Custom Domain Instability Caused By Using Unacceptable Servers

A few blog owners become confused by the necessary configuration of the domain root, when setting up their custom domains.

Some blog owners, who do not have a good understanding of DNS principles, make mistakes when setting up the domain root (aka "naked" domain). From good intentions (trying to ensure that the domain performs better or differently), their naivete may actually make the domain perform worse - or not at all.

With more blog owners unable to buy a domain through Blogger, and forced to setup their own DNS addresses, this will become an increasingly critical issue.

Blogger designed the custom domain feature to use "A" / "CNAME" referral, instead of DNS / frame forwarding.

The most obvious referral configuration - dual "CNAME" aka "symmetrical" DNS - is not supported by all registrars. Some registrars refuse to allow "CNAME" definition of the domain root, by policy.

To make custom domain publishing more globally usable, Blogger provided an alternative to dual "CNAME" referral - a hybrid configuration which uses 4 x "A" referral, for the domain root. This configuration is also known as "asymmetrical" DNS.

Asymmetrical DNS uses 4 Google servers, accessed in a round robin sequence, to define the domain root.

mydomain.com.  3600 IN A 216.239.32.21
mydomain.com.  3600 IN A 216.239.34.21
mydomain.com.  3600 IN A 216.239.36.21
mydomain.com.  3600 IN A 216.239.38.21
www.mydomain.com. 3600 IN CNAME ghs.google.com.

Round robin DNS is pretty simple. Each server in the set is queried by the DNS client on the readers computer, in sequence, until one server responds. The first responding server is required to provide a suitable answer. If the first responding server provides an unsuitable answer, the DNS client has no alternative but to display yet another version of

Server Not Found
Error 404

Google uses the 4 servers to provide quadruple redundancy. One server is designed to handle the entire workload, at any time - with 4 servers, and each server running at 25% of full load. If any one server has to be temporarily taken out of service, they still have 3 servers - with each server running at 33% of full load.

During scheduled maintenance - and with triple redundancy, even two simultaneous emergencies (with 2 servers out of service, unscheduled) will not cause an immediate, major problem. This allows Google Engineers to schedule routine network maintenance as mutually convenient for everybody in their group - even considering the global need for Blogger services, on a 3600 x 24 x 7 x 56 basis.

There is one weakness of round robin DNS. All servers, in the set, have to be equally capable of performing reliably. A naive blog owner, including any additional or different server, in the set, risks having one server, responding to the round robin access - but providing an unsuitable answer.

mydomain.com.  3600 IN A 50.63.202.39
mydomain.com.  3600 IN A 216.239.32.21
mydomain.com.  3600 IN A 216.239.34.21
mydomain.com.  3600 IN A 216.239.36.21
mydomain.com.  3600 IN A 216.239.38.21
www.mydomain.com. 3600 IN CNAME ghs.google.com.

What is 50.63.202.39?

ip-50-63-202-39.ip.secureserver.net (50.63.202.39)

50.62.0.0 - 50.63.255.255
GoDaddy.com, LLC GO-DADDY-COM-LLC (NET-160-153-0-0-1) 160.153.0.0 - 160.153.255.255

GoDaddy uses forwarding - not referral - to direct traffic. Here, some (not all, and not always) prospective blog readers see

Server Not Found
Error 404

Some blog owners make a second mistake - which compounds the first mistake.

mydomain.com.  3600 IN A 50.63.202.39
mydomain.com.  3600 IN A 216.239.32.21
mydomain.com.  3600 IN A 216.239.34.21
mydomain.com.  3600 IN A 216.239.36.21
mydomain.com.  3600 IN A 216.239.38.21
www.mydomain.com. 3600 IN CNAME mydomain.com.

Here we see the "www" alias - which is what 95% of your direct traffic accesses - using the domain root for obtaining the address. Add to that the bogus server (in this example, "50.63.202.39"), and you will get a lot of complaints about sporadic connectivity problems.

Server Not Found
Error 404

This is so simple - if you only believe.

mydomain.com.  3600 IN A 216.239.32.21
mydomain.com.  3600 IN A 216.239.34.21
mydomain.com.  3600 IN A 216.239.36.21
mydomain.com.  3600 IN A 216.239.38.21
www.mydomain.com. 3600 IN CNAME ghs.google.com.

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