On Wed, 2010-04-28 at 15:05 -0400, Worley, Dale R (Dale) wrote:
> Looking at a problem a user had, I see that the DNS zone file that we
> automatically generate has an "expire" time that is the same as the "refresh"
> time. In the user's example:
>
> IN .
> $TTL 1800 ; 30 minutes
> mysipdomain.it IN SOA ns1.mysipdomain.it. root.mysipdomain.it. (
> 2010042303 ; serial
> 1800 ; refresh (30 minutes)
> 1800 ; retry (30 minutes)
> 1800 ; expire (30 minutes)
> 1800 ; minimum (30 minutes)
> )
>
> This means that if a DNS secondary cannot contact the DNS primary every 30
> minutes, it will give up on providing answers for the domain.
>
> Looking at RFC 1912, Common DNS Operational and Configuration Errors, I see
> this advice:
>
> Expire: How long a secondary will still treat its copy of the zone
> data as valid if it can't contact the primary. This value
> should be greater than how long a major outage would typically
> last, and must be greater than the minimum and retry
> intervals, to avoid having a secondary expire the data before
> it gets a chance to get a new copy. After a zone is expired a
> secondary will still continue to try to contact the primary,
> but it will no longer provide nameservice for the zone. 2-4
> weeks are suggested values.
>
> This suggests the generated expire value should be at least 2 weeks.
>
> The template for the DNS zone file appears to be
> sipXcommserverLib/bin/sipx-dns.in. I think we should change the template for
> the SOA record to:
>
> generate_zone_header () {
> ZoneSerialNumber=`date +%Y%m%d${SerialNumber}`
> cat <<EOF
> \$TTL 1800
> @ IN SOA ns1.${SipDomain}. root.${SipDomain}. (
> ${ZoneSerialNumber} ; serial#
> 1800 ; refresh, seconds
> 1800 ; retry, seconds
> 1209600 ; expire, seconds
> 1800 ) ; minimum TTL, seconds
> EOF
> }
>
> (1209600 seconds = 2 weeks)
>
> Thoughts?
+1
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