[vishnugupta]

I understand how CDNs are advantageous by having contents served from locations that are closer to origin of requests (typically browsers spread across the world or a country etc.,).

However, for DNS service to be of similar use does it mean application servers are going to be spread across geographically? For end customers it doesn't matter as they will always use the DNS configured for them by their ISP in most of the cases unless one is tech savvy and tries to use some other DNS such as Google etc.,?

Please help understand what am I missing here?

[tedivm]

You're an Australian Internet User. You want to see hampsterdance.com 'cause fuck it, you like hamsters.

Your computer asks your ISP's DNS server for the record. If your ISP has it cached you're golden, but it turns out it probably isn't. So your ISP needs to go to ask the hampsterdance.com DNS server directly. If that server is in the United States then you're stuck waiting 133ms in one direction, 133ms back- you've now added a quarter of a second to that page loaded.

Using a DNS CDN means that 266ms ends up being 15ms (keep in mind that these guys also peer with local ISPs to make things even faster).

[BorisMelnik]

Thank you very much for this explanation. So for example I have a very basic website with CMS. I use a CDN just because I want to give the best possible experience to my users. I get about 50k users per month, a lot of them are new. Would adding a paid DNS or "DNS CDN" as you put it help my user experience enough to matter?

[tedivm]

Honestly it depends on who your market is. If your users are mostly on the same continent as you it's probably not worth it, otherwise it could be.

On the other hand, if your site makes you money and you've got competition then every edge you can get is worth while.

[BorisMelnik]

thank you and thank you. ok that really makes sense. my site is b2b and although transactions do not occur on the website every ounce of frustration I can save matters. we also get a ton of users from US/AU/EU/AS so even with that it would make sense.

[BorisMelnik]

also DNS newb question here: is a query essentially an HTTP request?

[tedivm]

Similar concept, different protocol. DNS is much more lightweight than HTTP, and also tends to run over UDP instead of TCP.

[scott_karana]

You're point is solid, but can you clear up some confusion for me? I'm not sure whether:

1) Round-trip times from Australia to the USA are truly as bad as 266ms

2) You're confusing ping's RTTs with one-way trips

3) You're assuming DNS has a syn/ack, which it doesn't.

EDIT: I suspect you realize there's no syn/ack in DNS based on your other comments... :)

[squeaky-clean]

I live on the east coast of the USA. Speedtest.net says my ping to my nearest server is 26ms, and to Sydney is 259ms. So it seems it really is that bad.

[tedchs]

When we say "bad", let's remember that that's very close to the speed of light through fiber.

[scott_karana]

Thanks! That's depressing. :(