Terry Slattery the founder of Netcordia brought to my attention an interesting tool called the Paris traceroute that was developed by students and professors with funding from the Centre National de la Recherche Scientifique in Paris. According to the tool's Web site, Paris traceroute addresses some of the limitations of traceroute, the well-known network diagnosis and measurement tool.
According to the developers, Paris traceroute addresses problems caused by load balancers with the initial implementation of traceroute. Traceroute fails in the presence of routers that employ load balancing on packet header fields, say the developers. Paris traceroute, by controling packet header contents, obtains a more precise picture of the actual routes that packets follow, the developers claim.
Perhaps the following taken from the Paris traceroute site will help pique your curiosity to learn more...
A brief demonstration of Paris traceroute's skills:
Suppose above you are trying to measure the route between Src and Dst. The true router topology is shown on the left. L is a router that balances load on two paths, via routers A or C. The middle of the figure shows what you might see with classic traceroute. The right part is what you would get with Paris traceroute...
Traceroute's deficiencies under load balancing:
In the example above, L is a load balancer at hop 1 from the traceroute source. The true router topology from hops 1 through 4 is shown on the left. Routers are represented as circles and each of their interfaces is numbered. Also shown are the probe packets sent with TTL 1 to 4. The packets are depicted as yellow arrows, either above the topology, if L directs them to A, or below, if L directs them to B. At the right side, the topology is presented that would be inferred given these probe packets.
Summary of the IP, UDP, and ICMP header fields that are used by load balancers, classic traceroute, and Paris traceroute:
Above are the IP, UDP and ICMP headers. Per-flow load balancers use the grey fields to identify a flow. Red arrows show the fields incremented by classic traceroute. Paris traceroute uses the green fields to identify probes.
Have YOU used the Paris traceroute tool or come across other improvements on traceroute to share?
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