ttl for ns

[William Allen Simpson <wsimpson () greendragon com>]

During a complete renumbering, I'm trying to establish a standard for 
DNS records.  After all, every zone file is going to have to be touched, 
so we might as well update them at the same time.  Various techs have 
done odd things over the past decade.

Having no guidance so far from this group, despite the grumbling about 
times becoming shorter and lack of analysis, I thought "Well, vixie 
will know the best practice!"

I remain unenlightened.  Should it be 2 days?  Or 1 hour?  And why the 
inconsistent results?  Obsolete root glue records?

A simple dig yields:

;; ANSWER SECTION:
vix.com.                2D IN NS        ns-ext.vix.com.
vix.com.                2D IN NS        ns1.gnac.com.

;; AUTHORITY SECTION:
vix.com.                2D IN NS        ns1.gnac.com.
vix.com.                2D IN NS        ns-ext.vix.com.


But a dig directly to the ns1.gnac.com or ns-ext.vix.com server yields:

;; ANSWER SECTION:
vix.com.                1H IN NS        ns.lah1.vix.com.
vix.com.                1H IN NS        ns.sql1.vix.com.
vix.com.                1H IN NS        ns-ext.isc.org.
vix.com.                1H IN MX        10 sa.vix.com.
vix.com.                1H IN MX        20 fh.vix.com.
vix.com.                1H IN TXT       "$Id: vix.com,v 1.190 2004/08/12 19:06:05 vixie Exp $"
vix.com.                1H IN A         204.152.188.231
vix.com.                1H IN SOA       ns.lah1.vix.com. hostmaster.vix.com. (
                                        2004081201      ; serial
                                        1H              ; refresh
                                        30M             ; retry
                                        1W              ; expiry
                                        1H )            ; minimum


;; AUTHORITY SECTION:
vix.com.                1H IN NS        ns.lah1.vix.com.
vix.com.                1H IN NS        ns.sql1.vix.com.
vix.com.                1H IN NS        ns-ext.isc.org.

;; ADDITIONAL SECTION:
ns.lah1.vix.com.        1H IN A         204.152.188.234
ns.lah1.vix.com.        1H IN AAAA      2001:4f8:2::9
ns.sql1.vix.com.        1H IN A         204.152.184.135
ns.sql1.vix.com.        1H IN AAAA      2001:4f8:3::9
ns-ext.isc.org.         1H IN AAAA      2001:4f8:0:2::13
ns-ext.isc.org.         1H IN A         204.152.184.64
sa.vix.com.             1H IN A         204.152.187.1
sa.vix.com.             1H IN AAAA      2001:4f8:3:bb::1

-- 
William Allen Simpson
    Key fingerprint =  17 40 5E 67 15 6F 31 26  DD 0D B9 9B 6A 15 2C 32