Tdm Tunneling; Implementation - AudioCodes Mediant 1000 User Manual

12.2

TDM Tunneling

The Mediant 1000 TDM Tunneling feature allows you to tunnel groups of digital trunk
spans or timeslots (B-channels) over the IP network. TDM Tunneling utilizes the internal
routing capabilities of the Mediant 1000 (working without Proxy control) to receive voice
and data streams from TDM (1 to 4 E1/T1/J1) spans or individual timeslots, convert them
into packets and transmit them automatically over the IP network (using point-to-point or
point-to-multipoint gateway distributions). A Mediant 1000 opposite it (or several Mediant
1000 gateways, when point-to-multipoint distribution is used) converts the IP packets back
into TDM traffic. Each timeslot can be targeted to any other timeslot within a trunk in the
opposite Mediant 1000.

12.2.1 Implementation

When TDM Tunneling is enabled ('EnableTDMOverIP' is set to 1 on the originating Mediant
1000), the originating Mediant 1000 automatically initiates H.323 calls from all enabled B-
channels belonging to the E1/T1/J1 spans that are configured with the 'Transparent'
protocol (for ISDN trunks), or 'Ras CAS' (for CAS trunks). The called number of each call is
the internal phone number of the B-channel that the call originates from. The IP to Trunk
Group routing table is used to define the destination IP address of the terminating Mediant
1000. The terminating Mediant 1000 gateway automatically answers these calls if its E1/T1
protocol is set to 'Transparent' (ProtocolType = 5), or 'Raw CAS' (ProtocolType = 3 for T1
and 9 for E1) and the parameter 'ChannelSelectMode = 0' (By Phone Number).
Note: It is possible to configure both gateways to also operate in symmetric mode. To do
so, set 'EnableTDMOverIP' to 1 and configure the Tel to IP Routing tables in both Mediant
1000 gateways. In this mode, each gateway (after it is reset) initiates calls to the second
gateway. The first call for each B-channel is answered by the second gateway.
The Mediant 1000 monitors the established connections continuously, if for some reason
one or more calls are released, the gateway automatically reestablishes these 'broken'
connections. In addition, when a failure in a physical trunk or in the IP network occurs, the
Mediant 1000 gateways reestablish the tunneling connections as soon as the network
restores.
Note: It is recommended to use the keep-alive mechanism for each connection by
activating 'session expires' timeout, and using Reinvite messages.
By utilizing the 'Profiles' mechanism (refer to Section
the TDM Tunneling feature to choose different settings, based on a timeslot or groups of
timeslots. For example, you can use low-bit-rate vocoders to transport voice, and
'Transparent' coder to transport data (e.g., for D-channel). You can also use Profiles to
assign ToS (for DiffServ) per source, a time-slot carrying data or signaling gets a higher
priority value than a time-slot carrying voice.
For tunneling of E1/T1 CAS trunks set the protocol type to Raw CAS (ProtocolType = 3 / 9)
and enable RFC 2833 CAS relay mode (CASTransportType = 1).
Figure 12-2
implementing TDM Tunneling for four E1 spans. Note that in this example both gateways
are dedicated to TDM tunneling.
H.323 User's Manual
and Figure 12-3 show an example of ini files for two Mediant 1000 gateways
5.5.5 on page 106) you can configure
318
Mediant 1000
Document #: LTRT-83401