I'm having a problem with my recent Asterisk 11.17 installation. I have a couple Polycom phones, a couple ATAs, and softphones running on wifi tablets. The problem is that some of the stations don't work. Well, none of them work perfectly, but some better than others.
The one that work better miss a fraction of a second of the incoming audio, and then all is well.
The ones that work less well burp out that first fraction of a second, and then go silent, which is really limiting to their usefullness as phones.
The Asterisk is running on a Slackware Linux system which also serves as my Internet gateway/firewall machine. The telephones are all on the localnet, and the other port of the
server is directly on the real Internet.
Looking at a Wireshark trace of the external net, I see Asterisk issuing a couple of INVITE’s a tenth of a second apart - bangbang! These INVITEs specify media port 22454. The remote system then starts sending a stream of RTP packets from port 21972 to port 22454. This continues for about 30 packets. Then Asterisk issues another INVITE, specifying a different local port - this time, 16408.
The remote system then, without missing a beat, continues its RTP stream, only now to dest port 16408.
On the localnet side, RTP packets to my “good” ATA only start at 2.25 seconds into the trace. These
packets all have a sensible 164xx port numbers. It looks to me like Asterisk is eating those first
31 RTP packets ( with 22454 dest port ) and throwing them into the bit bucket.
Anybody seen similar? Mighty Google has come up dry…