Eusso 2 & 4 Port VoIP Gateway, Руководство пользователя

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ITG User’s Guide
Hunt Group Table
The hunt group table maps a hunt group to a list of destinations. Hunt group sample
Group id Type #Members Member ids
----------------------------------------------------------------------------
1 2 1 1
3 2 1 2
5 2 1 4
11 2 1 11
12 2 1 12
Destination Table
The destination table maps a destination to a telephony port or the IP address of a remote
ITG.
Destination table sample
Dest id Mode Destination
-------------------------------------------------------
1 Local PORT = 0
3 Local PORT = 2
5 Local PORT = 4
11 H.323 Dest = 192.168.0.55/1720 TCP
12 DNS Dest = abc0021.dyndns.org /1720 TCP
3.6 DTMF Relay
Voice from PSTN is compressed by the ITG before sending across the IP network and then
decompressed by the destination ITG. The voice coders supported by the ITG are designed
for ideally compressing and decompressing human voice. If the compression /
decompression process is performed on DTMF tone which needs to be conveyed across IP
network, distortion might be too significant to be not cognizable in the receiving end. To
overcome the shortcoming that the voice coders can not perfectly encode DTMF tone, the
ITG encodes DTMF tone into special packets. The packets are then sent to the destination
ITG via a separate IP connection. The destination ITG decodes the packets, generates the
DTMF tone, and then sends the tone to the PSTN. The way the ITG handles DTMF tone is
so called DTMF relay.
The ITG handles DTMF relay per H.323 specifications. Certain third party VoIP devices
may handle DTMF relay per IMTC standard. For the ITG to interoperate with those VoIP
devices, users need to specify which remote VoIP devices uses IMTC conforming DTMF
relay technique. Refer to CLI command set h323 imtc_dtmf {add|del}
ip_addr on Chapter 8
for detailed information on how to select DTMF relay mode.
3.7 Voice Codecs
Voice codecs supported by the ITG include G.711, G.723.1 5.3kbps, G.723.1 6.3kbps and
G.729 AB. When setting up a call, two ITG automatically negotiate with each other until an
agreed upon codec is determined.
ITG Concepts
9