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In this section:

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Related articles:

EMA:

CLI:

Overview

Audio Transcoding and Video Relay

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MultiExcerptNameInvoke MRF Intro

The 

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

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Only the

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on OpenStack (D-SBC) supports this feature. 


The
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 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
  • Audio and T.140 transcode through MRF (see T.140 and TTY Interworking Support below)
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The

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

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If the Packet Service Profile is configured as "transcode-only", the

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transcodes the audio and relays video/ T140.

T.140 and TTY Interworking Support

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MultiExcerptNameT140 Support

Prior to release 7.1.0, the

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invoked MRF only for audio streams to achieve transcoding. Non-audio streams were relayed end-to-end even when the audio was sent to the MRF. Teletype (TTY) as the legacy service offered through encoding text characters as tones that are embedded in a carrier (PCMU, PCMA, or EVRC) media stream. The T.140 streams carry text as a separate payload.

Henceforth, the

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invokes MRF for T.140 and TTY interworking to achieve transcoding. When T.140 and TTY interwork, text characters exchange between the T.140 stream and the tones carried inband with the audio. If the audio is pass-through and T.140 requires transcoding, the SBC does not invoke MRF and instead rejects the text stream on the offer leg (see the following call flow). Keep in mind that T.140 pass-through scenarios are supported without any MRF interaction.

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This feature does not support sessions that only have a T.140 stream.

The

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does not invoke T.140 and TTY interworking when T.140 is present on both legs and has different transmission rates, or a difference in redundancy packet support.

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Only the

Spacevars
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on OpenStack (D-SBC) supports this feature. 

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1Audio and T.140 Transcoded
3Audio and T.140 Transcoded

 

For T.140 and TTY interworking to succeed,

  • the offer received by the SBC must have a text stream with a valid IP and Port, and the answer received by the SBC must have a text stream with port=0,
  • the audio must be transcoded,

  • the audio codec on the TTY leg must be Baudot capable (G711U, G711A, or EVRC).

The existing t140Call flag in the PSP achieves T.140 and TTY interworking for MRF transcoding. The following table outlines when the T.140 and TTY can and cannot interwork.

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1PSP Configuration

Offer Leg Route

PSP (T.140 Call)

Answer Leg Route

PSP (T.140 Call)

 

Result

DisabledDisabledT.140 disabled on both legs
DisabledEnabledT.140 disabled on both legs
EnabledDisabledT.140-TTY can interwork
EnabledEnabledT.140-TTY can interwork

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A need for interworking is evident when an m=text line for the leg that sends T.140 is below the m=audio line for that leg, and when there is no m=text line for the other leg in the offer sent toward MRF.

If T.140 and TTY interworking is not required but audio transcoding is required, the audio streams go through MRF and the T.140 streams do not go through MRF.

If the audio is pass-through and T.140 requires transcoding, the SBC does not invoke MRF and instead rejects the text stream on the offer leg (see the following call flow).

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1Audio pass-through

Image Added

 

If T.140 and TTY interworking is required but MRF does not support interworking, the SBC rejects the T.140 stream on the leg that offers T.140.

SBC SWe Cloud Limitations

  • Audio-less calls are not supported.
  • Only video and T140 streams among the non-audio streams are supported.

For configuration details, refer to:

To view media stream statistics, refer to Show Status Address Context - Call Status Details

Prerequisites to Invoking MRF

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The first three activities below cause the D-SBC to include DSP when invoking invoke 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 
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    TextPacket Service Profile - CLI
    URLPacket Service Profile - CLI
    ).
  4. Create a Path Check Profile, ARS profile, and CAC profile during the initial configuration

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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.

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To configure the Domain Name of MRF Server, select FQDN:

Note

When FQDN routing is enabled, configure DnsGroup on zone in which mrfTgName is present. 

To configure an IP-Address for the MRF Server, select IpAddress.

Note

When Routing Type is selected as IP Address, a minimum of one IP must be configured. In case of multiple IP addresses, each IP address is separated by a comma (,).

Sonus supports a maximum of four IP address configurations.

To configure a dedicated TG on MRF servers:

To configure transport type for MRF server:

NoteDefault value is UDP.

To configure request URI sent in the invite towards the MRF server:

To configure Port of the MRF server in MRF Profile:

Note

When the mrfRoutingType is selected as IpAddress, mrfPort default value is 5060.

When the mrfRoutingType is selected as fqdn, mrfPort default value is 0. When the value for the port is 0, user must configure desired port in DNS server for SRV record.

To configure the state of the MRF server:

Configure Private LIF Groups in M-SBC

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

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To configure Private IP Interface Group that communicates towards MRF, execute the loadBalancingService set command:

 

To view the configured Private IP Interface Group Name, execute the loadBalancingService show command:


Debug Statistics Commands

The following CLI can be used to get the media statistics corresponding to private NIF resources for an MRF call.

 

Use the following CLI 'show' command to view the call statistics for an MRF call.

> show status global callDetailStatus

The callDetailStatus command contains the following new fields (with example output):

 

 

Use the following CLI 'show' command to view the call resource statistics for an MRF call.

show status global callResourceDetailStatus

Note

Value dresMrf indicates MRF is used for transcoding the call.

Parameter: resType
Value: dresMrf

     

 

Use the following CLI 'show' command to view the call media leg information for an MRF call.

 

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

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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.

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    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

The Call Admission Control (CAC) feaure creates and configures a profile that provides each registered SIP or static endpoint to have individual limits on the number of active calls and the call rates. For more information, refer to CAC Provisioning - SIP CAC Profile.

  • For End point CAC, create CAC profile and attach to the IP Peer.

  • For TG CAC, create CAC profile and attach to the MRF TG as configured in the cluster profile.

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    Endpoint CAC does not support FQDN.

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    Bandwidth CAC is not supported for both TG and Peer level.

 

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.

 

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1Signaling and Media Flow

 

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