2. Doubletree: a Way to Reduce Redundancy in Traceroute Systems Benoit Donnet joint work with P. Raoult, T. Friedman and M. Crovella CAIDA – San Diego (Sept. 2005)

3. Context ● Network measurement ● Internet topology discovery using distributed traceroute monitors – IP interface level ● Existing tools: – Skitter (CAIDA) – TTM (RIPE NCC) – AMP (NLANR) – DIMES (Tel Aviv U.)

4. Problem: Intra-Monitor Redundancy

5. Problem: Inter-Monitor Redundancy

6. Statement ● Classical approaches are out of date ● Wide scale deployment of traceroute tools – DIMES ● Scale up the number of monitors – little work on efficiency ● Be careful regarding – network resources – load on destinations

7. Doubletree: Basics ● Cooperative algorithm ● Goal: avoiding paths already explored ● Exploits tree-like structure of routes in the internet: – from a monitor to a set of destinations: ● monitor-rooted tree – from a set of monitors to a destination: ● destination-rooted tree

8. Doubletree: Monitor-Rooted Tree

9. Doubletree: Destination-Rooted Tree

10. Doubletree: Reconciliation ● Backward and forward probing are opposite schemes ● How can we reconcile them? – Starts probing at some hop h ● First, forward probing from h ● Second, backward probing from h-1 ● How to choose h? – Probability p of hitting a destination with the very first probe sent

11. Doubletree: Reconciliation (2)

12. Doubletree: Stop Sets ● Not necessary to maintain the whole tree structure. ● Each monitor uses stop sets: {(interface, root)} – Local Stop Set B: {interface} ● Backward probing – Global Stop Set F: {(interface, destination)} ● Forward probing ● Shared between monitors ● Could be implemented as Bloom filter

13. Doubletree: Coverage

14. Doubletree: Redundancy

15. Doubletree: Amount of Probes

16. Doubletree: Implementation

17. Future Works ● Improvement to Doubletree – Reducing the amount of probes sent ● Capturing the dynamicity of the network ● BGP-guided probing ● Overlay/P2P structure organizing the whole system ● Measurement tools standardization

18. Conclusion ● Doubletree is an efficient and cooperative algorithm allowing – redundancy reduction – good coverage level ● Java implementation of a prototype