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Showing posts with label Custom Domains Schizophrenia. Show all posts
Showing posts with label Custom Domains Schizophrenia. Show all posts

Monday, 14 October 2013

Why Do We Need Four DNS Servers?

Occasionally, we see a perplexed blog owner asking a popular question about custom domain setup.
Does my domain really need four servers?
Some even seem to think that newer domains, with less readers, can get by with less - even one - servers.

Won't one server do - at least, for newer blogs? Theoretically, yes. But not one server is going to be 100% reliable, or last forever. Every computer ever made, like every human born, will die, one day.

Your blog (and your domain) depends upon DNS, to resolve its address. Address resolution is an essential part of helping your computer connect with the computer where your blog is stored.

If you specify just one server for your domain, and that one server goes down, your domain will be out of service - to the people depending upon that one server.

The named DNS server "ghs.google.com" is a redundant server array.
www.mydomain.com. 3600 IN CNAME ghs.google.com.

We use a "CNAME" to reference "ghs.google.com" - and we can't always use a "CNAME". Most registrars will not let you use a "CNAME" to resolve the domain root.

Google provides the 4 x "A" addressed server set, to resolve the domain root - when you wish to simply redirect the domain root to one of the aliases. Most domain owners will redirect the root to the "www" alias - though you are allowed to redirect to any one alias, at your discretion.

Google provides four mutually redundant individual servers, each responding to a specific IP address, for custom domain clients to access in a round robin sequence.

If any one server in the array of four becomes overloaded or goes out of service, and doesn't respond to a DNS query, the DNS resolver, on any client computer, will try the next server defined - if there is another server provided. If your domain provides just one server to resolve its address, and that one server goes down, your domain goes out of service. Your readers will see, yet again
404 Server Not Found
But wait - - there's more. Since Google provides four servers, and only one is out of service, they won't regard that as a major emergency. They still have three servers online - and nobody is losing sleep. Except, of course, you.

Google will repair or replace their one down server, when it is convenient to them. Maybe that will be next week, when their DNS server technician gets back from vacation.

Is that not convenient to you? Sorry.

With an asymmetrical configuration, you may not publish to the domain root. Your only valid choice is to publish to "www.mydomain.com", and select "Redirect mydomain.com to www.mydomain.com". If you publish to "mydomain.com", you will eventually see
Another blog is already hosted at this address.
or
Blogs may not be hosted at naked domains.

If you want to publish your blog to a custom domain using an ASymmetrical configuration, always publish to "www.mydomain.com", not to "mydomain.com". If you want to publish to "mydomain.com", you'll have to use a Symmetrical DNS configuration, and risk losing services hosted by your registrar. If you go with the first option, you will need all 4 servers - if you want a reliable and supported custom domain.

If your registrar or hosting service does not support 4 x "A" DNS addresses setup, you may want to use a (free) third party DNS host. Now, here's hoping that your registrar allows easy configuration of third party DNS service.

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Tuesday, 25 June 2013

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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Friday, 12 October 2012

Schizophrenia And Custom Domain URLs - October 2012

Now that the custom domain publishing feature is back online again, there remains one feature of custom domain publishing to be restored to the Blogger dashboard.

The very popular Blogger dashboard option to redirect the domain root (aka "naked domain"), to the "www" alias, may not be reliable - or even available.

Too many people report
I can't redirect the naked domain - I can select the option, but the next time I look, the box will be un checked.
and
My "www" alias works just fine - but the domain root now returns a "404".

Fortunately, there are alternative solutions to provide the naked domain redirect.

There are 3 ways to redirect the domain root to the primary ("www" - or any alternate selection) alias.
  • Registrar Domain Manager forwarding.
  • Blogger Publishing redirect.
  • Google Apps "Domain settings" redirect.


The Registrar Domain Manager provides, for some blog owners, the currently most obvious alternative to the Blogger Publishing redirect - but it is not the simplest to use. Depending upon the registrar, and the nature of the domain manager / DNS servers, this procedure may not even work.

Some registrars will recommend simple DNS or frame forwarding to the BlogSpot URL - and this "solution", we know from experience, will not work at all. One problem here will be spurious spam classification, caused by what looks like an offsite redirect of the domain root.

The Blogger Publishing redirect option, which currently may not work consistently, is normally the most obvious alternative. This is, however, the preferred option, in custom domain publishing - and re publishing - procedures.

A less obvious option, the Google Apps "Domain settings" redirect option, is currently the best solution. For any newly purchased domain - as well as for domains purchased directly from a registrar, it's possible (though currently, with some effort) to setup a Google Apps domain administrator account. Next, use the "Change how your naked domain is redirected" screen, and change or recycle the domain root redirect.

Which ever alternative you chose - or made to work, the domain root should now redirect to the alias of your choice.

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