DBL Technology GoIP User Manual page 32

3. Jitter Buffer
 Delay
 Min. Delay (ms)
 Max. Delay (ms)
4. Media QoS
5. Media Encryption
6. Symmetric RTP
7. Media NAT Traversal
8. Audio Codec Preference
http://www.dbltek.com
A jitter buffer is designed to remove the effects of jitter from the decoded voice stream,
buffering each arriving packet for a short interval before playing it out. This substitutes
additional delay and packet loss (discarded late packets) for jitter.
too small then an excessive number of packets may be discarded, which can lead to call
quality degradation. If a jitter buffer is too large, then the additional delay can lead to
conversational difficulty..
A fixed jitter buffer maintains a constant size whereas an adaptive jitter buffer has the
capability of adjusting its size dynamically in order to optimize the delay/discard
tradeoff.
Three modes of jitter buffer are supported:
1. Fixed - The fixed mode, which is the default mode, is a simple first in first out
mode, with a fixed jitter buffer delay.
2. Sequential - The sequential mode is also a fixed jitter buffer delay mode, but in
this mode the jitter buffer function looks at the packet timestamp for dropped or
out of sequence packet problems. The data packets are sorted based on the
packet timestamp
3. Adaptive - The adaptive mode optimizes the size of the jitter buffer delay and
depth in response to network conditions, in addition to the sequential mode
functions.
This specifies the fixed jitter delay for both Fixed and Sequential Jitter Buffer mode.
This specifies the minimum jitter delay for Adaptive Jitter Buffer mode.
This specifies the maximum jitter delay for Adaptive Jitter Buffer mode.
Similar to Signaling QoS, this parameter enables the QoS property for audio packets.
Both IP ToS (Type of Service) and DiffServe (Differentiated Service) method are
.
supported
Similar to Signaling Encryption (item 6 in this table), this parameter enables the
encryption for audio packets. Encryption methods supported are RC4 and ET263.
Network environment in some enterprise may require Symmetric RTP.
with your network administrator for further support.
This setting is not required if the target SIP server / PBX supports NAT traversal.
However, if your ISP blocks VoIP traffics, you could try to use Relay Proxy setting.
Depending on how your ISP blocks VoIP traffics, the Relay Server method may or may
not work in your network environment.
Two NAT Traversal methods are supported:
1. Stun Server – An external Stun Server is required. This allows the device to
obtain the public IP of the network used.
2. Relay Proxy – This is a proprietary method developed by DBL Technology. DBL's
Relay Proxy server must be used. A free copy of the Relay Proxy can be
download from DBL's website (www.dbltek.com). Please contact
techsupport@dbltek.com
Six types of audio codec are supported and they are summarized in the table below.
Codec
1. a-law
2. -law
3. G.729
4. G.729A
for further assistance if needed.
Raw Data Ethernet 802.3
Bandwidth (bps) Data Bandwidth
(bps)
64K ~ 85K
64K ~85K
8K ~39K
8K ~39K
GoIP User Manual
Fixed
If a jitter buffer is
60
None
None
Please check Disabled
selected)
None
All codecs are
enabled in the
order
preference
shown below.
a-law
-law
G.729
G.729A
G.729AB
G.723.1
(not
of
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