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Overview

The SBC Core supports ICE and DTLS with direct media and anti-trombone scenarios. Any call, which is setup as Direct Media call can become a non-Direct Media call due to call transfer or Re-INVITE. The SBC supports conversion of a Direct Media call to Non Direct media and vice versa and handles the ICE/DTLS interactions as per the following:

  • Direct media call between two devices that support ICE procedures and may use DTLS for media. The ICE procedures, connectivity checks, and DTLS procedures occur directly between the endpoints. The direct media works with early dialog (answer in 18x reliable) and/or 200 Ok. The SBCsends the following ICE and DTLS parameters are copied from Ingress SDP and sent in Egress SDP for direct media:
    • ICE parameters
      • ice-ufrag
      • ice-pwd
      • ice-lite
      • ice-mismatch
      • candidate
      • remote-candidates
      • ice-options
      • end-of-candidates
    • DTLS parameters
      • setup (active/passive)
      • fingerprint
  • ICE-Lite procedure for a call when it is reconfigured as non-direct media after setting up as a direct media call initially.

  • Reconfiguring a call to direct media with end to end ICE procedures after it is setup as non-direct media call using ICE-Lite procedures.

  • Transferring a non-direct media call that used ICE-Lite to a direct media call to another party by Refer mechanism.

Note

The SBC does not play any role in the ICE procedures for the transfer of a direct media call (that is connected through an AS) to a direct media call to another party except relaying the SDP parameters.

 

Inter-SBC Direct Media Scenarios

In inter-SBC direct media scenario, the call legs are on different SBCs.

The following diagram illustrates inter-SBC direct media scenario with end to end ICE and DTLS procedure.

Figure : The Inter-SBC Direct Media Scenario with End to End ICE and DTLS Procedure

 

Intra-SBC Direct Media Scenarios

In intra-SBC direct media scenario, both the call legs are on same SBC.

The following diagram illustrates intra-SBC direct media scenario with end to end ICE and DTLS procedure.

Figure : The Intra-SBC Direct Media Scenario with End to End ICE and DTLS Procedure

  • If both DTLS relay and Direct Media are configured on SBC, Direct Media takes precedence over DTLS relay.
  • A late media with pass-through call can be established as a Direct Media call if Direct Media configuration is enabled.
  • A late media with convert call can be established as a Direct Media call if Direct Media configuration is enabled. However, in this case the first INVITE sent by the SBC, the Egress side must have locally generated parameters (including local ICE candidates) in the SDP.

Anti-trombone Direct Media

Anti-trombone direct media uses normal direct media on the SBC facing the endpoints and anti-trombone configuration on the SBC side facing the SIP AS. This feature is useful when x-dmi cannot be passed through the SIP AS. For more information, refer to Media Antitrombone.

Figure : Anti-trombone Direct Media

ICE Ingress and Egress Compatibility

  • DTLS must be enabled on Ingress and Egress Trunk Groups if required for Direct Media.
  • ICE must be enabled and compatible between Ingress and Egress Trunk Groups for Direct Media ICE calls.

Table : ICE Ingress and Egress Compatibility

Ingress TG ICE ConfigurationEgress TG ICE Configuration


 NONEICE-LYNCICE-WRTCICE-Full
NONEYesNoNoNo
ICE-LYNCNoYesNoNo
ICE-WRTCNoNoYesYes
ICE-FULLNoNoYesYes

When a call is established as an ICE direct media call, the SBC does not support media handling. Therefore, the existing CDR fields are populated for Ingress and Egress local Ip address/ports as 255.255.255.255/65535 and Ingress and Egress remote IP address/ports as 127.0.0.0/5004 for each of the media streams on the call. For more information, refer to the section CDR Field Descriptions.

Call Flows

Inter-SBC Direct Media

Figure : Inter SBC Direct Media Call Flow

 

Intra-SBC Direct Media

Figure : Intra SBC Direct Media Call Flow

 

Anti-trombone Direct Media

Figure : Anti-trombone Direct Media Call Flow

SIP UA—IP Phone/PBX
SIP Server—PBX/Softswitch
Dialogx— Number of the dialog
IP—IP address in C line
SBCIP—IP address in Cline of the SBC

The MS Lync/Skype Remote Desktop Sharing feature is supported on all SBC Core platforms:

  • SBC 5000 series
  • SBC 7000
  • SWe (all environments)