[Users] DNS caching

Klaus Darilion klaus.mailinglists at pernau.at
Mon Feb 12 21:40:59 CET 2007


I wonder why you need DNs caching inside openser. Usually you will a
resolving name server near (in terms of network hops) to your SIP proxy.

E.g. I have a bind9 running on the same linux box as openser.  This name
server will be used by all processes running on this linux box
(/etc/resolv.conf points to 127.0.0.1 and to another name server in my
server farm).

Bind will cache all requests. A request for a domain which is cached in
bind will usually be <1ms and during waiting for the DNS response openser
wont cause CPU load - and probably the caching implementation in bind is a
good one.

Thus for me I do not see any reason for having the caching inside the SIP
proxy.

regards
klaus


On Mon, February 12, 2007 20:22, Christian Schlatter said:
> Now that OpenSER supports NAPTR/SRV lookups I'd like to add DNS caching
> to our SIP servers in order to decrease call setup delays and DNS server
> load introduced by DNS queries.
>
> I was wondering if others on this list have experience with running
> OpenSER together with a DNS cache solution like nscd or dnsmasq. Initial
> tests with nscd were not successful since somehow the OpenSER processes
> do not go through the ncsd caching, whereas e.g. ping does. I'm also not
> sure if ncsd or dnsmasq do support NAPTR and SRV type DNS queries.
>
> I'd be glad to hear any recommendations on this topic,
>
> Christian
>
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