On Jun 16 2010, Niobos wrote:
Hi,
I'm a bit confused on how exactly to implement the SRV records.
At this moment, it's more an exercise for me, since client software
doesn't use them (yet).
I have a CALDAV server running on a vhost (apache config). Currently,
DNS looks like this:
caldav CNAME server
server A 1.2.3.4
AAAA dead:beef:cafe::1
So in fact, I'm already abusing CNAME to map a service to a host. This
is convenient, since the IP is only specified once. (So if it changes,
there is no risk of overlooking an entry)
If that's "abuse", we are all guilty of it!
The trouble starts when adding SRV records. Spontaneously, I'd add
_caldav._tcp SRV 10 10 80 caldav
However, RFC2782 explicitly states that: the name MUST NOT be an alias
Which would require me to change DNS to look like:
caldav A 1.2.3.4
caldav AAAA dead:beef:cafe::1
server A 1.2.3.4
server AAAA dead:beef:cafe::1
_caldav._tcp SRV 10 10 80 caldav
In this configuration, the server's IP is present multiple times, which
will lead to mistakes in the future. I can't let the SRV-record point
directly to "server" either, since the vhost-configuration needs the
correct Host:-HTTP header.
Or am I missing something?
You are mixing up protocol names and service names. If CalDAV is
standardised to used the "caldav" protocol name in SRV records,
and you want to use the service name caldev.example.com, you would
put
_caldev._tcp.caldev SRV 10 10 80 server
in your (example.com) zone file. The first component is the protocol
specifier, the third is the (initial component of) the service name.
And such a SRV record can co-exist with your existing CNAME for
caldev.example.com, which is just as well while the applications
take umpty-ump years to make the transition...
--
Chris Thompson
Email: c...@cam.ac.uk
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