[dns-wg] lameness and unreachability

Ed Lewis wrote:

> >W	SOA 'minimum' less than 3 hours
> >W	SOA 'refresh' at least 6 hours
> >W	SOA 'retry' at least 1 hour
> 
> I would think that these are policy dependent - sometimes shortened 
> numbers are a good thing - if you are willing to pay the performance 
> price.

"you" is us in certain cases. As discussed in RIPE 203 the refresh and retry
values affect the zone server operators. It's useful to check relative
consistency, i.e. retry<refresh, refresh + retry < expire etc, but the
absolute numbers are probably less important (certain implementation
specific boundaries nonwithstanding).
The "minimum" value as well as the TTL values affect the overall DNS cache
performance, so everybody pays the price. A warning is appropriate for certain
thresholds, since zone maintainers dealing with exceptional cases should be
able to interpret that warning with a grain of salt.

> >W	serial number of the form YYYYMMDDnn (RFC1912)

I did not yet see the original message, but I guess there's a "not" missing
here.

> With the advent of dynamic update, the last is no longer recommended.

Well, I'd rephrase that to "there are more cases where this recommendation
is inappropriate". Still the vast majority of zones is small and stable,
so it's unlikely Dynamic Update will be used there. However, that
recommendation has another drawback. I've seen many cases where after
initial setup (probably done by an external consultant) subsequent
SOA serial changes were left to the GUI interface/server maintenance tool,
which just increases the value by '1'. That means you see the common format,
you think it encodes the date of the last change and you're fooled.

-Peter