While this mail has received no reactions on the mailing list, there is
some discussion happening on the GitHub repository.
The changes that are now scheduled for the new draft related to this
topic are:
* Define what intermediate records are.
* Update the TTL of the final address records to the minimum TTL of the
ANAME, intermediate records, and target records (add the initial ANAME
too in this step).
* Add some words about TTL stretching.
* Add an appendix section on ANAME substitution if done inside the name
server (for informational purposes).
Full diff related to this topic can be found here:
https://github.com/each/draft-aname/pull/61/files
Best regards,
Matthijs
On 5/2/19 11:21 AM, Matthijs Mekking wrote:
Hi,
Another issue that is still open related to ANAME is the TTL
considerations.
The current draft says that when updating sibling address records
with target address records to reduce the TTL to match the ANAME TTL if
it is greater.
I propose a change that others have expressed as well, that is the TTL
of the sibling address records should be set to the minimum of the
target address records and its intermediate records in case of CNAME
and/or ANAME chains.
The logic is that ANAME is likely to be a more static record, while its
target address records are expected to be more dynamic. Therefor it may
make sense to set different TTLs for the different RRsets, meaning we
should not try to match the ANAME TTL and the TTL of the address records.
This means that when implementing ANAME substitution at the primary,
this will likely stretch the end-to-end TTL (from the authoritative
servers for the target address records to end-user DNS caches) to near
twice the target address record original TTL.
The suggested change can be found here:
https://github.com/each/draft-aname/pull/61
I will leave this pull request open for a while to solicit feedback,
counter arguments, approvals, ...
Best regards,
Matthijs
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