cuss two trunking solutions that are alternatives to SIP trunks: H.323 trunking: Transitioning H.323 trunks to SIP trunks is normally completed to provide enhanced features not available with H.323 and to ensure that the UC signal- ing protocols used throughout an organization are consistent. The issues with transi- tioning H.323 trunks to SIP trunks can be considered throughout this chapter; how- ever, most of the focus is on the transition of TDM trunking. TDM trunking: TDM trunking from an application to the PSTN is the method that is most widely used by enterprises, commercial, and Small and Medium Businesses (SMB) today and is the focus of most of the discussions in this chapter on the transi- tion to SIP trunks. As of the publication date in early 2010 in the United States, more than 90 percent of all PSTN access from companies is accomplished via TDM trunks provided by a service provider (SP). When transitioning from TDM to SIP trunks, it is best to break the overall process into steps. During each step, different information needs to be gathered, different groups need to be included, and different challenges need to be overcome. Depending on the needs and circumstances, each company follows a different set of steps. The variability of this process can be in both the order and methods for accomplishing each step. However, all companies need to address certain issues, which are discussed in the following sections. The phases of transition follow: Step 1. Assess the current state of trunking. Step 2. Determine the priority of a trunk transition project. Step 3. Gather information from SPs: The SIP trunk request for proposal process. Step 4. Conduct a pilot implementation of SIP trunks for PSTN access. Step 5. Transition a live department to SIP trunks for PSTN access. Step 6. Transition to SIP trunking at call centers. Step 7. Transition to SIP trunking at headquarters locations. Step 8. Transition to SIP trunking at branch locations. Step 9. Transition any other remaining trunking to SIP trunking. Step 10. 