Citrix Systems Inc. (Nasdaq: CTXS) wants to initiate a different way of thinking about software-defined networking (SDN), one that involves developing a Layer 4 through 7 architecture that can work with any switches or routers, and it has recruited a handful of industry partners to its cause.

The big switch/router guys aren't among them -- not because Citrix doesn't like them, but because the idea is to have those upper layers send policy-driven commands to Layers 2 and 3, using the application programing interfaces (APIs) that vendors are hoping become standard elements of SDN.

SDN, by most definitions, involves using programmability to make the network easier to change and services easier to provision. Most of the publicity has gone to Layers 2 and 3 -- the switches and routers that would execute these changes -- but the whole point is to make life better for the applications, Citrix and others argue.

"We think the SDN stack was only half full" until now, says Sunil Potti, vice president of Citrix's Cloud Networking Group.

Citrix announced Tuesday that it's adding application smarts to its Netscaler SDX platform, which runs multiple, separate application delivery controllers (ADCs). Netscaler would be able to make policy decisions based on application requirements, then push those decisions down to routers, switches, OpenFlow controllers or whatever else is guiding the switch/router network.

Netscaler isn't ubiquitous in the network, though, so Citrix is trying to gather partners, particularly in the area of security, to go in on this vision; eight of them, including Aruba Networks Inc. (Nasdaq: ARUN) and RSA Security Inc. (Nasdaq: EMC), were announced Tuesday.

Citrix also announced a deeper partnership with Palo Alto Networks Inc. , where the two are developing ways to combine security and application delivery in a cloud environment, where users and applications can all be in varying places.

The companies have been talking for more than a year, Potti says. They've decided to join up at a deeper level because they share similar ideas about SDN and have been ending up side by side in a lot of networks.

"We are in common deals more often than not, and customers are happy we are not trying to forklift each other," Potti says.

— Craig Matsumoto, Managing Editor, Light Reading