Complete a post project assessment. As noted, not all companies need to complete all these steps, and the steps might occur in a different order, but following a distinct process for transition with distinct phases can Chapter 3: Transitioning to SIP Trunks 33 result in a transition that occurs faster and with fewer issues when compared to an unplanned transition from TDM to SIP trunks. Phase I: Assess the Current State of Trunking Before transitioning into a new method of interconnecting applications or interconnecting to the PSTN, the company needs to do a complete analysis of the PSTN connections and the connections between applications that currently exist. Companies often have many different points of interconnection to the PSTN or points of interconnection between applications that have developed over years and are not always recorded in a consistent manner. There might be cases in which two applications are actually connected via the PSTN, and a company is often paying for both incoming PSTN trunks into an application and outgoing trunks from another application that are connected. A complete audit of the TDM PSTN access to determine the physical location, size, and cost of trunking is an essential first step to determine the state of trunking at the company. This assessment should be conducted from both a technology infrastructure and SP billing point of view. From a technology infrastructure point of view, gathering a complete list of equipment and applications that utilize trunking needs to be undertaken. For most large and well- used applications, such as PBX interconnection to the PSTN, this list is easy to determine; however, several applications, such as postal meters, alarm monitoring systems, or paging systems might utilize trunking that is not obvious but is essential for gathering an accu- rate assessment of trunking requirements. The assessment from a billing point of view is important to ensure that no trunks are paid for by the company that are not needed, understood, or controlled by the cen