enterprise owns SBC, you might need to buy a separate soft- ware license depending on your traffic. A primary benefit of SIP trunks over PRIs is that SIP trunks can be purchased in incre- ments of 1, whereas PRIs need to be purchased in increments of 23 channels. Monthly Recurring Costs You should expect some monthly recurring costs for any telecom services, unless it is at a per usage basis. When you want to pay as you use, the cost of the service can be signifi- cantly higher. A common practice in the telecom industry is that it charges a certain amount of money to keep your service running, irrespective of your usage. The two types of recurring costs for SIP trunks are the port/line charge and the bandwidth charge. Port/Line Charge In general, in the United States, analog lines cost approximately $16 per month. A PRI costs between $450 to $650 depending upon the carrier. Table 4-1 shows the typical line charge. A SIP trunk costs between zero (you pay for only calls you make) to $25 per channel or port. In the industry, some large carriers charge even $50/port or concurrent calls. And, there is a high possibility that they include some free voice minutes with that port. Therefore, you might recognize substantial savings in monthly charges. Table 4-1 Port/Line Charges Service Amount Analog (FXO port) $16-$25/month PRI (T1) $450-$650/month SIP Trunk (per 0-$50 channel) 50 SIP Trunking Bandwidth Charge The bandwidth for voice communication is not significant when you compare it with your data bandwidth requirement. When you deploy SIP trunks, you need to increase network bandwidth everywhere. Following are the two areas where you might need to spend money to increase your bandwidth: Bandwidth between headquarters and the branch: When you bring all your branch voice calls to headquarters to terminate through SBCs, you need to increase your bandwidth at each branch location. Your branches might connect to headquarters through MPLS/VPN, SO you need to ask your MPLS service provider to increase the bandwidth as needed