On Nov 30, 2009, at 9:43 PM, Mark Andrews wrote:
> In message <402431.44413...@web112611.mail.gq1.yahoo.com>, gmspro writes:
>> What's the main difference between zone and domain?
>> It's confusing to me,I'm searching though,i got once,"zone is a portion of do
>> main".
>>
>> Can someone give example to clear things up?
>
> example.net. SOA ns.example.net. hostmaster.example.net. (
> 1 3600 1200 360 1200 )
> example.net. NS ns.example.net.
> ns.example.net. A 1.2.3.4
> www.example.net. A 1.2.3.5
>
> All the above form a zone which would be called example.net.
>
> example.net, ns.example.net and www.example.net are individual domains
> within the zone.
While that's true assuming there are no other records in the zone, consider
what happens if you add this record:
sub.example.net. NS ns.sub.example.net.
Now the "example.net" domain extends below the bottom of the zone.
Ahem... (puts on lecturer robes...)
The domain name system is structured as an inverted tree, with a root at the
top and other nodes below. Each node has exactly one parent, except for the
root node, which has none.
A "label" is the short name given to a particular node.
A "domain name" is the full name of a node. It is equal to the name of the node
and all of its ancestors, in order from the node itself to the root, left to
right, separated by dots.
A "domain" is a subtree of the namespace - a given node and any and all
descendants. It is named for the node at the top (the "apex"). The entire
namespace is a domain named "." (which is how we write the name of the root
node). Every domain name corresponds to a domain, although possibly a domain
containing just a single node.
A domain can be divided administratively into units called "zones". A zone,
like a domain, has a single node at its apex. The difference is, there can be a
cut in the namespace separating a child zone from its parent. That is, a zone
is equal to a domain of the same name (i.e. having the same apex) minus any
child zones.
For example, consider the following well-known domain names:
"." (the root)
com.
example.com.
www.example.com.
Each of these domain names except the last is the apex of a zone. All of them
are the apexes of domains. The node named "www.example.com." is a member of
each of these domains, but only one of these zones (example.com.). That's
because the zone "example.com." is delegated (separated by an administrative
cut) from its parent, "com.", although it is still a member of the "com."
domain.
Is it clear yet?
Chris Buxton
Men & Mice
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