On 1/4/02 11:53 PM, [EMAIL PROTECTED] at
[EMAIL PROTECTED] wrote:
> Theoretically true.
>
> In real life, don't expect it to actually happen. AOL is notoriously
> slow about updating their DNS servers. In my neck of the woods, the
> University of Texas is also. I always assume that it'll be at least
> a week - and if I have the ability, a month - before everyone is
> getting the correct info.
Other than on the defined authoratative DNS servers, there is nothing to
update. All other servers, once they've had to retrieve the data, cache it
for TTL seconds. After that, they're supposed to discard the data and
reacquire it from an authoratative server if it's requested again.
So the only way a server could be "notoriously slow about updating their DNS
servers" is if they're not honoring the TTL and caching it longer than that
which would make their DNS server non-compliant with the appropriate RFCs.
However, when you cut TTLs, make sure you also cut the refresh interval of
any secondary DNS servers for your zone or can arrange to force a reload of
your secondaries. It does no good to cut TTL to 5 minutes if the secondary
is only checking for zone changes every 3 hours as your secondaries will
still be serving the old data for up to 3 hours (or longer if the primary
server is unreachable) ("refresh" defines the interval the secondary checks
with the primary for zone changes, if it can't reach the primary, it then
rechecks in "retry" seconds but will continue to serve the zone data it has
until the primary cannot be reached for "expire" seconds - typical values
are 3 hours for refresh, 1 hour for retry, and 1 week for expire).
...
>> Doesn't one usually decrease the TTL for the DNS entry before it is
>> changed on the DNS server? That would allow the rest of the world a
>> pretty quick change to the new records.
-- Larry Stone
[EMAIL PROTECTED]
http://www.stonejongleux.com/
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