Use the Early Media window to configure parameters related to early media processing for a specified SIP trunk group.
To View and Edit Early Media Parameters
On the SBC main screen, go to Configuration > System Provisioning > Category: Trunk Provisioning > Trunk Group > SIP Trunk Group > SIP Trunk Advanced > SIP Trunk - Media - Advanced > Early Media or
All > Address Context > Zone > SIP Trunk Group > Media > Early Media
The Early Media window is displayed.
Use the drop-down boxes to select an Address Context, Zone and SIP Trunk Group.
Figure 1: Early Media Window
The following fields are displayed:
Table 1: Early Media Parameters
Parameter | Description |
---|---|
Method | Method used to provide early media. Additional options appear based on your choice for Method.
|
Forking Behaviour | Use this parameter to identify the method to provide early dialog media selection.
|
Make the required changes and click Save.
P-Early-Media and Delayed RBT
To use the Force Local Ring Back Tone (FLRBT) feature, set the PSX flag DelayedRBTWithToneContinuation
to enabled
. The flag is available under the entity Tone Generation Criteria
> Delayed RBT
in the PSX.
- To create a Tone Generation Criteria entity with the flag
DelayedRBTWithToneContinuation
:create Tone_Generation_Criteria_Data Tone_Generation_Criteria_Id <string> Sequence_Number <int> [Response_Code <short>] [Attributes <int>] [Ingress_Tg <string>]
- To update a Tone Generation Criteria entity with the flag
DelayedRBTWithToneContinuation
:update Tone_Generation_Criteria_Data Tone_Generation_Criteria_Id <string> Sequence_Number <int> [Response_Code <short>] [Attributes <int>] [Ingress_Tg <string>]
- To delete a Tone Generation Criteria entity with the flag
DelayedRBTWithToneContinuation
:delete Tone_Generation_Criteria_Data Tone_Generation_Criteria_Id <string> Sequence_Number <int>
For more information on the flag DelayedRBTWithToneContinuation
, refer to the PSX document Tone Generation Criteria Screen.
When a caller sends a SIP INVITE
to the SBC (irrespective of the presence of "P-Early-Media: supported
" header in the Session Description Protocol (SDP) of the INVITE
), the SBC adds P-Early-Media header in its 18x
(180
or 183
) response towards ingress call leg only if:
The SBC monitors and detects early media from the egress call leg.
NoteThe SBC has an "observation" window for monitoring the stream of RTP packets. It also has a "silence" window before it restarts monitoring, to reject RTP packets from a previous announcement.
The SBC plays a Ring Back Tone (RBT).
NoteThe SBC plays LRBT only if it does not receive any early media from the egress call leg at the end of a monitoring cycle. If the SBC starts playing LRBT, it continues to play even if it detects RTP in the subsequent monitoring cycles, or exchanges a new set of SDP answers with the egress call leg.
When the SBC receives an UPDATE from the egress call leg, and the caller (ingress call leg) does not support UPDATE, the SBC continues to feed tone in the same codec. When the ingress call leg supports UPDATE, the SBC feeds tone in a modified codec after a successful offer-answer negotiation.
If the egress call leg responds with P-Early-Media header in its 18x response, the SBC transparently relays it to the ingress call leg.