FreePBX + Voip.ms
SIP Trunk Provider Registration
FreePBX Trunk & Local Extensions
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Grandstream VoIP Phone & My Cell Phone
SIP Session Lifecycle in WireShark
Packet 111 (INVITE): The Call Request
The FreePBX server sends a secure request with the correct account credentials to VoIP.ms to start the outbound call.
Packet 116 (100 Trying): The Network Acknowledgment
VoIP.ms replies to the FreePBX server to say, "We got your message and are working on routing the call right now."
Packet 281 (183 Session Progress): The Ringing Signal
VoIP.ms opens up the audio channel early so I can hear my cell phone ringing on my Grandstream desk phone.
Packet 374 (200 OK): Start of Call
The exact moment my cell phone answers the call, opening up the live, two-way voice stream back to my Grandstream phone.
Packet 13366 (BYE): End of Call
VoIP.ms sends a message to my FreePBX server to tear down the connection the exact second the cellular phone hangs up.
Packet 13367 (200 OK): Call Closed
My FreePBX server sends a final confirmation back to VoIP.ms showing the call successfully finished and the network line is completely cleared out.
RTP Stream and Network Packet Analysis
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G.711 Call Performance Stats
Audio Codec: G.711 PCMU
Voice Payload Size: 160 bytes
Network Bandwidth: 80 kbps
Average Jitter: 0.16 ms (<20 ms)
Maximum Jitter: 0.50 ms (<30 ms)
Total Packets: 1,581 packets
Packet Loss: 0% (<1%)