Owen Smith wrote: 
> Windows by default ignores a TTL of zero and will cache the IP address
> anyway. Windows DNS caching assumes that DNS to IP address mappings
> hardly ever change.

I'm intrigued by all this. LMS does it's own DNS caching - if you enable
network.asyncdns debug logging you can see that the TTL is mostly set to
20s for the akamai DNS lookups, and external DNS lookups are only made
when that expires. Looking now, the IP address is mostly the same but
does change every so often - I guess that's because things are pretty
quiet now. When I looked earlier on today I was seeing frequent changes
- but still with TTL around 20s, with occasional dips down to 10s. What
I haven't seen is zero TTL, but I guess this might occur during very
busy times.

Using wireshark on a win7 PC earlier today also showed DNS lookups going
out externally every 20s or so, so windows wasn't caching anything
itself.

I've also just tried changing to the limelight CDN - search/replace
uk/sbr_high/ak/ with uk/sbr_high/llnw/ in menu.opml. The primary lookup
domain as-hls-uk-live.bbcfmt.vo.llnwd.net has TTL of 169 seconds, but
redirects to a different domain name for every HLS chunk with no repeats
obvious - so DNS lookups for every single HLS chunk. This is a much
worse situation than with the akamai streams, but those DNS lookups
complete in under 1/10th of a second on my network connection by the
looks of it, so there is no problem at all with the playing.


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