PLANET VIP-000 - Manual (Page 25)

VIP User ’s Manual
VIP Concepts
11
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
Destination Table
The destination table maps a destination to a telephony port or the IP address of a remote VIP.
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 = planetvip.dyndns.org /1720 TCP
3.6 DTMF Relay
Voice from PSTN is compressed by VIP before sending across the IP network and then decom-
pressed by the destination VIP. The voice coders supported by VIP are designed for ideally com-
pressing and decompressing human voice. If the compression / decompression process is per-
formed on DTMF tone which needs to be conveyed across IP network, distortion might be too sig-
nificant to be not cognizable in the receiving end. To overcome the shortcoming that the voice cod-
ers cannot perfectly encode DTMF tone, VIP encodes DTMF tone into special packets. The pack-
ets are then sent to the destination VIP via a separate IP connection. The destination VIP decodes
the packets, generates the DTMF tone, and then sends the tone to the PSTN. The way VIP han-
dles DTMF tone is so called DTMF relay.
VIP handles DTMF relay per H.323 specifications. Certain third party VoIP devices may handle
DTMF relay per IMTC standard. For VIP 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 for detailed information on how to select DTMF re-
lay mode.
3.7 Voice Codecs
Voice codecs supported by VIP include G.711, G.723.1 5.3kbps, G.723.1 6.3kbps and G.729 AB.
When setting up a call, two VIP automatically negotiate with each other until an agreed upon codec
is determined.