About Voice over IP (VoIP)
SoTCP Operation
Introduction | This section describes the operation of SoTCP protocol. SoTCP provides the |
| encapsulation method for carrying voice traffic over an IP network. |
SoTCP Packet The SoTCP protocol terminates voice traffic received from a voice device and
Formatprefixes the traffic with a
3 or 4 Byte SoTCP Header
Data
| Figure 3. SoTCP Packet Format |
| The SoTCP header contains information that will allow a destination IP node to |
| reconstruct the voice packet at the remote end. |
Transport |
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To carry voice traffic over IP, SoTCP uses two Transport layer protocols, the | |
Mechanism | Transport Control Protocol (TCP) and User Datagram Protocol (UDP). |
Transport | Traffic Carried | Description |
Layer |
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Protocol |
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TCP | Voice Signalling Traffic | SoTCP uses TCP to carry voice signalling |
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| traffic because TCP provides reliable, |
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| sequenced packet delivery. Voice |
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| signalling traffic encapsulated by SoTCP |
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| must arrive at the destination node without |
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| error or delay. TCP implements error |
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| recovery for duplicate or lost packets. |
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UDP | Audio and Fax | SoTCP transports audio and fax traffic |
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| over UDP session. Unlike TCP, UDP |
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| provides fast and simple transaction |
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| services with minimal protocol overhead. |
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| UDP provides a |
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| mechanism only and does not ensure |
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| reliable delivery. |
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Each TCP or UDP session may carry multiple switched virtual circuits (SVCs).
SoTCP uses SVC call setup and routing procedures to establish voice SVCs.
4 | Voice Over IP |
