[Asterisk-Users] Why is the internet connection important to LAN and PSTN calls?

[Andre Ruiz]

Would that caching dns daemon be "nscd"? (included in every distro).

I had some problem with it in the past and don´t like it, but it´s
major function is to turn a workstation capable of self-caching DNS
and NIS queries.

andre

On 4/11/06, Joseph Tanner <joseph at thetechguide.com> wrote:
> I've had this problem too.  It would get so bad, that it wouldn't even
> answer incoming calls, and if I tried to dial out via pstn, I would
> have hung up before it got around to dialing (which it would
> eventually do, unfortunately).
>
> A short-short term solution was to install bind, and use it as your
> primary nameserver.  Hopefully it'll cache dns queries long enough to
> survive an outage.
>
> A slightly better (in my opinion) solution would be to code a pure
> caching dns server, whose sole purpose is to look up specific domains
> and resolve them to their ip address.  It'll record the result, and
> will check every so often (once a minute, hour, day, whatever) and
> update its results.  If it cannot get an answer, it keeps using the
> last known ip address.  If anyone knows of a really bare-bones,
> standards-breaking dns server that would say, check a flat file
> database each time a request is made, we could run a daemon that would
> check the domains we need to resolve; if no answer is received, we
> just skip that line.  That way the daemon will be sitting there
> waiting for a dns answer, and not asterisk.
>
> The best solution would be to "fix" asterisk (I say "fix", as I'm sure
> many will say it's not broken, that's fine).  If your internet
> connection fails, there's no reason to have internal calls and calls
> in and out of your pstn lines failing too.  Personally, I have a
> toll-free line that runs over voip, and if it can't reach my server,
> it'll fall back and dial a landline I have.  In this case though, if
> my internet connection is down for an extended period of time, even
> those calls won't make it through.
>
> Joseph Tanner
>
> On 4/11/06, picciuX <matteo at picciux.it> wrote:
> >
> > because, a this time, the sip stack doesn't have asynchronous DNS... so ALL
> > the sip code is stucked waiting timeouts for DNS queries (that are long
> > timeouts).
> > When you try to dial a LAN device, the sip code is trying to resolve your
> > voISP service providers' addresses.
> > We workaround this putting all external sip peers in a separate file, say
> > "sip_peers.conf", included in sip.conf with "#include filename".
> > Then, a daemon on the box try to resolve well-known addresses on well-known
> > DNS servers on the net, every 5 minutes. If the demon fails ALL the
> > well-known DNS queries, it assumes no internet connection is available: then
> > it renames sip_peers.conf, and ask asterisk a "sip reload". So all external
> > sip references are out, and sip still continue working for internal phones.
> > Needless to say, when connection come up again, the daemon do the opposite
> > thing.
> >
> > hope this helps
> >
> >
> > 2006/4/11, Brent Torrenga <lists at torrenga.com>:
> > > Out internet connection was out this morning. It seems that the SIP
> > > extensions on our LAN were affected. Behavior like:
> > >
> > > Call comes in over POTS to a TDM400P, there is a delay then before the
> > Cisco
> > > 79[46]0's start to ring.
> > > If we were lucky enough to get a call through, then we could not transfer
> > > the call, or place the call on hold, or park the call.
> > > Outbound calls seemed to have a delay between the time they were dialed at
> > > the SIP phone and when they were connected.
> > >
> > > I know this has been brought up before, in fact there is a bit of a
> > > discussion going on now about DNS SRV (in sip.conf, set srvlookup=no, or
> > put
> > > all the phone ip's on /etc/hosts). But what is really causing the issue
> > > here? Yes, it is DNS, or something related to DNS, but why does that have
> > > anything to do with * trying to make a phone ring on the LAN?
> > >
> > > I would think that by using qualify=yes for any outbound voip trunks we
> > > avoid an issue of trying to call out is the net is down, but why are any
> > > operations on the LAN affected?
> > >
> > >
> > > Sincerely,
> > >
> > > Brent A. Torrenga
> > > brent.torrenga at torrenga.com
> > >
> > > Torrenga Engineering, Inc.
> > > 907 Ridge Road
> > > Munster, Indiana 46321-1771
> > >
> > > +1 219 836 8918 x325 Voice
> > > +1 219 836 1138 Facsimile
> > > www.torrenga.com
> > >
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--
Andre Ruiz  <andre.ruiz at gmail.com>
Curitiba, PR, Brasil