[Serusers] Intermittent Audio

[pat newham]

Hi Greger,

The system is currently being tested by someone else
but I believe they are behind a Linksys VPN router.
Are you suggesting it could simply be the settings in
this? 
I "think" I understand the nat issues associated with
sip and sdp fairly ok so would I be correct in saying
that if my two clients are behind nat(the same nat)on
the same subnet the rtpproxy should be invoked? This
would be my understanding of the situation but then I
saw a recent email (see message header below)which
suggests an external script should be used.

Re: FW: [Serusers] calls between UA´s b ehind same NAT
us ing nathelper/rtpproxy

Also what confuses me is that the scenario works
sometimes and yet other times it doesnt. I will
attempt to get a full message dump (of both the
working and non working scenario)from the tester if
that will help.

Kindest Regards,
Pat.

--- "Greger V. Teigre" <greger at teigre.com> wrote:
> Pat,
> You haven't said anything of the type of NAT you are
> behind. To me it sounds 
> like an ALG (Application layer gateway) problem. Try
> to turn of the SIP ALG 
> in your router.  If not, please post a full SIP
> message exchange.  You need 
> to find out if they communicate through the NAT
> (hairpin media) or directly. 
> That depends on the SDP payload in the INVITE and OK
> messages.
>     The new Getting Started document on
> http://onsip.org/ (you need to 
> register) has a thorough review of NAT issues and
> rewriting. Recommend!  (I 
> wrote it ;-) )
> g-)
> 
> pat newham wrote:
> > Following on from my below email, I can now
> definately
> > say the problem is not nat pings. Just to recap I
> am
> > experiencing intermittent audio. It works when the
> > phones have very recently registered, then
> sometimes
> > theres one way audio and then sometimes no audio.
> Does
> > anyone have any ideas what the problem could be or
> > where I could begin to troubleshoot this?
> >
> > Hi,
> >
> > I have a strange problem. I have two grandstream
> > budgetone clients on the same subnet behind nat
> > registering with ser on a public address.
> Obviously
> > their public addresses would be the same but they
> > listen on different ports. When they initially
> > register, I can the call,audio is transmitted and
> > everything is successful.
> >
> > However sometimes theres only one way audio, other
> > times theres no audio and then other times it
> > works....I am guessing that this is because the
> nat
> > router is forgetting the nat mapping so after a
> while
> > when the nat mapping is "forgotten" and a packet
> > arrives destined for a client, the router drops
> it....
> >
> > Could someone verify this for me??...Am I on the
> right
> > track?? I have the following settings in ser.cfg
> which
> > I thought would keep the nat settings alive.
> >
> > modparam("registrar", "nat_flag", 6)
> > modparam("nathelper", "natping_interval", 30) #
> Ping
> > interval 30 s
> > modparam("nathelper", "ping_nated_only", 1)   #
> Ping
> > only clients behind NAT
> >
> > I also increased the nat keep alives "pings" sent
> in
> > the configuration settings of the grandstream
> > phone....Any further ideas??
> >
> > Regards,
> > Pat.
> >
> > Send instant messages to your online friends
> > http://uk.messenger.yahoo.com
> >
> > _______________________________________________
> > Serusers mailing list
> > serusers at lists.iptel.org
> > http://lists.iptel.org/mailman/listinfo/serusers 
> 
> 

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