cet1 at cam.ac.uk
Wed Feb 11 15:37:32 UTC 2009
On Feb 11 2009, Johnny wrote:
>_sip._udp.as.host.com as1.host.com 0 1 5060
>_sip._udp.as.host.com as2.host.com 0 0 5060
That's the wrong syntax. I'll assume you mean
_sip._udp.as.host.com. SRV 0 1 5060 as1.host.com.
_sip._udp.as.host.com. SRV 0 0 5060 as2.host.com.
>Since "as1" has a higher weight, it will always be picked first by the
>SRV aware client?
Not because it has a higher weight, but because it has an *infinitely*
>I want the devices to ALWAYS go to "as1" and only go to "as2" if "as1"
>is not available.
>Do the above lines accomplish that?
Yes, but in a perverse way, IMNSHO. It's more natural to use priorities
rather than weights, if that's what you want:
_sip._udp.as.host.com. SRV 0 100 5060 as1.host.com.
_sip._udp.as.host.com. SRV 1 100 5060 as2.host.com.
That defines a strict ordering. If you had
_sip._udp.as.host.com. SRV 0 2 5060 as1.host.com.
_sip._udp.as.host.com. SRV 0 1 5060 as2.host.com.
then a client is meant to try as1 2/3 of the time, and as2 1/3 of
the time. The intended consequences of using a zero weight value
are spelled out in detail in RFC 2782, but there is no need to
rely on them.
Email: cet1 at cam.ac.uk
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