[Freeswitch-users] Audio quesion

Steven Ayre steveayre at gmail.com
Fri Aug 13 12:48:59 PDT 2010


What is FreeSWITCH running on? Linux?

Iptables has a module which recognises RTP packets attached to a SIP session
and will mark them as RELATED. If his firewall is state based then it may be
automatically opening the RTP ports for the call even if they are normally
blocked.

There will be two separate connections for a call:
1. Signalling
2. Media

Signalling will be between port 5080 and a random port on the client. It can
be UDP or TCP (normally UDP). Media is a separate protocol (RDP), it will
always be a separate connection never to port 5080. There's just no way for
it to piggyback on the SIP.

SIP contains SDP, this contains the information on where to send media to.
On a call to the server, the INVITE will contain SDP from the client which
will contain the IP and port on the client which will receive media (one end
of the connection). When the server starts sending media it will send a SIP
180/183/200 with SDP. This will contain the IP and port at the server end
for the client to send media to. If you collect a packet trace of the call,
you will be able to see the IPs and ports that media will be using. Or by
capturing the RTP packets to see where they're going from/to.

Media can either go via the server (which would require the port to be open,
or a state based firewall) or bypass it (bypass media mode, where the client
IPs are in the SDP not the server so the connection is opened directly
between the clients, therefore no open port is required on the server).

-Steve



On 13 August 2010 20:12, Marshall Harrison <marshall at gotspeech.net> wrote:

> I know that.
>
> I'm trying to determine how a client's serve which he claims only has port
> 5080 open is working. If what he is saying is true then I don't see how the
> calls are working. I can't get into the system so I am having to debug
> based
> on what he is telling me.
>
> FreeSWITCH is front ending a Microsoft Speech Server and is a trusted SIP
> Peer. When a call comes in SesWorker  opens a port for RTP with the SIP
> Peer
> that can be anything from 1024 - 65535.  That RTP channel is between
> FreeSWITCH and Speech Server.
>
> So does FS then open that same port with the originator of the call or does
> it negotiate a different port?
>
> Marshall Harrison
> marshall at gotspeech.net |    904.342.6205
>
> -----Original Message-----
> From: freeswitch-users-bounces at lists.freeswitch.org
> [mailto:freeswitch-users-bounces at lists.freeswitch.org] On Behalf Of Sergey
> Okhapkin
> Sent: Friday, August 13, 2010 2:45 PM
> To: FreeSWITCH Users Help
> Subject: Re: [Freeswitch-users] Audio quesion
>
> You need to learn the basics of SIP. SIP does signaling only, audio
> parameters are passed in SDP.
>
> On Friday 13 August 2010, Marshall Harrison wrote:
> > I have FreeSWITCH setup to answer calls on port 5080.
> >
> >
> >
> > If I have 2 simultaneous calls are both going over port 5080 or is
> > that  just listening port and the calls get routed to a different port?
> >
> >
> >
> > What port is the audio going over? 5080? A different port for each call?
> >
> >
> >
> > Thanks.
> >
> >
> >
> > Marshall Harrison,
> > <https://mvp.support.microsoft.com/default.aspx/profile/marshall.harri
> > son>
> > MVP Microsoft Communications Server
> > GotSpeech Consulting LLC
> >
> >  <http://gotspeech.net/> www.GotSpeech.Net |  <http://gotuc.net/>
> > www.GotUC.Net
> >
> > *  <mailto:marshall at gotspeech.net> marshall at gotspeech.net |*
> > <mailto:marshall at gotuc.net> marshall at gotuc.net |(  904.342.6205
> >
> >
> >
> >  <http://www.microsoft.com/mvp> Description: Microsoft MVP Program
> >
>
>
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