RR and rrset

[Paul A Vixie]

> 	I'm embarrassed to admit it, but as long as I've been in this 
> business, I feel that I've never truly understood the difference 
> between RRs and RRsets -- until now.
> 
> 	Thanks, Paul!

Aw, shucks.  RFC 2136 7.12 says:

   7.12. Due to the TTL minimalization necessary when caching an RRset,
   it is recommended that all TTLs in an RRset be set to the same value.
   While the DNS Message Format permits variant TTLs to exist in the
   same RRset, and this variance can exist inside a zone, such variance
   will have counterintuitive results and its use is discouraged.

In fact, much of the debate which preceded the authoring and publication
of RFC 2136 was really just an institutional learning experience about the
difference between an RR and an RRset.  A thourough rereading of RFC 2136
gives any reader an absolutely firm basis for understanding this difference.