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  • The first test was conducted on 1st July,2008. Here are the results of the test. Here we compared only those results where the same landmarks were used.
  • The second test was conducted on 2nd July,2008. Here are the results of the test. Some quick observations from the tests second test are:
  1. The results are very bad as compared to the previous ones because a lot of landmarks are failing. We are currently thinking on ways to improve on that.
  2. The maximum improvement using floating point was 124 Km.
  3. Stanford_UnitedStates_PL is giving funny results, will have look deeply into it to find out the cause.

Comparing results with old results after careful selection of landmarks

After careful selection of landmarks (removing non-responding landmarks and writing scripts to dynamically generate landmarks) on 20th Aug,1008 we obtained much better results. These results are compared to the old results in order to see the improvements. The results can be download here Here are some quick observations:

  1. Menlo Park Landmark (Stanford) is giving wrong result (rtt 2ms) which is ruining the results. We need to disable this landmark since we already have landmark at SLAC.

  2. There are some major improvements in results due to careful selection of landmarks.

  3. the median error is 170km, 25% 100km, 75% 362km & IQR 262km. This is including the numbers in red.

  4. Need to come up with a method to avoid bad results for replicated servers.

Abnormal Cases:

 Hosts that are on satellite links have very large delays. They cannot be located using the RTTs from a set of landmarks. Usually they have RTTs > 500ms. Most of the Central Asian countries (including Afghanistan) and some African countries use satellite links. Data from hosts in Kazakhistan, Burundi, Madagascar, Uganda, Afghanistan and Nigeria can be found here. The three best Landmarks chosen gives an RTT greater than 500ms. If the RTT from the three best landmarks is greater than 500ms then our algorithm returns the host as satellite link and does not perform trilateration. This figure may be changed latter.

Children Display
pageReplicated Servers

Replicated Servers


 Trilateration VS Multilateration

  Here is the data.