Release Link Trunk (RLT)
IMG 2020
Release Link Trunk is a technique for the Nortel DMS Variant where if there are two calls active on the IMG 2020 and they are bridged or looped together the resources on the IMG 2020 are being used inefficiently. With this feature the IMG 2020 has the ability to send specific facility messages back to the Nortel DMS and tell the switch to connect these two calls together so they are no longer active on the IMG 2020. This would effectively open up two b-channels that were initially being utilized. Release Link Trunk supports a portion of specification (NISA211_V801_NI-1, chapter 5-12 (Issue, August 98). See links under Related Topics below for more information on what is supported and how to configure.
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Two calls are in progress. The SIP side sends a REFER message to the IMG 2020, notifying the IMG 2020 to connect the two calls together.
After the call is bridged in the IMG 2020, the SIP leg is no longer connected. Call A and Call B are now routed through IMG 2020 as displayed below.
When Release Link Trunk is Enabled, the IMG 2020 will recognize that the call does not need to be routed through it. The bridged call is using resources on the IMG 2020 that could be used for other functions. The IMG 2020 would then send a request to Switch B (Nortel DMS) that the two independent calls be bridged together as shown below.
At this point, the call is being routed through Switch B and the IMG 2020 has released the call thereby freeing resources on both the IMG 2020 and Switch B.
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