cname quick question

[Erik Aronesty]

JIM>Please *read* the extract from RFC1034 above. Now *think* about what
JIM>it says and what that means. Pay particular attention to the last
JIM>sentence. Hint: suppose clueless.example.com was a CNAME pointing at
JIM>moron.example.net. That CNAME is cached by some name server. It can
JIM>safely use that cached CNAME without having to query the example.com
JIM>name servers to check that no other record types exist for
JIM>clueless.example.com.

1- Suppose clueless.example.com was at the zone top with a "@ IN CNAME moron.example.net."

2- The CNAME can still get cached by a name server.  The CNAME can still be
   safely used from the cache -and no other record types ever have to be queried -
   since the SOA and NS record types are transmitted in the authority section.

4- You example just shows that you arent' paying attention.

			- Erik


--- thread below ---

-----Original Message-----
From:	Jim Reid [SMTP:jim at rfc1035.com]
Sent:	Thursday, March 01, 2001 5:16 AM
To:	Erik Aronesty
Cc:	bind-users at isc.org
Subject:	Re: cname quick question

>>>>> "Erik" == Erik Aronesty <erik at primedata.org> writes:

    >> If a CNAME RR is present at a node, no other data should be
    >> present; this ensures that the data for a canonical name and
    >> its aliases cannot be different.  This rule also insures that a
    >> cached CNAME can be used without checking with an authoritative
    >> server for other RR types.

    Erik> Exactly.  How does having a CNAME at the zone-top cause this
    Erik> to be an error?  For that mater how does having an SOA
    Erik> record fail to allow cached CNAMES to be used without
    Erik> checking an authoritative server for other RR types?  It
    Erik> doesn't.  Because the SOA record is used for zone transfers
    Erik> and cache/timing information itself.  The RFC neglected to
    Erik> mention that.  That's all.

JIM>Like Tal Dayan, you are being obtuse or deliberately provocative.
JIM>Please *read* the extract from RFC1034 above. Now *think* about what
JIM>it says and what that means. Pay particular attention to the last
JIM>sentence. Hint: suppose clueless.example.com was a CNAME pointing at
JIM>moron.example.net. That CNAME is cached by some name server. It can
JIM>safely use that cached CNAME without having to query the example.com
JIM>name servers to check that no other record types exist for
JIM>clueless.example.com.

1- Suppose clueless.example.com was at the zone top.

2- The CNAME can still get cached by a name server.  The CNAME can still be
   safely used from the cache -and no other record types ever have to be queried -
   since the SOA and NS record types are transmitted in the authority section.

4- You example just shows that you arent' paying attention.

			- Erik