ZyXEL Communications MAX208M2W SERIES, User Manual

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Chapter 9 The VoIP General Screens
MAX208M2W Series User ’ s Guide
136
The following table describes the labels in this screen.
9.2.1 QoS
This section describes the features of the Quality of Service (QoS) screen.
Table 47
VoIP > General > Media
LABEL DESCRIPTION
Port Range
Media Port Start
Media Port End
Enter the listening port number(s) for RTP traffic on the MAX208M2W
Series, if your VoIP service provider gave you this information.
Otherwise, keep the default values.
To enter one port number, enter the port number in the both Media
Port Start and Media Port End fields.
To enter a range of ports, enter the beginning port number of the range
in the
Media Port Start field and the ending port number in the Media
Port End field.
Codec Packetization Time Settings
G.711, G.729
Select the type of voice coder/decoder (codec) that you want the
MAX208M2W Series to use.
G.711 provides high voice quality but
requires more bandwidth (64 kbps). G.729 requires only 8 kbps.
Advanced
Voice Jitter
Buffer Type
Voice jitter is a variation in delay of RTP packets delivery. This could
cause strange sound effects. The MAX208M2W Series can utilize the
following types of jitter buffer to minimize the effects of jitter.
Dynamic - Jitter buffer size is dynamically changed by RTP packets
delivery status.
Static - Jitter buffer size is fixed.
Voice Jitter
Buffer Length Select the maximum number of milliseconds of voice traffic the
MAX208M2W Series can help to smooth out the jitter in order to ensure
good voice quality for your conversations.
Packet Loss
Concealment Packets may be dropped due to an overwhelming amount of traffic on
the network. Some degree of packet loss will not be noticeable to the
end user, but as packet loss increases the quality of sound degrades.
Select this to have the MAX208M2W Series to improve the voice quality
when packet loss occurrs.
T.38 Static
Jitter Length T.38 is an ITU-T standard that VoIP devices use to send fax messages
over the Internet.
Select the number of milliseconds for the jitter buffer size used for
transmitting T.38 fax messages.