1. DNS/naked_domain

"naked domain" とは

ドメイン名を短くすることでアクセスしやすくなると考えるようだが、いろいろの害がある。

1.1. DNS の制約

ドメインの根元(の名前)は委譲を受けるために存在しているので、CNAMEであってはならない。

もしURLなどで使いたいのであれば、Aレコードを定義する必要がある。

1.2. heroku での注意

https://devcenter.heroku.com/articles/avoiding-naked-domains-dns-arecords

Naked domains, also called bare or apex domains, are configured in DNS via A-records and 
have serious availability implications when used in highly available environments such as
massive on-premise datacenters, cloud infrastructure services, and platforms like Heroku.

For maximum scalability and resiliency applications should avoid naked domains and
instead rely solely on subdomain-based hostnames.

https://devcenter.heroku.com/articles/custom-domains

1.3. Google blog の制限

To simplify custom domain configuration on your blog, Blogger only accepts non-naked domains in our sign-up process.

1.4. zone_apex / CNAME 問題

http://blog.cloudflare.com/zone-apex-naked-domain-root-domain-cname-supp

One of the challenges of using a service like Amazon Web Services (AWS) Elastic Cloud (EC2) is you need to point your DNS to a CNAME.

The problem is the DNS RFC (RFC1033) requires the "zone apex" (sometimes called the "root domain" or "naked domain") to be an "A Record," not a CNAME.

This means that with most DNS providers you can setup a subdomain CNAME to point to EC2, but you cannot setup your root domain as a CNAME to point to EC2.

amazonなどの負荷バランスを使うのにはCNAME が使われるが、
 zone apex, bare, naked domain はCNAME RRは定義してはいけない。

http://serverfault.com/questions/305971/problems-with-bare-domains-and-dns-load-balancing

だが、naked domain 名をCNAMEにしているドメインもある。

2. www or naked

http://www.greenhills.co.uk/2011/06/12/www-or-bare-domain.html

Having the “www” has no technical drawbacks, but bare domains have two:
  the CNAME problem and the mail problem, which I would like to explore in some more detail.

http://david.latapie.name/blog/www-or-naked-domain-a-bottle-of-wine/

double-standard.

Consi­der tab­bed brow­sing. Only one page dis­played, tabs are hid­den. Open a new tab, the tab bar appears out of nowhere.

www.domain.fr makes sense for com­mo­ners.

text edi­tors with auto­link usually require a lea­ding www.

naked domain serves its own pur­pose: iden­ti­fying the domain itself.

Bot­tle of wine: "bot­tle" is the naked domain, "wine" is the sub­do­main.

a SSL cer­ti­fi­cate only applies to one sub­do­main.  So www-to-naked (or reverse) won’t work.

Google app engine won’t load balance on naked domain.

Google consi­ders a www site and a no-www site as dif­ferent sites with dupli­cate content.

2.1. unbounce

http://support.unbounce.com/entries/307687-how-can-i-use-a-naked-domain-a-domain-without-the-www-prefix-with-unbounce

2.2. www へ

Switching from a 'bare/naked' domain to 'www' http://www.speedilicious.com/support/onboarding/bare-domains/

2.3. JPでの調査

naked

76797

www

16998

total

93795

両方を設定:65

www がCNAME: 7628 (多段のCNAMEのものもあるが、RFCでは使わないように書かれている。)

 103 vdw5.mmjp.or.jp
 178 www.office.interq.or.jp
 189 ghs.google.com

amazon を指定しているのは23ドメインでした。

naked で指定されているAレコードの先: www.gmoserver.jp 800 ドメインあまり

-- ToshinoriMaeno 2012-06-03 23:49:56