Re: [DNSOP] BCP on rrset ordering for round-robin? Also head's up on bind 9.12 bug (sorting rrsets by default)

[Shumon Huque <[e-mail]>]

On Fri, Jun 15, 2018 at 6:40 PM Mark Andrews <[e-mail]> wrote:

> What we should be asking is why a service that needs multiple machines
> isn’t using SRV. It has randomisation between servers explicitly defined
> along with proportional load balancing.
>

That would be nice, but sadly major applications like the web, have (in my
assessment) never seriously shown any interest in using SRV records. To
quote some of the discussion of HTTP2 on this subject:

from https://lists.w3.org/Archives/Public/ietf-http-wg/2015AprJun/0674.html:

--- excerpt

"We discussed this, but decided not to support SRV in HTTP/2 - mostly
because HTTP/2 needs to be backwards-compatible with the existing Web,
which doesn't use SRV. In discussion, it also became pretty clear that if
we were to use an additional record type for HTTP, SRV may not suit,
because we need to do things like protocol version negotiation.

There were also concerns about latency and interoperability (especially
considering how many DNS requests a page load can make, and the unfortunate
limitations of some DNS gateways/proxies)."

--- end excerpt

The latter point about additional latency, due to the need for additional
follow-on queries to resolve the address records for the SRV targets (if
the resolver hasn't provided them), has been a pretty potent blocker for
SRV adoption in the web.

Also, in my experience, many implementations of client applications that do
employ SRV don't even bother to implement the load balancing aspect, just
the priority aspect. This was particularly true in Kerberos from my
recollection.


> It also addresses CNAME at the apex which quite frankly is only used to
> find the name of the HTTP server for the zone which SRV  is quite capable
> of doing.
>

Yup ..

Shumon.