The following parameters in VXbuilder need to be altered to enable Secure Voice. Note: this assumes a configured and established network and secure phones are attached to VX via any of the supported physical interfaces (ISDN, SS7, CAS R2 or E&M, Analog).
Note this document only describes the basic, required settings; there are other settings in the system configuration that can affect secure voice. See the settings under Secure Relay in the General Telephony Settings settings, Secure Relay STU-III De-Scrambler option.
Edit Media Entry
This setting will be found in VXbuilder under the global system settings, titled "Modem/Fax Relay Mode" and needs to be set to T.38 Fax or Secure Relay.
Edit Media Entry
Edit Media Crypto Class
A media crypto class specifies one or more media-crypto attributes. Using the media crypto classes function controls the secure calls passthrough. The Secure Voice settings take effect at the start of the next call.
General Telephony Settings
The STU-III Scramble/Descrambler feature is enabled by default. You may have to disable the scrambler when troubleshooting older STU-III devices or STU-III like devices. Disabling the scrambler could result in large one way audio delays when in secure mode. It is not recommended that the user change this setting unless directed to by service or engineering.
The codecs used on all trunk groups involved with the Secure Voice call route need to have a valid non-conflicting audio codec and the STU codec, for example, G.723 AND STU) or (ANY).
The codecs used on the secure call route need to have a valid non-conflicting audio codec and the STU codec, for example, G.723 AND STU) or (ANY).
Operational and Performance Characteristics
Bandwidth usage for Secure Voice calls will vary greatly with the following factors:
- Base bandwidth of the secure data rate (9.6k, 4.8k, 2.4k etc.
- IP Packet overhead of each packet (IP + UDP + VTP)
- BESTflow Frame Packing Technology
- ECC (Error Correction used for Secure)
- Packet Dispatch Interval (VTPTimeout)/increased latency.
If you need help in determining the impact of these factors, contact your Sonus support representative.