Specifications

VoiceFinder VoIP Gateway Configuration Guide (APOS 2.0) Release Version 3.1
AddPac Technology Co., LTD
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3.10.5.4. media-channel
Media channels are RTP/RTPC path for VoIP communication. In other words, media channel can
be divided by transmit channel and receive channel for VoIP communication.
This feature configures a point of time to enable transmit channel.
Use this command to set up and enable media channel type.
media-channel {early| late}
no media-channel
3.10.5.4.1. Syntax
Keyword / Argument Description
Early Opens transmit channel when 18X SDP is received after
INVITE is transmitted
late Does not open transmit channel, even 18X SDP is received
after INVITE is transmitted, opens it only when 200 OK is
received
3.10.5.4.2. Command Default
No default behavior or value
3.10.5.4.3. Command Modes
SIP configuration
3.10.5.4.4. Usage Guidelines
When the gateway operates under PAT/NAT environment, VoIP equipment from the other side
provide ring back tone(Color Ring included) by inband (RTP), ringback tone fails to reach the
gateway under the private environment . The cause is same as enable-ping.
To take compliment measures of this problem, the gateway under the private environment
transmits INVITE, transmit channel opens when to receive 18X SDP, a port table is created in
PAT/NAT server, inband right back tone can be heard as a result.
The first type is the default mode. Transmit cannel opens to only 183 progress SDP after
INVITE is transmitted. Transmit channel does not open even 180 SDP is received.
The second type is early mode. Transmit channel opens when 18X SDP is received after INVITE
is transmitted.
18X SDP means whether SDP presents in 180 ring message or in 183 progress message.