e the basic connectivity and power for end devices. Ethernet switches that are badly implemented with loops or that have a great deal of congestion can negatively affect IP Telephony deployments, including the quality PSTN access via a SIP Trunk. Non-IP Phone IP Telephony Devices Non-IP Phone IP Telephony devices usually include video. The two basic types of video endpoints are Standard Definition (SD) Video endpoints and High Definition (HD) Video endpoints. A subset of HD video endpoints include Telepresence video endpoints. As a component of IP Telephony, these endpoints normally share the dialplan of other IP Telephony devices, meaning that they can be accessed with a phone number and normal- ly share the bandwidth when calls are made between sites. When considering a SIP Trunk solution, it is important to consider how non-IP Phone devices will be able to consume the SIP Trunk services that are provided. WAN Connectivity Device All IP Telephony solutions that connect across long distances must have some type of WAN connectivity solution. The most standard types follow Metro Ethernet WiMax Cable (for example, DOCSIS) Chapter 1: Overview of IP Telephony For each of these connectivity solutions, a physical device sits on the customer's premis- es and connects to the service provider (SP). These SPs, in turn, connect to other SPs, ultimately forming a mesh that enables all SPs that use PSTN routing technology- specifically, the E.164 phone number-to communicate with each other. The size and capabilities of an enterprises' connection method with their SP determine which type of SIP Trunk solutions are possible. The bandwidth provided by the SP has two important components. First is raw bandwidth. This is an important measure of the number of packets per second and the size of the packets that can be sent from the enter- prise to the SP. The bandwidth provided by the SP is the ultimate determination of the number of simultaneous conversations that occur between the SP and enterprise and the number calls and size of