ISDN User Adaptation (IUA) In addition to addressing SS7 over IP, the SigTran group also addressed the backhaul of ISDN over an IP network. RFC 3057 [142] defined the IUA, which is supplemented | ISDN User Adaptation IUA In addition to addressing SS7 over IP the SigTran group also addressed the backhaul of ISDN over an IP network. RFC 3057 142 defined the IUA which is supplemented by an Implementer s Guide 143 that seamlessly supports the user and QSIG . It also supports both ISDN Primary Rate Access PRA and Basic Rate Access BRA as well as Facility Associated Signaling FAS Non-Facility Associated Signaling NFAS and NFAS with backup D channel. Further extensions to IUA are defined for DPNSS DASS2 144 145 and GR 303 146 that will most likely become RFCs in the future. Figure 14-25 Early Cisco SS7 IP Solution Cisco was working on a SLT device before the SS7 IP IETF standardization efforts began. The Cisco SLT is a modular access router Cisco 2611 or 2651 that terminates SS7 signaling links and backhauls MTP Level 3 and above to a PGW 2200 formerly SC 2200 and VSC 3000 MGC. Figure 14-26 shows an example configuration of two Cisco SLTs providing SS7 termination and backhaul for the Cisco PGW 2200 Softswitch. Figure 14-26. Cisco SLT Example View full size image NOTE For additional information about Cisco Softswitch products including the PGW2200 and BTS10200 visit the following Web site http en US products sw voicesw . The SLT supports either SS7 A-link or F-link configurations. As noted previously some SS7 links are deployed with bearer channels that are provisioned on the time slots that are not used by signaling channels. The SLT supports a drop-and-insert feature which allows the signaling channels to be groomed from the facility. The bearer channels are hair pinnned on the interface card that is to be sent to a MG. Figure 14-27 shows an example of the drop-and-insert feature. Figure 14-27. Example of SLT Drop-and-Insert Feature View full size image Each 2611 SLT can terminate up to two SS7 links and the 2651 SLT can terminate up to four links. Both have support for ANSI ITU TTC and NTT variants. Several physical .
