User's Manual

Connection Type
A: FXS port of VG3300 Series
B, C: SIP Device (VG3300 Series, other brand SIP gateway. SIP phone...), Normal PSTN phone call
(special condition is described below)
Call waiting function works only on SIP call. So PSTN call works when it is transited as SIP call. If
Inbound transit call is configured on VG3300 (please refer to 10.9 Make Inbound Transit Call), then
Call Waiting function is available when user dials the SIP number of this VG3300 gateway itself. If
no inbound transit call function is configured, it is impossible to do call waiting function.
11.7. Target the Media (RTP)
For the SIP call passing through NAT, it is possible that the media would not deliver properly; owing
to the RTP contact information (IP address, port number) is different from original RTP packet. This
function selects different contact information for VG3300 to send RTP Packets to other SIP device
within far-end NAT. It designates whether to use the source contact information from the UDP/IP
header (Symmetric RTP) or the contact information specified within the packet (SDP) when the
gateway send RTP packet
Web Folder：ADVANCED\SIP COMMON, Default Value is SDP
Example 1: Via Symmetric RTP
The source contact information (IP, port number) of RTP packet is IP: 61.222.217.30, port number:
10000, but the SDP in the packet is IP: 10.13.6.18, port: 4000. In this case, please Use
Symmetric RTP
SDP in Packet
10.13.6.18
port: 4000
61.222.217.30
port: 10000
Network
VG3300 Series
(192.72.83.23,
port: 10000)
VG3300 tries the contact information from SDP first (IP:10.13.6.18, port number: 4000). If VG3300
finds that the contact information from SDP is different from the source contact information, then it
will try the source contact information, as the example above, use IP:61.222.217.30, port
number:10000. It makes SIP call successful.
Example 2: Via SDP (Default)
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