The SBC Core acting as IBCF (Interconnect Border Control Function) is positioned at the IMS edge and interconnects the operator to other IMS and fixed networks. See SBC as IBCF figure below.

Figure 1: SBC as IBCF

The SBC becomes involved in the SIP signaling path under the following conditions:

  • When the User Equipment (UE) roams to other IMS networks and P-CSCF is located in the Visited Public Land Mobile Network (VPLMN), the SBC as an I-BCF (exit point of the network) connects to the home network of the subscriber.
  • As an entry and exit point to the IP Multimedia Core Network (IMCN) when SIP messagiing is routed between two different IMS operators or IMCN networks.

At a high level, the functions performed by the IBCF are as follows:

  • Network configuration or Topology hiding
  • Application level gateway
  • Transport plane control, i.e. QoS control
  • Screening of SIP signaling
  • Media transcoding control
  • Privacy protection

In IMS networks, the IBCF interfaces with the following other functional elements:

  1. P/I/S-CSCF over Mx interface (SIP)
  2. BGCF over Mx interface (SIP)
  3. IBCF of other IMS Network over Ici/Izi interface
Ribbon IBCF provides the BCF (Border Control Function) by implementing both IBCF (Interconnect Border Control Function) and TrGW (Transition Gateway) functionality.

For details of configuring the SBC as IBCF, refer to Configuring SBC as IBCF page.