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This page
isprovides a brief overview of the various direct Media Call Flows.
Multiple call
-flows can lead to Direct Media (DM) call processing. However, the three basic forms of DM call flows are explained in this section:
- Basic Direct Media Call
- Direct Media using X-dmi
- Direct Media via Antitrombone
For more information, refer to Configuring Direct Media between Endpoints.
Direct Media Overview
The three types of DM call - flows the SBC supports are listed below:
- Pass-Thru (PT) Calls
- The SBC publishes its own media IP address in offer/answer, so that, media flows through the SBC towards the endpoints.
- The SBC uses XRES and BRES Resources for this call-flow.
- Resource chain for pass-through call.
- Transcoded Calls
- The SBC publishes its own media IP address in offer/answer.
- This is when media terminates at the SBC from one endpoint and the SBC transcodes the media using DSP from one type of codec to the other.
- The SBC uses XRES, DRES and BRES resources for this call-flow.
- Resource chain for transcodec calls
- Direct Media (DM) Calls
- The SBC publishes the endpoint IP address to both the endpoints, so that the media flows between the endpoints and not through the SBC.
- The SBC uses XRES and BRES resources for this call-flow; however, there is no bandwidth usage.
Types of Direct Media (DM) Call
-Flows Supported by the SBC
Basic Direct Media Call
This requires the following configurations:
Ingress:
- At SIP Trunk Group level:
directMediaAllowed
enabled - At Packet Service Profile level:
useDirectMedia
enabled
Egress:
- At SIP Trunk Group level :
directMediaAllowed
enabled - At Packet Service Profile level:
useDirectMedia
enabled
The Direct Media Zone-ID should be the same for ingress and egress zones.
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Direct Media using X-dmi
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- X-dmi was introduced to support Direct Media for call flows with SIP Server or an Application server routing the calls.
- X-dmi is a Ribbon-specific header, which contains encrypted SDP attributes.
- In order to support Direct Media for NAPT-ed endpoints, X-dmi was extended to include 3 new the following fields:
- z – Direct Media Zone ID
- b – Bit Mask to indicate below information
- p – Signaling IP address of Endpoint
- a – Address Context of the endpoint
The following configurations are needed to support X-dmi calls:
Access Side:
At SIP Trunk Group level
directMediaAllowed
enableddirectMediaAllowedBehindNat
enabled
- At Packet Service Profile level
-
useDirectMedia
enabled
-
Core Side (towards Application Server):
At IPSP level
sendDirectMediaInfoInSdpAttribute
enabled
- At Packet Service Profile level
useDirectMedia
enabled
The following additional configurations are needed to support X-dmi call with NAPT-ed endpoints.
Configuring Direct Media Between Endpoints Behind Same NAT
Access Side:
- At SIP Trunk Group level
- directMediaAllowed enabled
- directMediaAllowedBehindNat enabled
- At Packet Service Profile level
-
useDirectMedia
enabled
-
Core Side (towards Application Server):
- At IPSP level
- sendDirectMediaInfoInSdpAttribute enabled
- At Packet Service Profile level
useDirectMedia
enabled
Configuring Direct Media Between Endpoints Behind the Different NAT
Access Side:
- At SIP Trunk Group level
directMediaAllowed
enableddirectMediaAllowedBehindNat
enabledsdpTransparencyState
disabled
- At Packet Service Profile level
useDirectMedia
enabled
Core Side (towards Application Server):
- At IPSP level
sendDirectMediaInfoInSdpAttribute
enabled
- At Packet Service Profile level
useDirectMedia
enabled
- At Address Context level
- Creating the table
dmNatPrefix
onaddressContext
- Adding the signaling IP Address of NAT Box, which can have direct media among them.
- Creating the table
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