Public DNS question - Trailing period

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Hello,
Hoping someone can describe the wherefors and whys regarding the MS DNS
practice of inserting a trailing period after every hostname record.

I first became aware of this issue when I set up using Windows as a Public
DNS server but didn't think much of it after that, considering it only a
peculiarilty.

Tom Shinder (esteemed ISA authority) posted today on a mail list list that
it's required, saying "... it's related to qualifying unqualifed names which
is related to how the client resolver works."

In the software world, I have sometimes seen how a trailing character can be
important because appended strings don't always lead with an appropriate
character, breaking the string's delimitation.

Example
Querying for "Hostname" in "MyDomain.com"
If a query for "Hostname" does not automatically insert a trailing period,
the query is for "HostnameMyDomain.com" instead of "Hostname.MyDomain.com"

So, first question:
Is the reasoning behind a DNS hostname trailing period the same and if so
what situations would this be important?

Second question:
Tom's comment was actually a response in a thread where it was asked why
NSLOOKUP querying a remote, non-cached domain/hostname times out. Others
including myself tested and found that the trailing period did not make a
difference although the query might have to be repeated after a few seconds.
Should a trailing period make a difference here? Obviously if the trailing
period is <only> for the delimiter reason I mentioned above, then I don't see
how it should be important for a simple query, but am looking for a more
detailed explanation.

Thx,
--
Tony Su
www.su-networking.com
ISA
SBS
Enterprise Mobile Solutions Architect
.

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