The End-To-End Internet (was Re: Blocking MX query)

William Herrin bill at
Thu Sep 6 17:49:06 UTC 2012

On Thu, Sep 6, 2012 at 11:14 AM, Andrew Sullivan <asullivan at> wrote:
> RFC 2052, which defined SRV in an
> experiment, came out in 1996.  SRV was moved to the standards track in
> 2000.  I've never heard an argument why it won't work, and we know
> that SRV records are sometimes in use.  Why couldn't that mechanism be
> used more widely?

Hi Andrew,

Because the developer of the next killer app knows exactly squat about
the DNS and won't discover anything about the DNS that can't be had
via getaddrinfo() until long after its too late redefine the protocol
in terms of seeking SRV records. Leaving SRV out of getaddrinfo()
means that SRVs will be no more than lightly used for the duration of
the current networking API. The last iteration of the API survived
around 20 years of mainstream use so this one probably has another 15
to go.

Also there are efficiency issues associated with seeking SRVs first
and then addresses, the same kind of efficiency issues with reverse
lookups that lead high volume software like web servers to not do
reverse lookups. But those pale in comparison to the first problem.

Bill Herrin

William D. Herrin ................ herrin at  bill at
3005 Crane Dr. ...................... Web: <>
Falls Church, VA 22042-3004

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