|  | 11.2 | Why Routing Protocols are Necessary
| 11.2.7 | Three classes of routing protocols
Most routing algorithms can be classified as one of two basic algorithms: distance vector; or link state. The distance-vector routing approach determines the direction (vector) and distance to any link in the internetwork. The link-state (also called shortest path first) approach re-creates the exact topology of the entire internetwork (or at least the portion in which the router is situated). The balanced hybrid approach combines aspects of the link-state and distance-vector algorithms. The next several pages cover procedures and problems for each of these routing algorithms and present techniques for minimizing the problems.