Optimal cache placement for an academic backbone network

Deploying caches on a network is an effective way to reduce the amount of data transmitted in a network. Recently, in an academic backbone network such as SINET (the Science Information Network) in Japan, the amount of transmitted data has signi(cid:12)cantly increased. It is desired to design an efficient mechanism to allocate caches in an optimal way. In this paper, we begin by formulating a discrete optimization model to (cid:12)nd a cache allocation that minimizes the total transmission cost. We then design two efficient algorithms to solve our proposed model. The (cid:12)rst one makes use of the fact that a backbone network has small treewidth. The algorithm runs in polynomial time when the number of items is (cid:12)xed and a graph has a bounded treewidth. The other one reduces the problem to the minimum-cost (cid:13)ow problem under the practical assumption that each item has at most one copy. This yields a polynomial-time combinatorial algorithm. Our numerical experiments on the real SINET network show that our algorithms can solve the cache placement problem efficiently in practice.