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Japanese hosts seen from JP.RIKEN.N3 (RIKEN) see no impact on RTT
It looks the problem is in the route to Japan not within Japan itself. I wonder if the undersea earthquake has disrupted some cables? This appears to be in line with the information from [http://www.renesys.com/blog/2011/03/japan-quake.shtml|http://www.renesys.com/blog/2011/03/japan-quake.shtml] and [http://www.networkworld.com/news/2011/031411-quake-damage-to-japan-cables.html?source=NWWNLE_nlt_network_architecture_2011-03-15|http://www.networkworld.com/news/2011/031411-quake-damage-to-japan-cables.html?source=NWWNLE_nlt_network_architecture_2011-03-15].
Undersea Cables
A map of the cables from Telegeography is seen below:
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