Large Increase in RTT from South Africa to CERN, April 2006

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Les Cottrell. Page created: May10, 2006

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We analyzed the PingER minimum Round Trip Time (RTT) data seen from the PingER monitoring sites to the various regions of the world looking for remote sites with anomalously large min-RTTs (three standard deviations outside the mean from the monitoring site to sites in the designated region). The table of results indicated anomalous min-RTT (445ms compared to regional average for Europe of 268ms seen from South Africa) from the TENET site in Cape Town South Africa to CERN in Geneva Switzerland. Looking in detail at the PingER min-RTT time series between these sites it is apparent that between April 9 and 10 there was a large step-change increase in the min-RTT.

We used reverse traceroute servers at CERN and South Africa to look in more detail. The traceroutes from CERN to South Africa and vice versa confirmed the large round trip times. We looked at the traceroute from South Africa to DESY and this showe a shorter min-RTT. The CERN-South Africa route was via Abilene in the U.S. while the DESY route was more direct via GEANT.


We emailed CERN and TENET to inform them of our findings. Edoardo Martelli of CERN sent email explaining:
Regarding South Africa, this can explain the change:
Now we've changed the policies with Abilene, and South Africa 
is back to Geant.
Basically after March 22nd Abilene started exchanging traffic with TENET through the MAN LAN international exchange point in New York City.
Page owner: Les Cottrell