[dns-operations] Prime TTL values for TLD and root server delegations.

[Robert Edmonds]

David Dagon wrote:
> There might be unintended costs of random prime TTLs.  If an authority
> did vary its TTLs (e.g., providing 86413, 86423, 86441, 86453, 86461,
> 86467, 86477, 86491, 86501, 86509, 86531, etc., randomly instead of
> 86400) it might trip up primitive DNS monitoring heuristics (e.g.,
> those looking for flux-style networks).  Research projects that store
> unique records, and use the TTLs for uniqueness, would also see an
> explosion in storage.

note that the TTL is the _maximum_ length of time an RRset may validly
be cached for.  if there do happen to be measurable operational
advantages to prime TTLs, it would be much easier to simply have the
cache lower the TTL of a cached RRset to a nearby prime.

-- 
Robert Edmonds
edmonds at isc.org