When a company builds a web site in the real world, they assemble servers, routers, switches, load balancers and firewalls, wire them up, configure them and go live. But when that application moves into a cloud environment, things change. In a cloud model, the customer isn’t dealing with physical equipment. So who handles all the wiring? And more importantly, how do networking vendors get paid?

Many operational clouds still require their customers to corral their own machines, however virtual. Amazon Web Services is a good example of this. To build an application, the operator still needs to do what they do in the real world — assemble servers, routers and switches to make a data center — only this time, they’re configuring virtual servers instead of real ones.

On the other hand, development clouds like Salesforce.com or Google’s App Engine hide the underlying machines, and handle all the networking equipment — virtual and real — on behalf of their customers.

Either model means a big transition for the makers of traditional networking equipment.

Option 1: Virtual appliances

In a cloud world, the routers, firewalls, and load balancers run inside “virtual appliances” — virtual machines pre-configured to route, block or distribute traffic. Cloud users still have to configure and provision them.

Open-source software dominates the virtual appliance world. For load balancing, Pound is one open-source alternative. For firewalling, there’s IPChains; for routing, Xorp. Some clouds already include these components: Cloud builder 3Tera, for example, offers users a catalog of data center components, including many open-source elements, in its default configurations.

Some vendors stand to gain from a move towards virtual appliances. If you want the kind of service and support you’d get from a vendor, Vyatta does for networking what Red Hat did for servers and MySQL did for databases. And while Checkpoint makes equipment, its software-based firewalls are more easily deployed in a virtual environment than many of its appliance-only competitors. The pendulum swings back to software.

If equipment vendors want to target this market, they need to convert their equipment and licensing models to virtual appliances and differentiate themselves based on software functionality rather than on box color or port density. Companies like rPath and jumpbox both specialize in turning traditional software into virtual appliances.

Option 2: Sell to the cloud operator

But what if the cloud handles the network equipment? This is the case if you’re using a development cloud like Salesforce.com or Google’s App Engine, or if you rely on a turnkey cloud like Joyent or Heroku. The networking equipment vendor sells to the cloud operator.

Which is No Fun At All.

Selling to a utility is notoriously challenging. Carrier sales cycles take months or even years, during which margins get squeezed razor-thin. At the same time, the list of requirements grows dramatically. Because clouds buy tremendous amounts of equipment, they have strong negotiating power. And they often build their own management tools, removing the differentiation a vendor’s software provides.

To make matters worse, clouds may need different equipment. Vendors are innovating, of course: Cisco’s new high-end switching platform, the Nexus 7000, seems well suited to this task. Further, the company has had strong carrier sales since its acquisition of Stratacom in 1996.

Some clouds may even find they have the expertise and economies of scale to build their own equipment. By buying directly from chipset manufacturers and using open-source libraries, they can bypass equipment manufacturers entirely.

One way or another, it won’t happen overnight. While the advent of utility computing is sure to change the networking industry, it will be some time before the trend puts a dent in enterprise IT equipment revenues. Less than 2 percent of CIOs surveyed by Goldman Sachs considered cloud computing a priority.

But someday soon, that load balancer you deploy may be a virtual one. That means two big changes for equipment vendors. One, selling licenses instead of boxes; and two, repositioning their sales forces to sell to telcos and utilities.