SOA and NS are canonical records?

Christian Smith none at i.am.invalid
Thu May 6 03:01:40 UTC 2004


In article <c7b74h$unv$1 at sf1.isc.org>, "June" <nfbz2003 at yahoo.com> 
wrote:

> thanks for jumping in....
> 
> SOA and NS as canonical names are different from the other type of canonical
> name (A RR), for one thing, they can not be used as rdata, right?
> 
> In addition, these, and others like MX record, can also be understood as
> "alias", they redirect a particular type of record (MX, NS, SOA, etc) to the
> canonical names (an A record, as RDATA or MNAME in case of SOA).  My
> questions is why they are called canonical names, not alias, as they are not
> really that different from CNAME RRs.  I don't see them being referenced as
> canonical names in docs (I haven't read a lot reference), and I'd like to
> know these references if someone has seen them.  If there is a RFC defined
> them this way, I'd also like to know; or if people just refer to them this
> way, and have been doing this years, that's fine too, but I'd like to get
> some confirmations from the veterans here.

A CNAME record associates a "alias" with a canonical names.

As an example,

www.example.com.     43200   IN      CNAME   example.com.

In this case, "www.example.com" is an alias and "example.com" the 
canonical name.

Often people refer to "www.example.com" as being a CNAME, but this is 
incorrect.


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