Expert Documentation

To enable fax over G.711 for a SIP subscriber, the following PBX configuration directives must
be followed:
- “Fax 2/3” services associated to the subscriber must be enabled (in OMC, Subscriber
>Services)
- VoIP VAD must be disabled (in OMC, Voice Over IP >DSP)
- If a SIP trunk is configured on the PBX, Fax over G.711 must be configured in gateway
parameters in the ARS (in OMC, Numbering >Automatic Route Selection/Gateway
Parameters). The remote gateway MUST support fax over G.711. (Reminder : the use of
voipnwaddr/inhibit_t38 flag is deprecated).
On the other hand, in the media gateway configuration, the codec to use along with the PBX
must be forced to G.711 (alaw or µlaw), and VAD must be disabled.
6.4.2.3.21 Supplementary Services
Hold
A remote party can put on hold a local user through a public SIP trunk group by:
- Sending a Re-INVITE with an IP address set to 0.0.0.0 or media attribute set to "sendonly".
The local music on hold is played by the Alcatel-Lucent OmniPCX Office Communication
Server to the user put on hold.
- Sending a Re-INVITE with a valid IP address.
The remote party plays its own music on hold. Hold is transparent to the Alcatel-Lucent
OmniPCX Office Communication Server.
A local user can put on hold a remote party through a public SIP trunk group. The local music
on hold is played by the Alcatel-Lucent OmniPCX Office Communication Server to the remote
party put on hold. A Re-INVITE is transmitted with a valid media IP address.
Call Forwarding
Call forwarding is performed by joining the two calls.
Call forwarding with signaling path optimization is not supported.
Media optimization can be performed through the RTP direct mechanism.
The 3xx message is not used:
- The Alcatel-Lucent OmniPCX Office Communication Server does not send a 3xx message.
- The provider must not send a 3xx message. Such a message is rejected with a
503.Service Unavailable message.
Transfer
Transfer is performed by joining the two calls. The Re-INVITE method is used.
Transfer with signaling path optimization is not supported.
Media optimization can be performed through the RTP direct mechanism.
RFC 3515, 3891 and 3892 are not supported on public SIP Trunking.
- The Alcatel-Lucent OmniPCX Office Communication Server does not use the REFER
method
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