The SVI_C4 is a class 4 softswitch that offers powerful signalling and routing capabilities. It supports protocols like SIP, H.323, and ISUP and can scale from 500 to 10,000 simultaneous calls. The softswitch also includes features like redundancy, billing integration, monitoring, and security. It can be deployed in various ways including as a protocol converter, by wholesale carriers, and for private SIP networks.