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In this section:
The Lawful Interception solution has three discrete interfaces between the network element and mediation server to provide provisioning, call data (signaling) and call content (media) information. These interfaces are created after the connection is established between the XCIPIO mediation server Delivery Function (DF) and the network element Access Function (AF). The interface from the mediation server to the lawful interception agency is standardized. The interfaces between AF and DF are defined as:
where the X interface is defined by the 3GPP standard while INI is defined by the ETSi standard.
An interconnect SBC provides peering between IMS network and other peering networks (CDMA, business, and other service providers). The SBC interfaces with two XCIPIO mediation servers. The Network elements expose provisioning, call data and/or call content interface towards these mediation servers for legal interception.
The Mediation Function (MF) provides the required interworking by interfacing to the Law Enforcement Agency (LEA) through Handover Interfaces (HI1, HI2, HI3) on one side and to the VoIP packet network elements(s) through X3 (for collection of media).
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The Sonus EMS acts as a AF (Administrative Function) from an SS8 mediation function perspective to terminate provisioning of the targets.
The Sonus SBC acts as CC IAPs (call content IAPs) for bearer interception.
The Sonus LI solution supports the interfaces with the SS8 mediation function to facilitate X1 provisioning and X3 media information for the target.
The Sonus LI solution supports X1 and X3 interfaces only. X2 interface is not supported for this feature.
The Lawful Interception (LI) architecture supported by Sonus network elements (EMS, PSX, S-SBC and M-SBC) with SS8 as the mediation server is depicted below.
The X1 interface enables CALEA Intercept Access Points (IAP) to support multiple (two instances) regionally deployed SS8 Delivery Function systems to provision intercept targets. The EMS supports X1 interface over Transport Layer Security (TLS) connection towards the mediation server.
Configure the intercept server X1 transport address and TLS certificate from the EMS to initiate a transport connection over the X1 interface. The transport address and TLS certificate are individually specified for each of the mediation servers in the network.
The TLS configuration on the X1 interface is optional.
The SS8 Intercept server provisions the target URIs (SIP/SIPS or TEL URI) over the X1 interface on the EMS. EMS sends the target information to the Master PSX over the PIPE interface established over a SSH connection. The PSX Master and Slave store the targets in a LI Target table.
The Sonus SBC supports X3 interface to intercept call content towards the mediation servers over TCP/IPsec.
IPsec for X3 interface is optional.
The X3 interface is configured on the SBC under call data channel.
Call Data Channel (CDC) is required to be configured on both S-SBC and M-SBC.
The PCSI intercept call flow is listed below:
The M-SBC validates X3 transport address against the mediation servers configured under CDC and intercepts the call content to the corresponding mediation server using the X3 interface.