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In this section:


The SBC provides the function of an integrated IBCF and IBGF in the IMS Network-Network Interface (NNI). Note that the  transparently handles both the control and the user plane in this context.

 sits at the IMS edge and interconnects the operator to other IMS and fixed networks. It gets involved in the SIP signaling path in following situations:

Background Information

Supported Interfaces

The following interfaces are supported:


Support Requirements

Sonus Compliance


Support Mx interface; SIP signaling between and CSCF



Support Mb interface; RTP media stream between the and MGW, RTCP media control, associated with a particular RTP stream.

Partially compliant. Sonus' solution supports RTCP and RTP media stream between the and MGW.

User plane Traffic

Support UDP/TCP and RTCP


Gm (A-)

Supports SIP signaling between UE and P-CSCF (except for SIP signaling compression).


If-1 (A-)

CSCF interact with ENUM/DNS for translation of E-164 numbers into routable SIP addresses.

Not compliant


Support Mw interface; P-CSCF interacts with I/S-CSCF via SIP-signalling shall be supported according to 3GPP TS 23.228 (Stage 2) and 3GPP TS 24.229 (Stage 3).

Partially compliant. Sonus supports Mw interface.


P-CSCF support of Rf interface as defined in 3GPP TS32.260, with respect to the content of CDR. Vendor support of Diameter on this interface.



The Rx interface supports the QoS resource reservation for reserving bandwidth in the IP access network. The Rx reference point is used to exchange application level session information between the Policy and Charging Rules Function (PCRF) and the P-CSCF. The SBC, acting as P-CSCF creates a TCP connection with the configured PCRFs



The /IBCF is deployed at network boundaries, NNI and acts as a SIP B2B UA.