SBC For Lawful Interception

Overview

acting as P-CSCF or I-BCF can be configured to intercept IMS sessions. This feature can also be used in non-IMS deployments, to intercept audio/video/clearmode and fax streams.

The figure below depicts the deployment scenario of the 

to support Lawful Interception (LI).

 

• X1 interface: This interface is known as Provisioning interface that is supported by Sonus EMS using SOAP XML/TCP.
• X2 interface: This interface is known as Signaling interface that is supported by Sonus 
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  to send call data (signaling) messages over TCP using an optional IPSec tunnel. This interface encapsulates a copy of the SIP signaling message sent/received towards/from the target.
• X3 interface: This interface is known as Media interface that is supported by Sonus 
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  to send call content (media) messages over UDP only. These media streams (audio/video/image/clearmode) carries a copy of the stream sent/received towards/from the target.

At a high level, the functions performed by the Lawful Intercept are:

• Support of Encapsulation mode (multimedia) for all signaling messages and media streams, Encapsulation mode signifies intercepting the received or sent signaling or media stream, by appending an header with extra information, towards the Mediation Server.
• Support for SIP URI and DN based interception
• Support for intercepting RTP media types such as audio, video, image (fax), clearmode
• Support for intercepting any SIP signaling messages

• Support for sending intercepted signaling messages over TCP, using an optional IPSec tunnel

• Support for Real Time Control Protocol (RTCP)
• Support for Video and auxiliary video
• Support for Message Session Relay Protocol (MSRP) and Binary Floor Control Protocol (BFCP)
• Support for Far End Camera Control (FECC)

Call Data Channel (CDC) Model

supports various flavors of LI and a generic Call Data Channel (CDC) model to support any new flavors of LI. The new CDC configuration model is described as follows:

• The field priIpAddress was used to configure mediation server for IMS LI. The field mediaTypeIntercepted was updated with the value "multimedia" to distinguish IMS LI from the Legacy LI.
• The new CDC model co-exists with the old CDC model. The old CDC model is used only to configure default/legacy LI.
• The new CDC model have introduced two new fields vendorId and interceptStandard to identify and configure the flavors of the LI.
• Each Mediation Server can be configured to support both signaling and media interception. Separate configuration fields are present under the Mediation Server to handle this functionality.
• The new CDC model for a given mediation server allows media interception over UDP and/or TCP.
• The new CDC model for a given mediation server supports signaling interception either over TCP or UDP. It does not support both simultaneously.

If media interception over UDP and TCP both are configured at the CDC, the transport type for interception is decided based on the following conditions:

• For Audio, Video, and FECC interception:
      a. First preference is provided to UDP interception. If a CDC configuration for the Mediation server for media contains UDP mediation server information, media is intercepted over UDP.
      b. The next preference is provided to TCP interception. If a CDC does not have UDP Mediation server configuration and it has only TCP mediation server configuration for Media, media is intercepted over TCP.
• For MSRP interception:
     a. Only interception over TCP is supported.
     b. If CDC is not configured for TCP interception, interception is not supported.
• For BFCP over TCP:
     a. Only interception over TCP is supported.
     b. If CDC is not configured for TCP interception, interception is not supported.
• For BFCP over UDP:
     a. Only interception over UDP is supported.
     b. If CDC is not configured for UDP interception, interception is not supported.

The following table describes the configuration information required to distinguish between SS8 LI, IMS LI, and Default LI.

 

EMS/PSX support for LI

For more information on EMS and PSX configuration for Lawful intercept, see Sonus Lawful Intercept.

For configuration details, see Configuring SBC For Lawful Interception.