[asterisk-users] Why are 4 ports used for a single call?

[Gilles]

On Fri, 14 Jan 2011 17:29:26 -0500, Tom Rymes <trymes at rymes.com>
wrote:

>On 01/14/2011 4:19 PM, Bruce B wrote:
>> Also, to get the SIP very well as well, SIP uses both TCP/UDP 5060
>> right? and why are there recommendations of opening 5000-5082 UDP for
>> SIP along with 5060 TCP? Are there any "niceties" to that as well? maybe
>> video transmission stuff?
>
>More likely, it's because only one client behind NAT can use port 5060, 
>so other clients need to use other ports. Could be another reason, though.

FWIW, by default, GrandStream Budget phones use UDP 5004 for RTP.