For all the complexity underlying software-defined networking (SDN) — the shift to a DevOps culture, the ending of siloed organizational habits — one recurring gripe is that all these "open" and "standards-based" networking products don't operate cleanly with one another.

It's an old complaint in networking, but it's still on users' minds, as you could hear during last week's meeting of the Open Networking User Group (ONUG).

The topic didn't come up in a vendor-bashing sense. Customers realize vendors have a business incentive to "differentiate" their products.

"I don't believe that they're behaving badly," said Major General Sarah Zabel of the Defense Information Systems Agency (DISA), during her keynote talk. "They're behaving in their own interests. I would like to see them behave in a broader IT community interest."

The issue came up specifically in a session about network overlays. ONUG's user members, which include banks and other large enterprises, aren't satisfied that standards provide enough glue to stick vendors' products together.

"In interoperability between vendors, we haven't seen any growth," said Carlos Matos of Fidelity, during the session.

One major and well-known factor is that standards provide a lot of wiggle room. Some can be chopped up into constituent parts that particular vendors pushed for. Naturally, each vendor emphasizes the pieces it likes.

Specifically, Matos pointed out that he can't connect two network overlay segments that were created by different vendors. The makeup of VXLAN — the IETF standard for Layer 2 tunnels that form network overlays — differs from vendor to vendor. Cisco has pushed for a version based on Ethernet virtual private networks, but it's not universal.

"Everybody was trying to do the right thing, trying to implement what the IETF wanted, and we still couldn't achieve an interoperable solution without some effort," said Mike Cohen, a Cisco senior director of product management who was part of Matos's speaking session.

ONUG hopes to make a difference in these kinds of situations. The Open Interoperable Control Plane (OICP) is one of four open source initiatives the organization launched last week, hoping to press vendors to fix issues such as interoperability.

Cisco's Cohen, who's active in ONUG, said the organization could help "by forcing our hand" (referring to vendors collectively, not just Cisco).

But what if the standards bodies aren't responsive? ONUG founder Nick Lippis is adamant that ONUG won't become a standards organization itself. But if ONUG's ideas don't get implemented, he said it's possible ONUG members could create a new, standards-driving organization — one that will no doubt start with the letter "O."

Photo: Intuit's campus, where ONUG Spring 2016 was held.