While I agree that a Graph is the best way to go, if you are pretty sure that the routes remain fixed, you could also easily use a tree structure; each node has an array of children, the top node being your target IP that you're tracerouting too. For each traceroute, from the target back, start at the top of the tree, and if the next IP exists as a child, move to that node and do the next IP. If the IP doesn't exist as a child, create a new one, attach to your current node, then move down into that and repeat from there (of course, you'll be making new nodes all down to your final IP from that).

Again, there might be problems with cycles resulting from this, depending on when routes change, etc. and the speed at which you collect the tracerouts.

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Dr. Michael K. Neylon - mneylon-pm@masemware.com || "You've left the lens cap of your mind on again, Pinky" - The Brain
It's not what you know, but knowing how to find it if you don't know that's important