It's possible that there is a router between you and this forum's servers that is sending packets into some third dimension, but it's been working quite well for me since the forum's server hardware upgrade a couple of weeks ago.
"sending packets into some third dimension" Well, I think the proof of some third dimension of inverse knowledge is demonstrated daily on this forum, ;-)
While there is probably no way to confirm but some may be gov't systems like for military installations or dedicated trunks. It seems strange to me that some systems can only be access from a particular IP.
I was looking at one in which the only way to get a connection was to be in Korea and was a direct line only to San Jose and then to Dallas and was only visible in one direction. Really strange.
I also wonder how many of these may be due to unknown bugs in the router software. If all the cisco or juniper routers had some bugs it may account for this.
most data packets have a "time limit" that they can exist between point A to B. This question of routing load and packets being "lost" or permitted to expire because of higher "order" packets-------- was studied extensively during the late 80's & 90's------ this lead to the massive optical cable being buried. Then improved modulation increased the about of the packets being carried, then routers and switches improved, the need to rent bandwidth disappeared.
With more complex webpages, BT, Flash files, youtube, facebook, etc. increasing load......... the early model of management is being stressed. Now, we are back to the same question of load management and as in the news about cable companies "reducing uploading bandwidth". Since many packets have a "resend" count, so on a heavy loaded router/switch, a queued package could be easily tossed. If a lower router/switch has also tossed the packet, this could lead to the "black hole" effect.