Computer programs are functional, but they are also “literary works” that may be protected under copyright law. In December 2016, Arista Networks defended itself against a $335 million copyright infringement lawsuit from Cisco Systems. Cisco is now appealing the decision.Cisco Systems, the largest networking company in the world, is trying to prevent Arista Networks from building ethernet switches which partially rely on technology copied from Cisco. Now on appeal before Federal Court in California (9th Circuit), the legal question is whether aspects of the particular technology deserves copyright protection in the first place. [caption id="" align="alignnone" width="960"] ethernet switches connect devices together on a network[/caption] Copyright protects creative expressions of an idea, but not the idea itself. This "idea–expression dichotomy" therefore limits the scope of copyright protection. In an earlier blog post, The Copyright Between Oceans, I explained how the scène à faire doctrine was used as a successful defence in a copyright lawsuit regarding the novel The Light Between Oceans, and its subsequent film adaptation. When scène à faire (French for "essential scene") is applied, common or typical plot developments are denied copyright protection. This means that broad themes, storylines and ideas which are common in a particular genre remain free for use by authors, screen writers, and other artists. In the United States, computer programs are considered "literary works" under the Copyright Act, 17 U.S.C. § 101. Accordingly, scène à faire may be applied to preclude copyright protection from aspects of a computer program which are common or otherwise "dictated by practical realities." Practical realities include hardware compatibility, manufacturer design, and industry practice. Arista's defence turns on this concept.