Simple path queries on large graphs

I have a question about large graph data. Suppose that we have a large graph with nearly 100 million edges and around 5 million nodes, in this case what is the best graph mining platform that you know of that can give all simple paths of lengths <=k (for k=3,4,5) between any two given nodes. The main concern is the speed of getting those paths. Another thing is that the graph is directed, but we would like the program to ignore the directions when computing the paths but still return the actually directed edges once it spots those paths.

For instance:

a -> c <- d -> b is a valid path between nodes 'a' and 'b' of length 3.

Thanks in advance.