Efficient Algorithms for Large-ScaleTopology Discovery

Benoit Donnetjoint work with Philippe Raoult, Timur Friedman

and Mark Crovella

Sigmetrics 2005 – Banff (Canada)

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.)

Scaling Problem

● More monitors means more load on– network resources

– destinations

● Classical approaches either– stay small (skitter, TTM, AMP)

– trace slowly (DIMES)

● Can we trace more efficiently?

Contributions

● Quantification of scaling problems– Intra-monitor redundancy

– Inter-monitor redundancy

● Efficient cooperative topology discovery algorithm– Doubletree

Intra-monitor Redundancy (1)

Intra-monitor Redundancy (2)

Inter-monitor Redundancy (1)

Inter-monitor Redundancy (2)

Doubletree: Tree-like Structure of Routes

● Both redundancy (i.e. inter and intra) suggest two different probing schemes– They are based on the tree-like structure of routes

● Intra-monitor– monitor-rooted tree (first suggested by Govindan et al.)

● Inter-monitor– destination-rooted tree

Doubletree: Monitor-rooted Tree

Doubletree: Destination-rooted Tree

Doubletree: Reconciliation

● Backward and forward probing are opposite schemes

● How can we reconciliate them?– Starts probing at some hop h

● First, performing forward probing from h● Second, performing backward probing from h-1

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

Doubletree: Results (1)Intra-Monitor

skitter Doubletree

Doubletree: Results (2)Inter-Monitor

skitter Doubletree

Conclusion

● We point out redundancy in classical topology discovery approaches using two metrics:– Intra-monitor redundancy

– Inter-monitor redundancy

● Based on these metrics, we define the Doubletree algorithm:– Measurement load reduction up to 76%

– Interface and link coverage above 90%