ZyXEL Communications 802.11g Wireless ADSL2+ 4-port VoIP IAD P-2602HWNLI - Manual (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.711 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.729 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