A very important networking algorithm (the [spanning tree protocol](https://en.wikipedia.org/wiki/Spanning-tree_protocol)) can very well be considered graph theory. 

In the original work (Radia Perlman, *An algorithm for distributed computation of a spanningtree in an extended LAN*, SIGCOMM '85 Proceedings of the ninth symposium on Data communications) the algorithm is summarized as follows:

    **Algorhyme**

    I think that I shall never seea graph more lovely than a tree.
    A tree whose crucial propertyis loop-free connectivity.
    A tree that must be sure to spanso packets can reach every LAN.
    First, the root must be selected.
    By ID, it is elected.
    Least-cost paths from root are traced.
    In the tree, these paths are placed.
    A mesh is made by folks like me,
    then bridges find a spanning tree.