User`s manual
MP-1xx H.323
MP-1xx H.323 User’s Manual 154 Document #: LTRT-65104
2. Set parameter DTMFTransportType = Transparent.
8.3.1 Overview of In-Band DTMF Transport Types
The MP-1xx gateway controls the way DTMF digits are transferred in-band (as part of the audio
stream) using the DTMFTransport configuration parameter.
Note that this parameter is automatically updated in the first four methods described in the
previous section and therefore shouldn’t be changed, while, for the fifth method (in-band DTMF) it
should normally be set to Transparent.
The following four modes are supported:
• DTMFTransportType = 0 (Mute DTMF). In this mode DTMF digits are erased from the audio
stream and are not relayed to the remote side. Instead silence is sent in the RTP stream.
• DTMFTransportType = 2 (Transparent DTMF). In this mode DTMF digits are left in the audio
stream and the DTMF relay is disabled.
• DTMFTransportType = 3 (RFC 2833 DTMF Relay). In this mode, DTMF digits are relayed to
the remote side using the RFC 2833 Relay syntax.
8.4 Configuring the Gateway’s Alternative Routing
(based on Connectivity and QoS)
The Alternative Routing feature enables reliable routing of Tel to IP calls when a Gatekeeper isn’t
used. The MP-1xx gateway periodically checks the availability of connectivity and suitable Quality
of Service (QoS) before routing. If the expected quality cannot be achieved, an alternative IP
route for the prefix (phone number) is selected.
8.4.1 Alternative Routing Mechanism
When a TelIP call is routed through the MP-1xx gateway, the call’s destination number is
compared to the list of prefixes defined in the Tel to IP Routing table (described in Section
5.8.4.2
on page 74). The Tel to IP Routing table is scanned for the destination number’s prefix starting at
the top of the table. When an appropriate entry (destination number matches one of the prefixes)
is found; the prefix’s corresponding destination IP address is checked. If the destination IP
address is disallowed, an alternative route is searched for in the following table entries.
Destination IP address is disallowed if no ping to the destination is available (ping is continuously
initiated every 7 seconds), when an inappropriate level of QoS was detected, or when DNS host
name is not resolved. The QoS level is calculated according to delay or packet loss of previously
ended calls. If no call statistics are received for two minutes, the QoS information is reset.
The MP-1xx gateway matches the rules starting at the top of the table. For this reason, enter the
main IP route above any alternative route.
8.4.2 Determining the Availability of Destination IP Addresses
To determine the availability of each destination IP address (or host name) in the routing table,
one (or all) of the following (configurable) methods are applied:
• Connectivity – The destination IP address is queried periodically (currently only by ping).
• QoS – The QoS of an IP connection is determined according to RTCP statistics of previous
calls. Network delay (in msec) and network packet loss (in percentage) are separately
quantified and compared to a certain (configurable) threshold. If the calculated amounts (of
delay or packet loss) exceed these thresholds the IP connection is disallowed.