Determining the Geographic Location of Internet Hosts

1
Determining the Geographic Location of Internet
Hosts

• Venkata N. Padmanabhan
• Microsoft Research
• Lakshminarayanan Subramanian
• University of California at Berkeley
• SIGMETRICS 2001

2
Background

• Location-aware services are relevant in the
  Internet context too
• targeted advertising
• event notification
• territorial rights management
• Existing approaches
• user input burdensome, error-prone
• whois manual updates, host may not be at
  registered location
• Goal estimate location based on client IP
  address
• challenging problem because an IP address does
  not inherently indicate location

3
IP2Geo

• Multi-pronged approach that exploits various
  properties of the Internet
• DNS names of router interfaces often indicate
  location
• Network delay tends to correlate with geographic
  distance
• Hosts that are aggregated for the purposes of
  Internet routing also tend to be clustered
  geographically
• GeoTrack
• determine location of closest router with
  recognizable DNS name
• GeoPing
• use delay measurements to triangulate location
• GeoCluster
• extrapolate partial IP-to-location mapping
  information using cluster information derived
  from BGP routing data

4
GeoPing

• Delay-based triangulation is conceptually simple
• delay ? distance
• distance from 3 or more non-collinear points ?
  location
• But there are practical difficulties
• network path may be circuitous
• transmission and queuing delays may corrupt delay
  estimate
• one-way delay is hard to measure
• GeoPing
• delay is measured from several distributed probes
• minimum delay among several samples is picked
• Nearest Neighbor in Delay Space (NNDS) algorithm
• construct a delay map containing (delay
  vector,location) tuples
• given a delay vector, search through the delay
  map for closest match
• location corresponding to the closest match is
  our location estimate

5
Validation of Delay-based Approach
Delay tends to increase with geographic distance
6
Impact of the Number of Probes
Highest accuracy when 7-9 probes are used
7
GeoCluster

• Basic idea
• divide up the space of IP addresses into clusters
  using BGP prefixes
• use partial IP-to-location mapping data to infer
  location of each cluster
• given target IP address, find matching cluster
  via longest-prefix match.
• location of the matching cluster is our estimate
  of host location
• Issues
• partial IP-to-location mapping information may
  not be entirely accurate
• BGP prefixes might not correspond to geographic
  clusters
• Sub-clustering algorithm
• use partial IP-to-location mapping information to
  test whether a BGP prefix is likely to correspond
  to a geographic cluster
• if the test is negative, divide the prefix into
  two and recursively apply the test to each half
• in the end we are only left with geographically
  clustered prefixes
• dispersion offers an indication of the accuracy
  of a location estimate

8
Performance of IP2Geo
Median error GeoCluster 28 km,GeoTrack 102 km,
GeoPing 382 km
9
Summary

• IP2Geo combines several techniques that leverage
  different sources of information
• GeoTrack DNS names
• GeoPing network delay
• GeoCluster address aggregates used for routing
• Median error varies between 20 and 400 km
• Even a 30 success rate is useful especially
  since we can tell when the estimate is likely to
  be accurate
• Forthcoming paper at SIGCOMM 2001
• For more information visit http//www.research.mi
  crosoft.com/padmanab/