From the blog "Tools and Technology"

Quite some time ago, we introduced viewer changes that moved the fetching of most assets from using UDP through the simulator to HTTP through our content delivery network (CDN) to improve fetch times and save cycles on the simulator for simulation. At the time, we did not disable the UDP fetching path so that all users would have time to upgrade to newer viewer versions that fully support the new HTTP/CDN path. We warned that at some time in the future we would disable the older mechanism, and t