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