We present two new results about vertex and edge fault-tolerant
spanners in Euclidean spaces.
We describe the first construction of vertex and edge
fault-tolerant spanners having optimal bounds for maximum degree
and total cost. We present a greedy algorithm that for any t > 1
and any non-negative integer k, constructs a k-fault-tolerant
t-spanner in which every vertex is of degree O(k) and whose
total cost is O(k
2) times the cost of the minimum spanning tree;
these bounds are asymptotically optimal.
Our next contribution is an efficient algorithm for constructing
good fault-tolerant spanners. We present a new, sufficient
condition for a graph to be a k-fault-tolerant spanner. Using
this condition, we design an efficient algorithm that finds
fault-tolerant spanners with asymptotically optimal bound for the
maximum degree and almost optimal bound for the total cost.