 After the first live deployment, companies generally evaluate the rest of the transition to SIP trunking to determine if any material changes from the initial estimates completed in 38 SIP Trunking the RFP occur. A partial live implementation does not need to be active for an extended period before a company considers the transition of other live departments. End-to-end SIP Trunk Branches Deployment Headquarters Call Center Figure 3-1 Areas for Transitions to SIP Trunks In summary, the first live deployment is an essential step in the successful deployment of SIP trunking throughout a company. Phase VI: Transition to SIP Trunking for Call Center Locations Call centers are always important for an organization; however, they can be either the pri- mary role of the company (that is, the company is in business offering call center servic- es) or a support role (that is, the call center supports the company's other primary func- tion). Outbound promotion call centers that play a supporting role for a company, such as outbound call centers for sales leads generation, are often a good, low risk early target for transition to SIP trunking. Outbound call center solutions often have prerecorded announcements played before live operators are engaged, and because of the high num- ber of calls that need to occur, often a high trunking cost is associated with these types of locations. Furthermore, outbound calling is easier to transition than inbound call centers because there does not need to be any changes in the carrier network to indicate new routing of calls. The company initiates all calls and as such the risk for misrouting is low. Inbound call centers often have some type of toll free number (such as 1800 or 1888) that is routed to a physical location by mapping to a standard (for example, E.164) phone number. Because inbound call centers have a history of utilizing the SP to route calls to multiple locations, the additional of a SIP trunking solution to also route calls is easily accomplished. Carriers often offer a 