[Date Prev][Date Next] [Thread Prev][Thread Next] [Date Index] [Thread Index]

Re: Pick a name, any name...



"John H. Robinson, IV" <jhriv@ucsd.edu> writes:

> because with a A record one lookup -> IP address(es)
> with a CNAME one lookup -> another lookup -> IP address(es)
> 
> CNAME cause you to at least DOUBLE the DNS lookups, DOUBLING the
> potential timeouts, DOUBLING dns load
> 
> can you do it? certainly. should you be aware of the effects WHEN you do
> it? yes. you may break the rules only after you understand the rules.

There is no rule that CNAME records are only for non-local pointers.
Yes, a CNAME does additional lookups.  DNS traffic to leaf servers
is an insignificant piece of total traffic.

> > DNS entries are cached and don't cause that much traffic.
> 
> the second and subsequent times, yes. not the first time.

A local CNAME doesn't do double traffic.  Suppose I have a CNAME for
www.bar.baz -> fletch.bar.baz.

Looking up an A record in this domain will require:

query for baz.
query for bar.baz.
query for fletch.bar.baz.

Looking up the CNAME is only 33% more traffic, not "at least double":

query for baz.
query for bar.baz.
query for www.bar.baz.
query for fletch.bar.baz.



Reply to: