How to make SRV records work with caching resolvers?

[Mark Andrews]

The client is supposed to lookup missing address records. Complain to the supplier of the phone that they have a defective product. 

-- 
Mark Andrews

> On 13 Jul 2022, at 21:18, Peter <pmc at citylink.dinoex.sub.org> wrote:
> 
> 
> My Telco has removed the A record for their VoIP server, and now has
> only SRV data there - which seems not to work properly.
> 
> The SRV data contains various services (SIP via UDP, TCP, secure
> TCP, whatever), and these get individual expiry counters in the
> caching resolver.
> So when a telephone sends a query, the caching resolver will provide
> that data in the "Additional section" - but only those records that
> have not yet expired. 
> 
> If the configured service (the one the telephone should use) is no
> longer contained in the answer (but others are still present), the
> telephone goes offline until all the records have expired and a new
> authoritative query is made.
> 
> The Telco is of no help - they just want to sell their own equipment.
> 
> The telphones (Alcatel) are the usual linux plastic box, and I cannot
> easily hack these. It probably does not behave fully correct, but
> also not fully wrong.
> 
> In BIND/named I didn't find an easy approach to fix the issue - it
> doesn't look like it is supposed to be fixed there. And before I go
> for the more difficult approaches, I would like to ask how this
> is actually supposed to work, at all.
> 
> 
> -- PMc
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