VoIP service providers have class 4 and class 5softswitchesas the backbone of their business. The class 5 Softswitch works at the retail end and lets users with IP-enabled phones, calling cards, or mobile devices make use of VoIP services. Class 4 Softswitch is primarily used by bulk telecom carriers for exchange to exchange connections. Both have some common features and one of them is least-cost routing or intelligent call routing. This feature can make quite a difference to the profitability of a VoIP service provider and to the telecom costs of their customers.