[asterisk-users] configure SRTP port range?

[hw]

On 2/23/19 5:39 PM, Joshua C. Colp wrote:
> On Sat, Feb 23, 2019, at 12:17 PM, hw wrote:
> 
> <snip>
> 
>>
>>> Any source to UDP ports X to Y (10000 to 20000 by default) allow.
>>
>> Are you saying that the ports specified in rtp.conf ('rtpstart' and
>> 'rtpend') specify with ports asterisk uses regardless whether RTP or
>> SRTP is being used?  Is that why you speak of "media" (ports)?
>>
>> (That would have been and would answer my original question: Where to
>> specify the SRTP ports?)
> 
> Yes.

Cool :)

Maybe a hint like "these ports are used for SRTP as well" in the default 
rtp.conf would clarify this.  (I was actually looking for an srtp.conf 
to begin with ...)

>>> What you can't do is limit the rule based on the source of media, except for circumstances where you know for sure the source.
>>>
>>> Note that RTP ports in Asterisk aren't open all the time and only listen when a call is using it, and they also learn the source of media - blocking out other sources.
>>>
>>
>> ok
>>
>> After opening the ports specified in rtp.conf, both RTP and SRTP were
>> working in the test calls I made.  But:
>>
>> How do clients know which media ports to use?  Is asterisk telling them
>> that?
>>
>> I. e., can I (basically) rely on the clients to use the media ports in
>> rtp.conf, or did I just get lucky that by chance the clients happened to
>> use these ports when I made the test calls?
> 
> It's exchanged as part of call setup using SDP. SDP specifies where media should be sent, the codecs that can be used, and also controls hold/unhold. Each side provides SDP which is parsed, interpreted, negotiated, and used.
> 

Thank you very much!  So I got this to work; next step would be to try 
it with clients from outside the local network ... :)