4 Applications
The shortest-paths tree problem comes up in practice and arises as a subproblem in many network optimization algorithms. The shortest path tree is widely used in IP multicast and in some of the application-level multicast routing algorithms.
4.1 Multicast
In the age of multimedia and high-speed networks, multicast is one of the mechanisms by which the power of the Internet can be further utilized in an efficient manner. When more than one receiver is interested in receiving a transmission from a single or a set of senders, multicast is the most efficient and viable mechanism.
Multicast routing refers to the construction of a tree rooted at the source and spanning all desti- nations. Generally, there are two types of such a tree, Steiner trees and shortest-paths trees. Steiner trees or group-shared trees tend to minimize the total cost of the resulting trees. Shortest-paths trees or source-based trees tend to minimize the cost of each path from source to any destination.
In the following, we briefly describe two well-known routing protocols: the Routing Information
Protocol (RIP) and Open Shortest Path First (OSPF).
RIP is a distance-vector protocol that allows routers to exchange information about destina- tions for computing routes throughout the network. Destinations may be networks or a special