About Voice over IP (VoIP)
Establishing a Before voice traffic can pass between the voice ports over the network, the source IP
Sessionmust establish a TCP and UDP session with the destination IP node. Each session is uniquely identified by a source IP address, destination IP address, source port number, and destination port number. The source and destination node exchange the following call packets to establish a session:
Stage | Packet Transferred | Description |
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1 | ACP Call Request | The voice port sends an ACP (Adjacent |
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| Channel Protocol) Call Request to inform |
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| the source IP node that it wishes to send |
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| voice over the network to the destination |
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| voice port. |
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| Open UDP | When a voice port attempts to make a call, |
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| the Source IP node opens a UDP channel. |
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2 | TCP Call Request | To open a session, the source IP node sends a |
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| TCP call request to the destination IP node. |
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| TCP Call Accept | The destination IP node responds to the Call |
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| Request by sending a Call Accept, and |
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| establishes a TCP session. |
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Establishing a After opening a TCP and UDP session, the source node must establish an SoTCP
Connectionconnection with the destination IP node. Each TCP session support multiple connections or SVCs. A unique connection identifier identifies each connection multiplexed on a TCP session. The source and destination IP nodes exchange the following call packets to establish a connection:
Stage | Packet Transferred | Description |
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1 | SoTCP Internal Call | The source IP node sends an internal |
| Request | SoTCP call request packet with the UDP |
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| port number included, to the destination IP |
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| node. The destination IP node examines the |
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| facilities field in the header to determine |
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| the presence of voice traffic. If voice traffic |
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| is present, the destination IP node opens a |
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| UDP channel. |
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| The destination IP node uses the UDP port |
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| number in the internal SoTCP call request |
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| packet to identify the destination port for |
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| UDP packets. |
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2 | ACP Call Request | The destination IP node sends an ACP call |
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| request to the remote voice port. |
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| ACP Call Accept | To accept the call, the voice port responds |
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| with an ACP Call accept packet. |
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6 | Voice Over IP |
