The aim of this research pro ject is to explore university students' learning of advanced computer science concepts in an internationally distributed pro ject course with the overall objective of improving learning and teaching of computer networks. This paper summarizes a full report that was previously published as a licentiate thesis at Uppsala University, Sweden (Berglund, 2002) and has been discussed at a licentiate seminar in March 2002. In this paper, I will start by describing the pro ject the students are taking. In the following section, I will discuss phenomenography and motivate my choice of this research approach. Section 4 brie y presents students' understanding of the network protocol TCP, while the last section discusses implications of the results for learning and teaching.