On Thu Jul 21 23:15:59 2011, Bruce Atherton wrote:
So if you have no control over the DNS, it is not a problem. The
host will be resolved exactly the same way as it is now, using a
hosts file or A record or whatever. The only change is that the
client is required to try to use the more advanced mechanism if it
is available.
Right.
I admit that I find it a little troubling to use MUST for the
client to follow this procedure as there is a burden on
implementers to understand how to code this since it isn't done by
default in the standard libraries the way that ordinary name
resolution is. Making it the recognized best practice with a SHOULD
would be preferable all else being equal.
SRV lookup is pretty commonplace now in libraries. XMPP and SIP
clients have no difficulty finding this functionality in a wide
variety of environments. For the web, where there are substantially
fewer web browsers than there are XMPP clients, I don't think this
would pose any kind of problem.
It can be argued that not using a MUST may well open up
interoperability problems because some Websockets clients contact
the wrong host. However, keep in mind that in the older SIP RFC2543
it provided two resolution mechanisms. It specified that clients
SHOULD look up address records, but MAY use the DNS SRV mechanism.
SIP survived that without too much of a hassle. And specifying that
Websockets clients SHOULD use DNS SRV, but MAY use address records
alone looks like an improvement.
SIP survived because it was very small. I don't see WS making a
transition, in the same way that repeated attempts have failed to
move HTTP to SRV.
Dave.
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Dave Cridland - mailto:dave@xxxxxxxxxxxx - xmpp:dwd@xxxxxxxxxxxxxxxxx
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