What is the single biggest threat to Cisco's networking empire? Before you answer, take a look at a business deal Dell just inked with a small voice-over-IP (VoIP) company. It could provide important clues about the future of unified communications in the small and midsize business market.

First, let's rewind to May 2007. At the time, I stated that there were five key threats to Cisco's networking empire. In short, the threats included:

1. No real CEO succession plan.
2. Recruiting and retaining talent.
3. Microsoft and Google.
4. Open source hardware.
5. Asterisk.

I goofed by not including "the economy" in my list, but I stand by the rest of my list ... particularly items 4 and 5. Indeed, open source continues to push deeper into the networking market. The latest example: Dell is about to announce a partnership with Fonality, an upstart that develops small business VoIP systems based on the Asterisk open source platform.

I traded email with a Dell spokeswoman earlier today (1/23/2008), and she indicated an announcement about the relationship is coming shortly via the company's Web site. Under terms of the partnership, Dell will promote Fonality's VoIP systems to businesses with 5 to 150 employees. (Dell will work with Nortel Networks on slightly larger engagements.)

What's the upshot for Cisco? Certainly, there's no reason to press the panic button. Cisco remains a networking industry powerhouse. Dell has stumbled over and over in the networking market. And Asterisk is a tiny threat at the moment.

Still, Cisco vs. Asterisk today reminds me of Microsoft vs. Linux a decade ago.

At the time, Bill Gates spent a lot of time (and money) dismissing Linux as a non-threat to Windows NT Server. Gates didn't expect IBM bet $1 billion on Linux, or former Sun CEO Scott McNealy to dress up in a penguin suit, or companies like Oracle to port all of their applications to Linux, or companies like Dell to pre-install Ubuntu Linux on selected PCs. (I have one; it's great.)

Now that Linux has gained critical mass (at least on the server), Microsoft is busy telling the world how well Windows and Linux (particularly Novell's SuSE Linux) integrate in data centers.

Five years from now, I suspect Cisco will be making similar interoperability statements about Asterisk -- particularly in the small and midsize business (SMB) market. SMBs are racing to embrace managed services and software as a service (SaaS). Dell, Fonality, Digium and plenty of other Asterisk proponents are eager to answer that call for help.

While no technology is immune to an economic slowdown (or a recession), I continue to believe that managed services, SaaS and open source will hold up better than traditional technologies in the months ahead.

Ultimately, Cisco will need a hybrid business model that marries the best of closed-source networking with open source solutions. During recent meetings, several of Cisco's channel executives described how they were watching the open source landscape. It was good to hear. But let's hope Cisco is paying more than lip service to the open source movement.