Grandstream Networks GXV3275 Administration Manual page 51

SDP Bandwidth Attribute
H.264 Payload Type
H.263 Encoder Resolution
SRTP Mode
SRTP Key Length
Enable SRTP Key Life Time
Silence Suppression
Voice Frames Per TX
Sets the SDP bandwidth attribute. It can be selected from the drop down list.

Standard: use AS format in session level; use TIAS format in media level

Media Level: use AS format in media level

Session Level: use AS format in session level

None: no modifications in the session format
The default setting is "Media Level".
Note: Please do not modify this setting without knowing the session format supported
by the server. Otherwise, it might cause video decoding failure.
Specifies the H.264 codec message payload type format. The default setting is 99. The
valid range is from 96 to 127.
Configures the H263 encoder resolution which it will be used. Default setting is CIF.
Sets if the phone system will enable the SRTP (Secured RTP) mode. It can be selected
from dropdown list:

Disable

Enabled but not forced

Enabled and forced
SRTP uses encryption and authentication to minimize the risk of denial of service.
(DoS). If the server allows to use both RTP and SRTP, it should be configured as
"Enabled but not forced". The default setting is "Disable".
Configures all the AES (Advanced Encryption Standard) key size within SRTP. It can
be selected from dropdown list:

AES128&256 bit

AES 128 bit

AES 256 bit
If it is set to "AES 128&256 bit", the phone system will provide both AES 128 and 256
cipher suite for SRTP. If set to "AES 128 bit", it only provides 128-bit cipher suite; if set
to "AES 256 bit", it only provides 256-bit cipher suite. The default setting is
"AES128&256 bit".
Defines the SRTP key life time. When this option is set to be enabled, during the SRTP
call, the SRTP key will be valid within 2
key after this limitation. The default setting is "Yes".
Enables the silence suppression/VAD feature. If it is set to "Yes", when silence is
detected, a small quantity of VAD packets (instead of audio packets) will be sent during
the period of no talking. If set to "No", this feature is disabled. The default setting is
"No".
Configures the number of voice frames transmitted per packet. When configuring this,
it should be noted that the "ptime" value for the SDP will change with different
configurations here. This value is related to the codec used and the actual frames
transmitted during the in payload call. For end users, it is recommended to use the
default setting, as incorrect settings may influence the audio quality. The default setting
is 2.
GXV3275 Administration Guide
31
SIP packets, and phone will renew the SRTP
P a g e | 51