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PacketStar
®
PSAX 2300 Multiservice Media Gateway User Guide
, Issue 1
Release 9.0.0
Chapter 3 System Features
Voice Processing
Secure Telephone Unit Third Generation (STU-III) Secure Mode
This feature permits the DSP2D and DSP2E Voice Server modules to detect
the transition of a voice call from 8 kbps or 32 kbps mode to a STU-III secure
mode and to transmit the subsequent data stream in a compressed 32 kbps
rate. The feature then detects the end of the STU-III secure mode and reverts
to the previous voice mode. The STU-III secure mode option is supported on
CE-to-ATM PVC and CE-to-SPVC AAL2 connections only. The DSP2D and
DSP2E Voice Server modules must be set to a DSP mode of AlgoSet 6 in order
to use this feature.
Voice Path Assurance
In a circuit switched voice network, a test to verify continuity of the voice
channel can be made prior to connecting a voice call. This continuity test is
requested during the call establishment phase of a connection using SS7 sig-
naling. Voice circuit switches have been designed to recognize and respond to
requests for a continuity test and to take appropriate action when a failure
occurs. With the introduction of ATM trunking technology between circuit
switches, the ATM elements need to support the circuit switches with respect
to continuity testing (see Figure 3-23).
The Voice Path Assurance (VPA) feature supports voice quality testing over a
packet network for connections used in voice switched tandem networks.
The SS7 continuity test capability is implemented in the DSP2D voice server
for CE-to-CE (AlgoSet 5) , CE-to-AAL1 (AlgoSet 5), and CE-to-AAL2
(AlgoSet 6 only) connections and in the DSP2E voice server for CE-to-AAL2
(AlgoSet 6 only) connections. Non-multiplexed AAL2 connections are cur-
rently not supported.
Figure 3-23. End-to-End Continuity Check
Voice Gateway
Voice Gateway
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