It's not illegal to have TTL that short but it certainly feels like violation of some implicit contract between users and provides. Of course the root cause of this is the horrendous hack of using DNS for CDN routing. It doesn't have to be that way... I wrote a recent article about this very issue here
I haven't heard of packetzoom before, I'll definitely take time over the weekend or next week to dig into your approach.
I wouldn't call DNS based IP mapping "horrendous" simply because it doesn't work as well for mobile,I understand you have your own pitch but lets go easy on the hyperbole :)
The fact is that it is still very effective. The major CDNs are quite aware of the mobile shortcoming of DNS based mapping and I am pretty sure it is something they are working to address.
At the end of the day location is just one component involved in accelerating content, there are plenty of other features that various CDNs use to deliver optimal performance.
Regarding the short TTLs, I get your argument, it is indeed like a user's browser is constantly chasing a moving origin. The alternatively however is a non-optimized web, which would be orders of magnitude worse. Remember the benefits of CDNs doesn't just accrue to end users but also to content providers, most origin servers can't handle even the slightest up tick in traffic.
"I wouldn't call DNS based IP mapping "horrendous" simply because it doesn't work as well for mobile"
OK I'll take back the word "horrendous" but it's a hack alright.
> The fact is that it is still very effective. The major CDNs are quite aware of the mobile shortcoming of DNS based mapping and I am pretty sure it is something they are working to address.
No not really. They're certainly trying to patch DNS to pass through enriched information in DNS requests through recursive calls... but it's such a long shot to work consistently across tens of thousands of networks around the world, and requires coordination from so many different entities, that it's clearly a desperation move more than than a serious effort. Regardless, there's no real solution in sight for the web platform.
For mobile (native) apps though, the right way to discover nearby servers is to directly build in that functionality using mobile specific techniques. There's no reason to keep limiting mobile apps to old, restrictive web technologies considering that apps have taken over as majority of traffic around the world. That's the root idea behind a lot of what we're doing at PacketZoom. Not just in service discovery, but also in more intelligent transport for mobile with built-in knowledge of carriers and network technologies etc, automatic load-balancing/failover of servers and many other things. Here's my older article on the topic
http://www.infoworld.com/article/3133104/mobile-technology/w...