This document discusses session border controllers for small, medium, and large offices and enterprises. It presents the Sonus SBC 1000 and SBC 2000 models for small to medium offices that require up to 160 or 600 sessions respectively, with high availability and flexibility. The SBC 5110 and SBC 5210 models are designed for medium to large offices and enterprises needing higher session densities of up to 10,000 or 64,000 sessions respectively.