In March 2004, one of our suppliers had a power problem at their datacentre which necessitated turning off the power to one of our POPs. Customers were mostly unaffected (they were able to login through one of our other POPs after they were kicked-off the one that went down), but the outage did significantly change the traffic flows around our network:
The bright red lines indicate links which are down (congested links are also shown red, but not as bright. There aren't any in this example). The yellow link between Canberra and Sydney has occurred because some of the traffic between Sydney and Adelaide was forced to go via Melbourne and Canberra, which pushed that link past 85%. The grey link between Sydney and Hobart occurred because the router which that link terminates on was down, so Nodemap was unable to gather data and marked the status of the link as "indeterminate".
And yes, we have upgraded the Perth link since the outage, which is why the "before" and "after" pictures are inconsistent.
The map shows a relatively complex metropolitan topology, with five POPs linked together with redundant fibre circuits, with multiple peering and transit links at each POP.
The screenshot also demonstrates the transparency feature: The image was captured while the mouse pointer (which isn't shown) was hovering over one of the links. A beige popup window has appeared to give detailed info about the link, but the map can still be seen "behind" the transparent popup.
Here's what the same map looked like during the outage described above. Note the red links: They're the reason why the "Sydney" blob in the top-level map was red instead of its usual green:
The grey, yellow and red links clearly show what's going on. A single glance is all that's needed to obtain a fairly detailed view of the network status.