  Our motivation is to improve on the best approximation guarantee known for
the problem of finding a minimum-cost 2-node connected spanning subgraph of a
given undirected graph with nonnegative edge costs. We present an LP (Linear
Programming) relaxation based on partition constraints.
  The special case where the input contains a spanning tree of zero cost is
called 2NC-TAP. We present a greedy algorithm for 2NC-TAP, and we analyze it
via dual-fitting for our partition LP relaxation.
  Keywords: 2-node connected graphs, approximation algorithms, connectivity
augmentation, greedy algorithm, network design, partition relaxation
