To say it's been a big year for software-defined networking (SDN) would be beyond an understatement. And yet, 2013 felt like a year of heavy-duty stage-setting, with major players such as the OpenDaylight Project, VMware's NSX, and Cisco's Insieme spin-in all taking their places for the main event in 2014.

Here's our look at some of the most-watched and most-talked-about stories of 2013.

1. OpenDaylight launches

OpenDaylight has become such a fixture that it's hard to remember SDxCentral broke the story about it in February. As Matt Palmer introduced us to the group, setting off a near-industrywide state of alert over OpenDaylight's motives (not to mention its ties to Cisco). The project launched in April, and while it still draws some skepticism, it's gotten some non-Cisco support as well, and Executive Director Neela Jacques pledges to keep to OpenDaylight's open-source principles.

OpenDaylight is off to a slow start, and it's under the gun to get the Hydrogen code release ready by Feb. 4 — opening day for the OpenDaylight Summit in Santa Clara, Calif.

2. Cisco reveals Insieme and a wider SDN strategy

Nov. 6 was the day that Cisco unveiled Insieme at long last, spilling a wealth of information about its SDN plans — and yet leaving lots of gaps unfilled. The Nexus 9000 series of switches that are at the heart of Cisco's Application-Centric Infrastructure (ACI) aren't fully ready yet, and they do represent a forklift upgrade for data centers based on previous Nexuses (Nexi?).

As an example of the information gaps Cisco has yet to fill: ACI is driven by a central policy element, the Application Policy Infrastructure Controller (APIC). We don't yet know the details of APIC or what's in it. There's a lot to swallow here, and that might be Cisco's biggest problem — as analyst Mike Genovese of MKM Partners wrote in a Dec. 30 note, the enormous, proprietary nature of ACI might scare off AT&T, a big customer that's eager for off-the-shelf hardware.

We'll be hearing a lot more about ACI in 2014, especially as the battle lines firm up against VMware's NSX and against OpenFlow and, yes, even OpenDaylight.

3. Juniper ends the Kevin Johnson era

Under CEO Kevin Johnson, Juniper embraced the coming era of software in networking (it wasn't yet called SDN) and started resembling Johnson's former home at Microsoft — in terms of the executives being recruited, especially. Arriving in 2008, Johnson also brought a successful history with enterprise customers, a market Juniper was eager to tap.

It hasn't all worked out. Johnson had five major, new product lines to nurture under his watch; among them, QFabric has been considered a disappointment and MobileNext has been folded. Johnson announced his resignation earlier this year; his replacement, Shaygan Keradpir, took over on Jan. 1.

4. ONOS emerges as an SDN controller contender

In December, Matt Palmer broke the story that On.Lab is aggressively pushing its ONOS controller, reportedly looking for financial commitments from big players such as Ericsson and AT&T by Dec. 31. (Yes, that was Tuesday; we don't happen to have an update yet on who's signed on.)

Combined with the open-sourcing of Juniper's Contrail, this opens a new chapter in the battle for "open" SDN options, as Roy Chua noted in his Controller Wars 2.0 posts.

5. VMware stakes out its SDN ground with NSX

Nicira famously gave up OpenFlow for a new model of overlays. The results were launched in March with the announcement of NSX, but the real NSX coming-out party was at VMworld in August.

Whether NSX sets up a major clash between VMware and Cisco (or VMware and OpenDaylight), or whether VMware can be satisfied with NSX being a thin, hypervisor-like layer between hardware and applications, remains to be seen. Either way, it ate up a lot of the SDN discussion in late summer.

6. Big Switch's big switches

Where to start? The big-ticket items were a new strategy abandoning network overlays in favor of being "the bare-metal SDN company" and a new CEO: Douglas Murray, who replaced Guido Appenzeller. Big Switch also lost a VP of engineering (Howie Xu), and other executives.

And then there was the whole OpenDaylight issue. Big Switch submitted its Floodlight controller to OpenDaylight, but OpenDaylight ended up choosing a hybrid controller, and Big Switch walked away.

7. CloudNFV takes a stab at this NFV thing

It's one thing for a group to be open-source and nonprofit, but CloudNFV is, in a sense, open-source and non-revenue. Tom Nolle, president of CIMI Corp., gathered six companies to create CloudNFV last summer almost as a personal project, a chance to make sure that NFV gets "done right," at least in his eyes. And he's got a point. The extensive CloudNFV demo that I got in October was geared toward showing how the resulting framework takes network management into account and is relatively easy to program via XML.

8. Ubuntu questions OpenDaylight

This wasn't a screed about big companies controlling OpenDaylight (something ODP claims to be structured to prevent). Kyle MacDonald of Canonical (corporate caretaker of Ubuntu) was concerned about OpenDaylight succumbing to large-group dynamics, where progress becomes slow and unfocused. You don't have to agree with him to understand his point — in fact, the delay of the Hydrogen release arguably suggests he's on to something.

OpenDaylight's followers seem unfazed by MacDonald's criticisms. Shortly after the article ran, Brent Salisbury, network architect at the University of Kentucky, posted this rebuttal.