An SBC or Session Border Controller is a powerful device that sits at a point of demarcation for SMB and Enterprise businesses. It provides services such as call control, security, interoperability and voice optimization. When used in a VoIP network it would hide your Topology, IP Addresses Translation,provide Encryption and Transcoding, and Classification.
When call is arrived at an SBC, the Ribbon Session Border Controller hides the sensitive information so no outside intruder can exploit this information to hack your enterprise VoIP Network and hides the topology of the network. It also translates the local IP addresses of the callers to the WAN IP address of the SBC and performs protocol normalization also providing encryption and transcoding thus making you VoIP network completely secure and efficient. You can have Microsoft Teams Direct Routing using a certified SBC like Ribbon or Oracle. You can deploy an SBC in different configurations for the ease of deployment and investment protection.
Ribbon Session Border Controllers have different network interfaces available. As a matter of fact, can have Analog lines, E1/T1, ISDN, BRI or a SIP trunk. When you have PSTN connectivity directly connected to an SBC it is called an upstream deployment. When the SBC is connected with a PBX and that PBX is connected to PSTN then it is downstream configuration. SBC indeed can have a number of different advantages in an enterprise to provide secure and reliable voice or video communications.