Chapter 1 Introducing Linksys IP Phones

Technology Background

Table 1-4 Linksys Phone Features (continued)

Feature

Description

 

 

Voice Activity

Voice Activity Detection (VAD) with Silence Suppression is a means of

Detection with Silence

increasing the number of calls supported by the network by reducing the

Suppression and

required bidirectional bandwidth for a single call. VAD uses a very

Comfort Noise

sophisticated algorithm to distinguish between speech and non-speech

Generation

signals. Based on the current and past statistics, the VAD algorithm decides

 

whether or not speech is present. If the VAD algorithm decides speech is not

 

present, the silence suppression and comfort noise generation is activated.

 

This is accomplished by removing and not transmitting the natural silence

 

that occurs in normal two-way connection. The IP bandwidth is used only

 

when someone is speaking. During the silent periods of a telephone call,

 

additional bandwidth is available for other voice calls or data traffic because

 

the silence packets are not being transmitted across the network. Comfort

 

Noise Generation provides artificially-generated background white noise

 

(sounds), designed to reassure callers that their calls are still connected

 

during silent periods. If Comfort Noise Generation is not used, the caller

 

may think the call has been disconnected because of the “dead silence”

 

periods created by the VAD and Silence Suppression feature.

 

 

Configurable Dial Plan

Linksys IP phones have three configurable interdigit timers:

with Interdigit Timers

Initial timeout (T)—Handset off hook; no digit pressed yet.

 

 

Long timeout (L)—One or more digits pressed, more digits needed to

 

reach a valid number (as per the dial plan).

 

Short timeout (S)—Current dialed number is valid, but more digits

 

would also lead to a valid number.

 

 

Report Generation and

Linksys IP phones report a variety of status and error reports to assist service

Event Logging

providers in diagnosing problems and evaluating the performance of their

 

services. The information can be queried by an authorized agent, using

 

HTTP with message-digest authentication, for instance. The information

 

may be organized as an XML page or HTML page.

 

 

Syslog and Debug

Linksys IP phones support detailed logging of all activities for further

Server Records

debugging. The debug information may be sent to a configured Syslog

 

server. Linksys IP phones provide configuration settings that determine the

 

type of activity/events that should be logged as, for example, a debug level

 

setting.

 

 

Dynamic Payload

When no static payload value is assigned per RFC 1890, Linksys IP phones

 

can support dynamic payloads for G.726.

 

 

Call Statistics and

The statistics collected by Linksys IP phones during normal operation

Reporting

statistics are available in the Info tab. Line status is reported for each line (1

 

and 2). Each line maintains up to 2 calls: Call 1 and 2.

 

 

Technology Background

This section provides background information about the technology and protocols used by the phone:

Session Initiation Protocol, page 1-9

 

Linksys IP Phone Administrator Guide

1-8

Firmware Version 5.1

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Linksys SPA 900 SERIES manual Technology Background, Session Initiation Protocol