The Proxy-CSCF is an edge access function and is the entry point for a UE to request services from an IMS network. This CSCF acts as a proxy by accepting incoming requests and forwarding them to the entity that can service them. Examples of requests include registration and invitation for a multimedia session. ng-voice’s P-CSCF consists of the control component, the media handling component, and session storage components – following a truly cloud-native and microservices approach.

Main Features of ng-voice’s P-CSCF:

• Signaling firewall and user identity assertion (P-Preferred-Identity and P-Asserted-Identity header support)
• Integrity protection and optional encryption based on IPsec
• Rx interface towards the PCRF to ensure QoS on the mobile network and achieve the highest quality for voice and video calls
• Transcoding of the following codecs:
  • G711a/u
  • G722
  • AMR
  • AMR-WB
  • and various others
• Lawful intercept interfaces: X1, X2, and X3
• It is fully compliant with 3GPP release 15 and implemented according to 3GPP TS 29.214 and 3GPP TS 24.229

The I-CSCF determines which S-CSCF should be assigned for handling the session requested by the UE. The I-CSCF determines the most suitable serving S-CSCF by inspecting the UE capabilities as well as the capabilities of the available S-CSCFs.

The ng-voice I-CSCF is optimized for speed and minimalist state information is kept in it.

The I-CSCF is compliant with 3GPP release 15 and implemented following the 3GPP Specs TS 29.228, 3GPP TS 29.229 and TS 24.229.

The S-CSCF is responsible for conducting both session control and registration. It is responsible for maintaining the state of sessions and registrations and will trigger applications either provided by ng-voice or by a third party based on the service-profile provided by the HSS and using a 3GPP compliant ISC interface.

ng-voice’s S-CSCF consists of the control component and session storage components – following a truly cloud-native and microservices approach.

The S-CSCF is compliant with 3GPP release 15 and implemented following the 3GPP Specs TS 29.228, 3GPP TS 29.229, 3GPP TS 24.229 and 3GPP TS 32.229.

The E-CSCF is responsible for retrieving the user-location and locating the closest public safety answering point (PSAP, e.g. policy, fire-brigade or ambulance) for a subscriber.

The E-CSCF is compliant to 3GPP release 15. Applicable standards include EENA NG112 and NENA.

The ng-voice BGCF acts as a Gateway between the IMS and other networks. It allows manipulation of the signaling to meet requirements either on the IMS or on the outbound Gateway in order to simplify Interworking between networks.

Main Features of ng-voice’s BGCF:

• Outbound routing based on source-number and destination-prefix
• Caller-ID and R-URI manipulation for out- and inbound calls
• Authentication for outbound calls

The BGCF is compliant to 3GPP release 15. Applicable standards include 3GPP TS 24.229.

The ENUM server maps the telephone number of the destination into an URI (Uniform Resource Identifier). The URI is a SIP phone number that identifies the destination network. The ENUM server provides an API for provisioning and an option for bulk uploading provisioning entries. It can provide support for Number portability based on RFC 4694.

The ENUM is compliant to 3GPP release 15.