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21.6 THE BEARER INDEPENDENT CALL-CONTROL (BICC) PROTOCOLS 715Figure 21.6-6. BICC call setup example.where SN-A is the originating (preceding) SN and SN-B is the terminating (succeeding)SN. The example describes a link in an end-to-end connection and appliesequally to ISN–TSN, TSN–TSN, TSN–GSN, or GSN–GSN connections.The process starts (0) when the CSF in SN-A (CSF-A) receives an IAM message,which could be an ISUP IAM (for an ISN), or a BICC IAM (for other SN types).CSF-A selects a BIWF and then processes the IAM to determine the routing ofthe call. Once the route has been chosen (in this case CSF-B), CSF-A sends (1) aBICC IAM message to CSF-B with the media characteristics of its BIWF. CSF-Bprocesses the IAM and, if able to route the call, sends (2) an IAM to the nextnode. CSF-B then selects a BIWF that matches the media characteristics from thereceived IAM and (3) requests, and (4) receives from BCF-B (via the CBC protocol),the BCN-ID and the media characteristics of the bearer connection. CSF-Bsends (5) BIWF-B’s address, the BNC-ID, and the media characteristics toCSF-A in an APM message. CSF-A (6) forwards the binding information toBCF-A in a CBC protocol message. BCF-A then (7) requests, and (8) receivesfrom MMSF-A, the bearer interface address, via a BMC protocol. BCF-A (9)sends MMSF-A’s bearer address to BCF-B, who forwards it (10) to MMSF-B.MMSF-B sends (11) its own bearer address to BCF-B, from where (12) it is forwardedto BCF-A. BCF-A (13) forwards MMSF B’s bearer address to MMSF-A.