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Audio Transcode and Video Relay

The SBC SWe Cloud inter-operates with a third-party transcoding platform called Media Resource Function (MRF) to transcode audio and relay video/T140.

Note

Only the SBC SWe Cloud on OpenStack (D-SBC) supports this feature. 


 

The SBC SWe Cloud supports the following functionality:

  • Relaying both audio and video streams.
  • Relaying audio, video and T140 streams.
  • Audio transcode through MRF and video relay.
  • Audio transcode through MRF and video/T140 relay.
  • Audio transcode through MRF and T140 relay.

Note

The SBC SWe Cloud supports this functionality only for MRF-transcoded calls on D-SBC platforms.

Note

If the Packet Service Profile is configured as "transcode-only", the SBC SWe Cloud transcodes the audio and relays video/ T140.

 

SBC SWe Cloud Limitations

  • Audio-less calls are not supported.
  • Video licenses are not supported. Thus, only one video stream is supported.
  • Only video and T140 streams among the non-audio streams are supported.

For more information on CLI changes and CDR changes, refer to:

Prerequisites to Invoking MRF

Note

The first three activities below cause the D-SBC to include DSP when invoking MRF.

 

  1. Configure MRF Profile in S-SBC
  2. Configure Private LIF Groups in M-SBC
  3. Enable transcoding at the Packet Service Profile (refer to Packet Service Profile - CLI).
  4. Create a Path Check Profile, ARS profile, and CAC profile during the initial configuration

Note

Sonus recommends to not configure Path Check Profile and SIP ARS Profile on the same peer to avoid unexpected results. As a general rule, the Path Check Profile is configured on the access leg where there is less traffic, and the ARS Profile is configured on the peer leg where there is continuous traffic. 

Configure MRF Profile in S-SBC

This configuration example explains how to configure the MRF cluster profile in the S-SBC. The MRF servers are configured as FQDN or the IP address is decided by Routing Type configured in the MRF Profile.

Click to expand...

Configure Private LIF Groups in M-SBC

This configuration example explains the CLI command required to configure the MRF cluster profile in M-SBC.

Click to expand...

 

Create a Path Check Profile, ARS profile, and CAC Profile During Initial Configuration

 

Path Check Profile

The Path Check Profile specifies the conditions that constitute a connectivity failure, and in the event of such a failure, the conditions that constitute a connectivity recovery.

  • For more information on path check, refer Service Profiles - Path Check Profile
  • For more information on creating IP Peer, refer to System Provisioning - Ip Peer for GUI or Zone - IP Peer - CLI.

    Note

    If using an IP address, create different IP Peers for each IP addresses configured in MRF cluster profile as MRF IP address and attach the Path Check Profile.

    If using an FQDN, create the IP Peer with FQDN and attach the Path Check Profile.

ARS Profile

The Address Reachability Service (ARS) determines whether a server is reachable, able to blacklist a server IP address when unreachable, and remove the server from blacklist state. ARS profiles can be created to configure blacklisting and recovery algorithm variants. For more information, refer to Service Profiles - Sip Ars Profile (EMA) or SIP ARS Profile - CLI.

Create an ARS profile and attach to the MRF TG as configured in the cluster profile. The ARS feature controls the congestion to handle the 503 response.

CAC Profile

 

Invoking MRF Server

In a cluster profile, you can configure the routing type for FQDN or a list of IP addresses. If FQDN is chosen, the FQDN resolves into a list of IP addresses.

If the MRF profile is configured with a list of MRF server IP addresses and a call is routed to MRF server(s) as follows:

  • S-SBC tries to connect to the configured MRF server IP addresses in a round-robin fashion.
  • If any failure/no response is received from an MRF server for a specific IP address, the same IP address is blacklisted. When blacklisted, S-SBC continuously sends an option message to MRF server to check whether the IP is active/inactive. Once the IP is active, S-SBC removes the IP address from the blacklist state and tries to connect to the same IP when the next call is routed to MRF Server.
  • S-SBC tries for the next available MRF server IP address configured in the list alternatively.
  • This process is repeated until S-SBC either receives a SUCCESS response from any of the MRF servers or all the MRF server IP addresses in list is exhausted.

Example: The MRF profile is configured with a list of MRF server IP addresses such as IP1, IP2, IP3 and IP4, then for the 1st call, S-SBC tries to connect for MRF server IP1. Meanwhile, S-SBC received 2nd, 3rd, 4th calls and connected to the MRF servers IP2, IP3 and IP4 respectively. For the 1st call, the S-SBC has received a Failure/No response from the MRF server IP1. Hence, the S-SBC tries with IP2 and connects successfully.

Signaling and Media Flow

Signaling and Media flow for a transcoded call using S-SBC, M-SBC and MRF:

  • S-SBC: Provides signaling services and responsible for allocating/activating/managing various resources (including MRF). Configures media flow through M-SBC and MRF.
  • M-SBC: Provides media services. Public interface is used to communicate with peers and private interface is used to communicate with MRF.
  • MRF: Provides transcoding services. Configured in private network of SBC and uses RFC-4117 interface to communicate with S-SBC.

 

Figure : Signaling and Media Flow