[dns-operations] opting in to stupid DNS tricks

Simon Lyall simon at darkmere.gen.nz
Mon Feb 21 19:41:15 UTC 2011


On Mon, 21 Feb 2011, Jim Reid wrote:
> BTW, I still don't understand why CDNs are abusing the DNS to solve something 
> that is actually a routing problem. What's wrong with anycasting the IP 
> address(es) of the web site or whatever? That way, the network figures out 
> the truly optimal path (peering policies aside) between the end client and 
> the content provider's server.

Hi, my name is Simon and I use GSLB on my [company's] website.

For me the simple answer to your question is cost. I have customers in 
parts of the world and I want to server their packets from 
closer since it is cheaper and they get a better experience.

Here is the specs of a website around the same size as me:

http://blog.serverfault.com/post/stack-exchanges-architecture-in-bullet-points/

You will note that these guys problem don't own their own IP space, they 
just get from their providers.

Lets say they have enough customers around the world that they decide to 
speed up their service. So they buy a machine in Australia, Europe, 
Singapore and the UK and run some caching software (varnish say) on them.

Cost $1,000 / month

and then they setup GSLB in-house or buy from a provider [1] :

Cost $0 - 1500 / month  [2]

and it pretty much just works.

With anycast on the other hand the big problem is that besides the 
overhead complexity of implementing it [3] I can't just buy a "Anycast 
Server" from a provider via a web-form and a credit card for 
$100-$250/month[4].

I've gone from semi-commodity product to a sales guys, special network 
setup etc. Now *maybe* I can do this for $1000/month/pop but I really 
doubt it.

Also GSLB gives me a lot of flexibility. Keeping the same URLs I could 
move all my European traffic over to a local CDN provider very easily or 
buy a bit of space on a "Pay for usage, minimal monthly" CDN provider and 
only use them in emergencies.

If I was building $1 million + $100k/month Pops around the world then 
then going anycast would gut lost in the noise but outside the "Big boys" 
and people providing DNS services[5] anycast isn't a realistic option.

Oh and I build me own servers rather than go with a CDN provider because 
(a) It's cheaper at my traffic level and (b) There are only two CDNs with 
New Zealand POPs, Akamai and I tried the other.

[1] I used 3crowd.com, highly recommend
[2] $1500 is what I got quoted by one GSLB provider. Others were
     significantly cheaper
[3] With GSLB I just delegate the DNS record and then I have a cute
     dashboard where I fill in the IPs of my servers
[4] I just typed "anycast" into google and didn't get any ads. Bad sign
[5] Like GSLB providers.

-- 
Simon Lyall  |  Very Busy  |  Web: http://www.darkmere.gen.nz/
"To stay awake all night adds a day to your life" - Stilgar | eMT.



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