Some people may be using a browser which is more forgiving of DNS problems than others - and people who use the right browser, when accessing a domain with righteous DNS addresses, should expect to generally get more consistent service. But that's only a small part of the story.
DNS is the basis for custom domain publishing - and DNS is used in a number of ways. This creates a number of bases for inconsistencies.
- Inconsistencies From The Browser
- Inconsistencies From Individual DNS servers
- Inconsistencies From Large ISP DNS Servers
- Inconsistencies From The Google Name Servers
- Inconsistencies From WorldWide DNS Services
- Inconsistencies From The WorldWide Internet Infrastructure
Some browsers, if they have a problem getting an IP address for the domain root (using the 4 x "A" servers) may automatically use the "www" alias.
If your domain provides only 1 x "A" address, it may be more susceptible to problems, when this aliasing of the domain root and "www" host are in use - since an outage which involves 1 "A" server may be more common than an outage which might involve all 4 x "A" servers simultaneously.
If your domain is not setup with both the domain root and "www" host properly addressed - or if the domain root to "www" host redirect is not enabled, the domain may not perform consistently.
Individual DNS servers
No people (you, or your readers) access the domain registrar's servers directly, to get the address of your domain. You use "local" DNS servers - the DNS severs provided by your ISP (or maybe a custom third party service like like GoogleDNS or OpenDNS). The "local" DNS servers that you use retrieve DNS addresses from the "authoritative" DNS servers provided by the registrar. The registrar servers reference the 4 x "A" / "CNAME" servers, provided by Google, using "referral", to get the address of your blog.
The servers that you use only access the registrars servers periodically, thanks to DNS cache. That's the mysterious TTL, which your domain's authoritative DNS servers specify. If the address for your domain is in cache, on any local DNS server, and cache is not expired (the address was retrieved any time in the previous TTL period) the local DNS server that you use simply issues what it already has.
Since almost every different reader of your blog uses a different "local" DNS server, you're going to see inconsistency in problem reports, from your readers.
Large ISP DNS Servers
If your domain is popular, people accessing your domain from a large ISP - or an ISP that is close to you geographically (if your readers are geographically concentrated) - is more likely to have the DNS addresses, for your domain, in cache. In this case, no retrieval from the registrar's servers will be necessary. The higher the TTL, the greater the chance this will be the case.
The Google Name Servers
If your readers are accessing your domain using the "www" alias, they are using the "ghs.google.com" name server for accessing your blog. The design of "ghs.google.com" means that everybody on the Internet, accessing any Blogger blog published to a custom domain, uses the same DNS addresses, cached locally. This too means that large ISPs - who are more likely to have somebody (if not you) accessing some Blogger blog published to a custom domain - are more likely to have the address for your blog in cache.
Your blog, and your domain, are addressed separately, and require separate DNS servers. This is why a righteously addressed domain uses "CNAME" referral, when mapping your domain to your blog. And this is why you have to purchase (or setup) DNS hosting, when you register your domain.
WorldWide DNS Services
Some of the 4 x "A" and "CNAME" servers, provided by Google, are not completely unique. Many large DNS infrastructures - like those provided by eNom, GoDaddy, and Google - have "unique" IP addresses replicated worldwide, using "Anycast DNS". This feature can sometimes create regionally concentrated outages, with some domains - as we have seen periodically, with eNom.
The WorldWide Internet Infrastructure
The combinations of browser used, domain popularity, ISP size (customer population), and regional outages, will always cause discrepancies between domains, and people in different locations and using different ISPs. What you (one person) see, where you are, may be completely different from what one of your readers (or my readers) sees, when using a different ISP, in another country, and a different browser.
Thanks to the transient nature of IP networking, you may "test" or observe problems over minutes or hours - but many DNS problems can appear and disappear in seconds. That''s in spite of what you would expect from cache / TTL latency.
All of these seemingly insignificant details, when fully understood, may help to explain why I continually insist on using righteous DNS addresses, whenever a custom domain publishing problem is encountered. Righteous addresses won't necessarily solve all of the above problems - but it may eliminate some of the inconsistencies, and make it possible that we could, eventually, diagnose the problem.