Improved Approximation for Single-Sink Buy-at-Bulk

Improved Approximation Algorithms for the Single-Sink Buy-at-Bulk Network Design Problems

Cost-Distance: Two Metric Network Design

We present the COST-DISTANCE problem: finding a Steiner tree which optimizes the sum of edge costs along one metric and the sum of source-sink distances along an unrelated second metric. We give the first known randomized approximation scheme for COST-DISTANCE, where is the number of sources. We reduce several common network design problems to COST-DISTANCE, obtaining (in some cases) the first ...

Single-Sink Network Design with Vertex Connectivity Requirements

We study single-sink network design problems in undirected graphs with vertex connectivity requirements. The input to these problems is an edge-weighted undirected graph G = (V, E), a sink/root vertex r, a set of terminals T ⊆ V, and integer k. The goal is to connect each terminal t ∈ T to r via k vertex-disjoint paths. In the connectivity problem, the objective is to find a min-cost subgraph o...

A Constant-Factor Approximation Algorithm for the Multicommodity Rent-or-Buy Problem

We present the first constant-factor approximation algorithm for network design with multiple commodities andeconomies of scale. We consider the rent-or-buy problem, a type of multicommodity buy-at-bulk network design in which there are two ways to install capacity on any givenedge. Capacity can be rented, with cost incurred on a per-unit of capacity basis, or bought, which allows u...

A Constant Factor Approximation for the Single Sink Edge Installation Problem

We present the first constant approximation to the single sink buy-at-bulk network design problem, where we have to design a network by buying pipes of different costs and capacities per unit length to route demands at a set of sources to a single sink. The distances in the underlying network form a metric. This result improves the previous bound of O(log |R|), where R is the set of sources. We...