Tag Archives: SDP

Strange issue with Sonicwall TZ 100/Asterisk 1.8 and a famous VOIP ISP

I want to tell a very strange issue occoured some weeks ago using pbx Asterisk 1.8, an router/firewall Sonicwall TZ 100 and a famous Voip ISP. The system has always worked fine until a couple of weeks ago (pls see … Continue reading

Posted in Asterisk | Tagged , , , , | Leave a comment

From SIP to RTP (Part 6) – The phone is ringing….

Real Case: Asterisk receive an external call A call from an external number to our pbx using a SIP trunk. Att: I have “sniffed” that traffic using tcpdump. In the next the Asterisk pbx is inside a LAN network, and … Continue reading

Posted in Asterisk, Voip | Tagged , , , , | Leave a comment

From SIP to RTP (Part 5) – Trunks & surroundings

Definition of Trunks Trunk lines are the phone lines coming into the PBX from the telephone provider. Trunking saves cost, because there are usually fewer trunk lines than extension lines, since it is unusual in most offices to have all … Continue reading

Posted in Asterisk, Voip | Tagged , , , , | Leave a comment

From Sip to RTP (Part 4) – Invite & Register friendship

INVITE Session Call Establishment Call Flow The UAC (Alice) sends an INVITE message to Bob (UAS). The UAS receives the request and responds with a 100 Trying. The UAS sends a 180 Ringing response to the UAC when the phone … Continue reading

Posted in Asterisk, Voip | Tagged , , , , | Leave a comment