Spanning Tree

 I think that I shall never see
 A graph more lovely than a tree.
 A tree whose crucial property
 Is loop-free connectivity.
 A tree that must be sure to span
 So 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.