. It's "the dumbest feature out there" yet "one of the most important," Edsall said.

Also in the dumb-but-useful category are ping and traceroute, which remain the bread and butter of debugging. They'll have to evolve to suit a multipath environment, Edsall said.

Along similar lines, the concept of performance "needs to be thought about as application performance, not performance of the network," he said. "An application is dependent on the CPU and on the network and on the underlying storage. We have to think about all of these things together."

Networks are built to treat all applications the same way — "fairness" is of paramount concern — and applications are written assuming they'll run on a generic dumb pipe. A huge opportunity lies in bringing those sides together, Edsall said.

"Somebody is going to have to optimize [their application] for a network or a set of networks. The SDN controller guys are promising that, but I haven't seen it yet," he said. "It may mean not being fair in the network. It may mean dropping more [packets] than you want to drop. I don't know."

These ideas aren't radical; one audience member noted that everybody listening probably agreed with most of Edsall's points. But his talk was a good reminder of how much dirt-under-the-fingernails work lingers behind the promise of the software-defined data center — and in Edsall's view, a lot of that work hasn't even started in earnest.