Approximate Distributed Bellman-Ford Algorithms

Routing algorithms based on the distributed Bell-man-Ford algorithm (DBF) suffer from exponential message complexity in some scenarios. We propose two modifications to the algorithm which result in a polynomial message complexity without adversely affecting the response time of the algorithm. However, the new algorithms may not compute the shortest path. Instead, the paths computed can be worse than the shortest path by at most a constant factor (3). We call these algorithms approximate DBF algorithms. The modifications proposed to the original algorithm are very simple and easy to implement. The message complexity of the first algorithm, called the multiplicative approximate DBF, is O(nmlog(nΔ)) where Δ is the maximum length over all edges of an n-nodes m-edges network. The message complexity of the second algorithm, called the additive approximate DBF, is O(Δ/δnm) where δ is the minimum length over all edges in the network. © 1994 IEEE.