Nortel Networks TP-1610 SIP user manual TDM Tunneling, Implementation

Mediant 2000 SIP User’s Manual 8. Gateway Capabilities Description

8.8TDM Tunneling

The Mediant 2000 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 2000 (working without Proxy control) to receive voice and data streams from TDM (1 to 16 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 2000 opposite it (or several Mediant 2000 gateways, when point-to-multipoint distributions 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 2000.

8.8.1Implementation

When TDM Tunneling is enabled (‘EnableTDMOverIP’ is set to 1 on the originating Mediant 2000), the originating Mediant 2000 automatically initiates SIP calls from all enabled B-channels belonging to the E1/T1/J1 spans that are configured with the ‘Transparent’ protocol. 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 2000. The terminating Mediant 2000 gateway automatically answers these calls if its E1/T1 protocol is set to ‘Transparent’ (ProtocolType = 5) and 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 2000 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 2000 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 2000 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 5.8.5 on page 55) you can configure 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 enable RFC 2833 CAS relay mode (CASTransportType = 1).

Figure 8-1and Figure 8-2show an example of ini files for two Mediant 2000 gateways implementing TDM Tunneling for four E1 spans. Note that in this example both gateways are dedicated to TDM tunneling.

Version 4.4 149 July 2005