Abstract. Discovering router-level IPv6 topologies is important to understanding IPv6 growth, structure, and evolution and relation to IPv4. This work presents a fingerprint-based IPv6 alias resolution technique that induces fragmented responses from IPv6 router interfaces. We leverage the way in which IPv6 implements fragmentation to provide reliable inferences. We demonstrate perfect alias resolution accuracy in a controlled environment, and on a small subset of the production IPv6 Internet for which we have ground-truth. Internet-wide testing finds that over 70% of IPv6 interfaces probed respond to the test. Our promising results suggest a valuable technique to aid IPv6 topology discovery.

Impediments to resolving IPv6 router aliases have precluded understanding the emerging router-level IPv6 Internet topology. In this work, we design, implement, and validate the first Internet-scale alias resolution technique for IPv6. Our technique, speedtrap, leverages the ability to induce fragmented IPv6 responses from router interfaces in a particular temporal pattern that produces distinguishing per-router fingerprints. Our algorithm surmounts three fundamental challenges to Internet-scale IPv6 alias resolution using fragment identifier values: (1) unlike for IPv4, the identifier counters on IPv6 routers have no natural velocity, (2) the values of these counters are similar across routers, and (3) the packet size required to collect inferences is 46 times larger than required in IPv4. We demonstrate the efficacy of the technique by producing router-level Internet IPv6 topologies using measurements from CAIDA's distributed infrastructure. Our preliminary work represents a step toward understanding the Internet's IPv6 router-level topology, an important objective with respect to IPv6 network resilience, security, policy, and longitudinal evolution.