subdomain alias or subdomain forward?

//=== "subdomain forward" is different from "subdomain alias"
subdomain forward is done by 'A record'
subdomain alias is done by 'CNAME record'

* subdomain alias 會將輸入的域名保留在瀏覽器的網址列
[例]
it.3hd.me 其實是指向 3hitek.blogspot.com
在網址列仍顯示 it.3hd.me

* 典型的subdomain forward (without masking) 網址列則會顯示域名所轉指的url,
[例]  book.3hd.me --> 3hbook.blogspot.com
網址列顯示 3hbook.blogspot.com

* masked subdomain forward (subdomain with masking) 則可達到類似alias的效果, 與CName alias 不同的是即使點選連結到外部的網頁
masked subdomain 的框架(frame/mask) 會一直籠罩著之後的網頁,
網址列始終顯示原來輸入的域名值, 這使得許多搜尋引擎會特意過濾掉
masked subdomain, 因而影響SEO (seach engine optimization).


[例]  tour.3hd.me  --> 3htour.blogspot.com
網址列顯示 tour.3hd.me , 即使點選外部連結, 網址列依然顯示 tour.3hd.me

""" ...
The main disadvantage of this type of forwarding is that is uses Frames.
...
Many search engines, such as Google, ignore framed content, and so your site will not be found easily ...
..."""


* subdomain forward 所增加的 A records
book    A     50.63.202.15  
tour      A    184.168.221.30


* subdomain alias 的設定比較麻煩, cname record並非直接指向目標網址,
而是要知道目標網址的域名伺服器(domain name server) ,
如果要指向既有的blogger(blogspot.com) 或是 google site, 則cname record 的 值要設為 ghs.google.com

[例]
it                  CNAME     ghs.google.com
yyyxxxzzz   CNAME     afjklgjkljajdkturjkj5.dv.googlehosted.com

除了正常的別名設定之外 it --> ghs.google.com ,
google 還會要求增加另一個隨機產生的 cname record 以驗證域名的所有權,
yyyxxxzzz   -->    afjklgjkljajdkturjkj5.dv.googlehosted.com


"""...
For security reasons, your domain must be verified with Google. See the below section, 'Domain is not verified' error ...

..."""



[ref]
http://wiki.gandi.net/en/domains/management/domain-as-website/forwarding

https://support.godaddy.com/help/article/5112/mapping-your-domain-name-to-work-with-blogger
https://support.godaddy.com/help/article/422/manually-forwarding-or-masking-your-domain-name


https://support.google.com/blogger/troubleshooter/1233381
https://support.google.com/sites/answer/99448


//=== https://www.linode.com/docs/networking/dns/introduction-to-dns-records
""" ...
 a CNAME record does not function the same way as a URL redirect.
... """


//=== use subdomain alias binding to backup/spread/aggregate your blogs
運用subdomain alias/forward 將散落各處的部落格集中在自己的網域,
方便存取/管理, 也達到縮址(縮短網址)的效果.


//=== 將自己的 subdomain 指向 github

http://www.openfoundry.org/index.php?option=com_content&task=view&id=9307&Itemid=4;isletter=1

""" ...

用 CNAME 的方式將一組子網域名稱指向你的 Github Pages
...

•將受惠於 Github Pages 站台的 CDN 效益。

•Github Pages 伺服器換 IP 的時候你不必跟著換否則其他人就連不上去。

•網頁載入的速度較快。

... """

//=== https://support.google.com/blogger/troubleshooter/1233381
""" ...
1.Go to your blog and click on Basics under the Settings tab. In the "Publishing" section, click the link to add a custom domain.

Add a custom domain
... """

//=== https://support.godaddy.com/help/article/5112/mapping-your-domain-name-to-work-with-blogger
To Edit Your CNAME Record

"...
1. Log in to your Account Manager.
Next to Domains, click Launch.
2. Click the domain you want to use, and then select the 'DNS Zone File' tab.
3. Click Add Record.
4. Select CNAME (Alias)for the Record type.
....

Click Save, and then click Save Changes.

... """


//===
domain : 網域
domain name : 域名
subdomain: 子網域

registrar : 域名註冊商, 網域代理商,
例如 godaddy.com, name.com, namecheap.com ...