How open is "open?"

That's become a familiar question as practically every major vendor, in succession, has declared its version of software-defined networking (SDN) to be open. That's led to "opener than thou" debates. Specifically, a lot of companies criticize Cisco for having such a Cisco-centric version of open, where the gear is Cisco's, but the APIs to talk to it are open.

AT&T's team takes a pragmatic approach: They don't care, as Margaret Chiosi, an AT&T distinguished network architect, explained during her Ethernet & SDN Expo keynote in New York Wednesday.

"When we want 'open,' we really want common, Chiosi said.

As an example of what she means, consider where AT&T doesn't have that commonality: in connecting the SDN controller to the devices in the network. AT&T would like to have one API, common to all vendors, for that job. Instead, the carrier uses a translator layer, as Chiosi put it, which converts an API to vendor-specific commands. "We're hoping to only temporarily have this layer," she added.

This matters to AT&T because the company wants to heavily shift to SDN and network functions virtualization (NFV). AT&T reinforced that desire last week by revamping its Supplier Domain process, in which AT&T used to pick two suppliers for each "domain" of the network. Those two inevitably would be familiar, big companies, but AT&T appears to want to widen the field when it comes to SDN and NFV technologies.

It all adds up to "this modern architecture to help simplify and scale AT&T," Chiosi said — but progress is weighed down by the lack of open, universal interfaces and technologies.

Open-source development could help AT&T's cause, Chiosi thinks — and that goes for vendor-led open-source work (such as Juniper open-sourcing its SDN technology, to cite one arbitrary example) as well as the purely community-driven kind of open-source. "I would say that we probably want both. We would probably like to be more community than vendor-specific, but both are probably important," Chiosi said.

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