Re: [cobalt-users] Adjusting TTL for domain change

[Jeff Lasman <jblists@xxxxxxxxxxxxx>]

SM wrote:

> Before getting into TTL, let's see why do we want DNS to be cached.  First
> of all, it makes name lookups faster.

That was the general idea when the DNS was first invented.  But now,
especially for us hosting our own DNS on the same machine as the site it
really makes no difference at all.

> This means that it takes less time
> for the user's box to get your IP address and establish a connection to
> your site.

The first DNS packet is generally under 50 bytes.  The return is
generally under 250.  So do two small packets make that much of a
difference considering all the data transit to come?  Not much really.

> DNS caching also reduces the load on the user's DNS server and
> your DNS server.

Agreed.

> A higher TTL offers more stability.  If your web server
> is running and your DNS servers are not responding, the user can still
> reach your website if your DNS records are cache-friendly.

For most of us if our DNS server is done, so are our websites.  However
the difference in the error message is important; if DNS is cached
elsewhere, or you've got a good secondary elsewhere, then the user will
read that the site is temporarily unreachable.  If your DNS wasn't
cached anywhere, the user will read that the domain doesn't exist.  Big
difference.

Jeff
-- 
Jeff Lasman <jblists@xxxxxxxxxxxxx>
Linux and Cobalt/Sun/RaQ Consulting
nobaloney.net
P. O. Box 52672, Riverside, CA  92517
voice: (909) 787-8589  *  fax: (909) 782-0205