3 channels) capac- ity to support the peak hour calls for each location. However, when it is the peak hour in location-1, you might have unused channels in location-2 and location-3. So, location-1 can use the capacity of other locations when needed. If you combine the channel capaci- ty for all the locations together, it will always be less than the sum of all the capacity at individual locations. This ensures you purchase fewer concurrent calls at each location and share resources to provide time-of-day benefits and peak usage management. It leverages a better trunk utilization that is not feasible with standard TDM lines with physically defined connections. Figure 4-1 explains the operation model of the burstable shared trunk concept. Three sites have a limited number of concurrent call capacity (for example 10 port/ location). Under this configuration, each site can have ten simultaneous calls including both incoming and outgoing calls. If Location-C receives more than ten calls in a certain period of time, the system refuses those calls even though unused trunks might be in other locations. If your service provider enables you to share the extra trunks from other locations, the extra calls will go through, saving you a lot of money. This is not possible in TDM network. Chapter 4: Cost Analysis Location A Concurrent Call Ports 10 Total Ports Concurrent Call Ports Represent Simultaneous Inbound and Outbound Location B Local and LD Calls or SIP Paths Concurrent Call Ports 10 Total Ports SIP Network Location C Gateway Concurrent Call Ports 10 Total Ports No Additional Calls Can Be Connected Figure 4-1 Burstable Shared SIP Trunk Cost of Spike Calls Some businesses might require additional trunk capacity for certain periods of time (for instance, before Christmas, New Year's Eve, Mother's Day, or a special sales campaign). is difficult and costly to increase the capacity of a location for a few weeks and then dismantle it again. Increasing capacity in SIP trunks is just increasing the bandwidth for that location a