ward end-to-end IP communications. IP telephony has traditionally been about connecting new IP endpoints, such as IP-PBXs from businesses or IP Phones for consumers to the tradi- tional time division multiplexing (TDM)-based PSTN. In the consumer world, the transi- tion from TDM to IP occurred at the handset using a device such as an Analog Telephony Adaptor (ATA) voice, which was converted from TDM signals into IP. In the business world, the traditional method was to have IP handsets and the conversion to TDM occur at the edge of the network. This enabled businesses to continue to purchase traditional TDM connectivity services. The latest trend is for the SPs to offer IP-based PSTN con- nectivity services or trunks. This enables traditional IP-PBX customers in both large and small business to purchase IP trunking services as opposed to traditional TDM trunking services. Approximately three-quarters of large companies in the United States have already made the switch to IP telephony, initially to the dismay of the traditional phone companies; although many of the traditional phone companies have transformed themselves into Tier-1 VoIP SPs. Companies who have made the switch from TDM to IP telephony have lowered their bandwidth costs, reduced personnel requirements, saved on taxes, and spent less on moving, adding, and changing phone lines. This chapter covers the trends in Enterprise Unified Communications, endpoints, and call centers. Major Trends in IP Communications IP communication has gone through many changes in the 15 years since the first VoIP solutions were created. However, even after 15 years of development, there is a bright future. The trends that occurred over those 15 years have been in several areas focused around creating a better and lower-cost alternative to the traditional phone. However, some of the overall themes of these trends have been consistent. Traditional telephony includes a fixed number of protocols, endpoints, and applications. SS7, ISDN, and CAS are the primary protocols; TDM base