While Google are attempting to be smart by offering DNS services to the globe – this will result in poor perfoamance for users unless they shape things up very quickly!
All CDNs (Content Delivery Systems), including Google, use DNS to decide where to send users to a webpage.
The decisisions done by the CDNs is based on the location to your ISPs DNS server(s). The CDN will look at the DNS servers that are querying its hosting servers, see the latencey and reliability of paths it has from its caches or clusters to that DNS server and pick the closest and fastest cache for that DNS server.
What are Google doing wrong then?
-They don’t have geographic DNS servers.
When I do a query of popular news website hosted by Akamai (another content delivery network), www.news.com.au, I should expect to be directed to a server close to me, this isn’t the case.
C:\Documents and Settings\Tom>nslookup www.news.com.au 8.8.8.8 Server:Â google-public-dns-a.google.com Address:Â 8.8.8.8 Non-authoritative answer: Name:Â Â Â a1273.g.akamai.net Addresses:Â 58.27.186.113, 58.27.186.104 Aliases:Â www.news.com.au, www.news.com.au.edgesuite.net C:\Documents and Settings\Tom>
Now, this couldn’t be so bad could it? Well, yes it could! Lets compare it to the DNS resolution from the ISP.
C:\Documents and Settings\Tom>nslookup www.news.com.au Server:Â P1-REMQIP01-P.p1.com.my Address:Â 122.255.96.148 Non-authoritative answer: Name:Â Â Â a1273.g.akamai.net Addresses:Â 63.150.131.157, 63.150.131.200 Aliases:Â www.news.com.au, www.news.com.au.edgesuite.net C:\Documents and Settings\Tom>
And now lets compare latencey results:
Google Results:
Reply from 58.27.186.113: bytes=32 time=244ms TTL=51
ISP Results:
Reply from 63.150.131.157: bytes=32 time=98ms TTL=55
I won’t go into how TCP Windowing will affect performance here – but the latencey figures should be enough to show!
Google’s FAQ talks about them using Anycast routing to direct you to the closest server, but they’re only announcing the ranges (8.8.8.0/24 and 8.8.4.0/24) out of their US network, so any user reaching them will _have_ to go to the USA which will result in poor performance for the CDNs.
There is also the problem that it takes a quarter of a second to reach the USA from other parts of the world – which also will result in poor performance.
I would have hoped Google should know better than advertise it as something to speed up browsing for users and that they should understand the protocols better.