An international court has handed Cisco an early victory in its lawsuit against hated rival Arista

On Tuesday, Cisco received a dollop of satisfaction in its ongoing lawsuit against hated upstart Arista Networks.

The International Trade Commission (ITC) issued its first ruling in two investigations into whether Arista's products are violating a handful of Cisco's patents.

A judge found that Arista infringed on three of the five patents at issue in this case and did not infringe on two.

Next, an ITC judge could ban Arista from importing some of its network products if Arista doesn't come up with ways to change the problematic product features, or come up with other workarounds.

Arista has been promising investors and customers for months that it's already prepared for a "worst-case" scenario and they shouldn't fear that the company will be hurt if Cisco wins the case.

Meanwhile, the two sides are spewing vitriol.

The lawsuit didn't cause the tensions. The tensions caused the lawsuit.

As we previously reported, Arista Networks is a company filled with former star Cisco engineers and employees working on a rival networking technology. It's like a family feud. And both sides are making valid points in some of their mud flinging.

Cisco has basically has accused Arista of "stealing" its technology, according to Arista co-founder and CTO Ken Duda (a former Cisco engineer).

Cisco's lawyer Mark Chandler wrote in his blog post about the ITC decision:

Based on our investigation, we believe that Arista's use of our IP was intentional, pervasive, and driven by the most senior levels of their organization to unfairly compete. Copying and misappropriation are not a legitimate strategy, and today's ruling is a vindication of our position.

Cisco is angered by the idea that Arista rather deliberately copied chunks of Cisco's "command line interface," (CLI). Those are the commands that customers use to operate network equipment. Arista doesn't deny using many of the same commands. By keeping them the same, Cisco customers had a shorter learning curve for Arista's equipment.

But Arista claims that these commands are in the public domain. It says that Cisco has trumped up the patent lawsuits because Arista is clobbering Cisco in the hot up-and-coming cloud computing data center network equipment market.

Duda writes (emphasis ours):

Struggling to apply old technology to the new world of cloud computing, Cisco is potentially facing the largest loss of data center market share in its history. We can understand why Cisco would take the battle from the marketplace to the courtroom. What surprises us is the length that Cisco has gone to misrepresent our actions and the nature of the litigation in order to justify their assault.

Most of the time, such lawsuits are settled out of court, and we wouldn't be surprised to hear that this one gets settled, too. Still, sources close to Cisco tell us that the company is hoping to force Arista to change its products and would be delighted if the ITC bans the products from entering the US from its overseas manufacturing plants.

In the meantime, Arista's tock is down about 2% after hours and down 26% since December.

An Arista spokesperson sent us this additional comment: "Our primary focus is the continued supply of products to our customers. We respect the administrative process and the tireless work of the ALJ in this initial determination."