Introduction To Voip - 3Com MSR 50 Series Configuration Manual

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Introduction to VoIP

V IP O
O VERVIEW
This document is organized as follows:
"VoIP Overview" on page 2243
■
"Voice Subscriber Line Configuration" on page 2245
■
"Voice Entity Configuration" on page 2265
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The voice over IP (VoIP) network is an IP-based packet switched network. After
digitization, compression, and packetization, traditional analog voice signals are
encapsulated into frames for transmission over the IP network.
In a broad sense, VoIP refers to a way to carry data, voice, fax, image and other
multimedia services over an IP data network. In a narrow sense, VoIP refers to a
way to carry the voice service over an IP data network. The well-known IP phone is
a typical VoIP application.
Table 75 makes a comparison between plain old telephone service (POTS) with
VoIP.
Table 75 Comparison between POTS and VoIP
POTS
Based on circuit switching
Physical connection. The two parties in
conversation each seize a physical connection.
Subject to constraints of communication
procedure, transmission rate, and
encoding/decoding scheme
High communication cost
VoIP
Based on packet switching
Virtual connection. The two parties in
conversation share a physical connection.
Providing value-added services by
controlling signaling
Low communication cost