asterisk users - Sep 2013 - RTP port ranges

Hello,

I have defined that I want to receive audio (RTP) on port 11500 till 
11954 (rtp.conf).

The same range I have defined in my firewall.

I now see that an IP-address gets blocked by my firewall because there 
are packets coming onto port 11955.


How come the client sends audio on port 11955 when I clearly define in 
my SDP-body that I want to receive audio on port range 11500 till 11954 ?

What makes the client choose this port number when it is not allowed ?



Kind regards,
Jonas.

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Normally you should open ports 10000-20000 udp



On 9/13/2013 11:37 AM, Jonas Kellens wrote:
> I now see that an IP-address gets blocked by my firewall because there 
> are packets coming onto port 11955.
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In article <5232DCBC.20803 at telenet.be>,
Jonas Kellens <jonas.kellens at telenet.be> wrote:
> 
> I have defined that I want to receive audio (RTP) on port 11500 till 
> 11954 (rtp.conf).
> 
> The same range I have defined in my firewall.
> 
> I now see that an IP-address gets blocked by my firewall because there 
> are packets coming onto port 11955.
> 
> 
> How come the client sends audio on port 11955 when I clearly define in 
> my SDP-body that I want to receive audio on port range 11500 till 11954 ?
> 
> What makes the client choose this port number when it is not allowed ?
An RTP connection typically uses a pair of adjacent ports. The even port
for the RTP stream, and the next port up (odd) for RTCP reports.

So when defining a port range, you should probably make the lower port
number even and the upper port number odd.

(so the default 10000-20000 is probably wrong too, and should be 10000-19999)

It also means that you should allow at least twice as many ports as the
number of simultaneous calls you want to handle.

Cheers
Tony
-- 
Tony Mountifield
Work: tony at softins.co.uk - http://www.softins.co.uk
Play: tony at mountifield.org - http://tony.mountifield.org