ZyXEL Communications P-324 User's Guide download pdf (Page 171)

P-2602HWNLI User’s Guide

Chapter 11 Voice 171

11.3.1 RTP

When you make a VoIP call using SIP, the RTP (Real time Transport Protocol) is used to

handle voice data transfer. See RFC 1889 for details on RTP.

11.4 SIP ALG

The ZyXEL Device is a SIP Application Layer Gateway (ALG). A SIP ALG allows VoIP calls

to pass through NAT by examining and translating IP addresses embedded in the data stream.

When a VoIP device behind the ZyXEL Device registers with the SIP register server, the

ZyXEL Device translates the device’s private IP address inside the SIP data stream to a public

IP address. You do not need to use STUN with a VoIP device that is behind the ZyXEL

Device.

11.5 Voice Coding

A codec (coder/decoder) codes analog voice signals into digital signals and decodes the digital

signals back into voice signals. The ZyXEL Device supports the following codecs.

• G. 7 11 is a Pulse Code Modulation (PCM) waveform codec. PCM measures analog signal

amplitudes at regular time intervals and converts them into bits. G.711 provides very good

sound quality but requires 64kbps of bandwidth.

• G. 7 2 9 is an Analysis-by-Synthesis (AbS) hybrid waveform codec that uses a filter based

on information about how the human vocal tract produces sounds. G.729 provides good

sound quality and reduces the required bandwidth to 8kbps.

SIP Service

Domain

Enter the SIP service domain name. In the full SIP URI, this is the part after the @

symbol. You can use up to 127 printable ASCII Extended set characters.

Send Caller ID Select this if you want to send identification when you make VoIP phone calls.

Clear this if you do not want to send identification.

Authentication

User Name Enter the user name for registering this SIP account, exactly as it was given to you.

You can use up to 95 printable ASCII characters.

Password Enter the user name for registering this SIP account, exactly as it was given to you.

You can use up to 95 printable ASCII Extended set characters.

Apply

Click this to save your changes and to apply them to the ZyXEL Device.

Cancel Click this to set every field in this screen to its last-saved value.

Advanced Setup Click this to edit the advanced settings for this SIP account. The Advanced SIP

Setup screen appears.

Table 57 SIP > SIP Settings

LABEL DESCRIPTION

1 2 ... 166 167 168 169 170 171 172 173 174 175 176 ... 441 442

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ZyXEL Communications P-324 User's Guide Page 171