Introduction to Multicast Route Construction

- Most commonly used to "price" the cost of a multicast tree:
- Each edge has a "cost" and the best multicast tree has the smallest total costs (of the edges in the tree)
- Each edge has a cost and the best multicast tree has the smallest
total cost from the source to
**any**muticast destination.

- The two cost are different:
- Minimum total cost multicast tree:
- Minimum cost from source to
**any**multicast destination:This type of multicast trees is usually called "minimum delay" trees or "Shortest Path Trees" (SPT).

- The problem of finding the
**minimum cost**multicast tree is known as the**minimum Steiner tree**problem and it is NP-completeWe will not discuss Steiner trees because

- This is not a class on computer algorithms
- more importantly, none of the existing multicast route construction algorithm uses Steiner trees...

- You will see that in both types of multicast tree forwarding algorithm, some form of minimum delay tree will be used.