marionnet.org — a virtual network laboratory

The team

The authors

Jean-Vincent Loddo

Background. After a laurea in scienze dell’informazione at the University of Pisa, he defended a PhD in computer science in 2002, prepared at the ENS (LIENS laboratory) and then at Université Paris 7 (Denis Diderot, PPS laboratory), under the supervision of Roberto Di Cosmo, with whom he had co-developed DemoLinux, one of the first GNU/Linux live CDs, as early as 1998.

Today. An associate professor (maître de conférences) in computer science at Université Sorbonne Paris Nord (formerly Paris 13), he does his research at LIPN (the Paris Nord computer science laboratory), on the semantics of programming languages, and has taught networking and programming at the IUT de Villetaneuse since 2003.

On secondment to the Université numérique Île-de-France (UNIF), he now develops MarioNUM, an educational cloud of virtual computer labs. The project grew out of Marionnet: in 2020, during the lockdown, its prototype, Mariotel, ran Marionnet in a browser window, with nothing to install on the student’s computer. MarioNUM has since opened up to every kind of computing lab (programming, systems, databases, mathematics and statistics, office software…), but it keeps from Marionnet the prefix of its name and its spirit: making practical work easier. Marionnet remains its tool for networking labs.

In Marionnet. His first two years of networking labs, in physical lab rooms, showed him their limits: the equipment to bring together (switches, hubs, cables, routers), rooms available only during the sessions, students who cannot carry on with the work at home, exercises that are hard to prepare, to mark and to share between teachers. In 2005, he had the idea of Marionnet.

He designed its graphical interface, from the study of how it would be used to the drawing of its windows, and laid down its overall software architecture. He also chose its languages, on which Marionnet still rests today:

Luca Saiu

Background. A computer science graduate of the University of Pisa, Luca Saiu joined the project in 2007 as a developer on a six-month contract, funded by the university through Jean-Vincent Loddo. When the contract ended, he became a PhD student at Université Paris 13, supervised by Jean-Vincent Loddo and Christophe Fouqueré, later president of the university, and defended his thesis there in 2012, on GNU epsilon.

Today. A computer scientist specialising in programming languages, he maintains two GNU projects: GNU epsilon, an extensible functional language built on a minimal kernel, and GNU Jitter, which generates, from a specification, language virtual machines nearly as fast as native code.

In Marionnet. He built two technically very demanding parts:

What they did together

Together, they designed the simulation architecture, that is, starting and controlling all the processes, and groups of processes, that bring the virtual machines (User Mode Linux), the switches and the cables to life, and that let the network be reconfigured while it runs. They led the project together for several years, and described how it was built in a 2007 paper, How to Implement a Virtual Network Laboratory in Six Months and Be Happy: the six months of the title are those of Luca Saiu’s contract. His contribution was such that Jean-Vincent Loddo wanted him to be co-author of the software.

Luca Saiu later had to leave the project, which Jean-Vincent Loddo has maintained ever since; the 2026 overhaul is his work. Both remain the authors of Marionnet, and both are advocates of free software: that is why Marionnet is free software, under the GNU GPL.

Who did what, 2005 to 2014

Silviu Bârsanu, a Romanian painter and sculptor who also taught art, drew the student puppeteers and took part in the project’s logo. He died in 2021; his drawing opens the project’s presentation page.

Volunteers later started about ten translations of the interface; their names are in the translation files. These translations were completed in 2026 with the help of AI, which also wrote the missing ones: the interface is now available in thirteen languages, the original English and twelve translations.

Thanks

Marionnet owes a great deal to other free software, whose high-quality building blocks it reuses. We thank Jeff Dike for User Mode Linux, Renzo Davoli for VDE, the Graphviz team, the authors of OCaml and the whole community that keeps GNU and Linux alive. Marionnet is our contribution in return.

Davide Vaghetti taught us how to configure virtual routers with Quagga. Thierry Hamon helped debug an early prototype and gave us useful suggestions. Joseph Cerrato, Christophe Fouqueré and Christian Lafont encouraged us when we needed it, and solved several administrative problems.

Université Paris 13 (now Sorbonne Paris Nord) funded Marionnet as an e-learning project while we worked on it; the IUT de Villetaneuse and the Institut Galilée supported us, and the LIPN provided us with hardware, an Internet connection and a very pleasant place to work.

Since 2026, the Université numérique Île-de-France (UNIF) has hosted this website and Marionnet’s downloads. UNIF