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The minimum RTT shown in Figure 2, is distance dependent. The RTT to North America is artificially low as the measurements are made from North America.
The large step for S. Asia in 2003 was due to the change over from satellite to fibre. as the result of gradual shift from Satellite to fiber. Central Asia (also Afghanistan) has hardly moved in its minimum RTT since it continues to use geostationary satellites. . Africaand S. E. Asia are improving. Central Asia on the other hand has been stuck with geo-stationary satellites and so little change is seen for it. Latin America took a huge step down in RTT at the end of 1999 going from mainly satellite (>500ms) to 200ms (i.e. mainly landlines). S.E. Asia looks like a gradual improvement. For most of the other regions the improvements are marginal.