products. Because IP telephones plug into switches, and IP telephones require Quality of Service (QoS) enabled partly by switches, customers had confidence that the switches and tele- phones could be made to work together for the QoS levels needed for voice. Prior to Avaya's acquisition of Nortel, Cisco was the leading manufacturer of new IP systems, based upon number of systems sold. Microsoft is another example of an organization that took advantage of its data offerings and reputation by introducing a Voice over Internet Protocol (VoIP) service. Microsoft's VoIP product, Lync, integrates with its Outlook desktop software. Outlook manages e-mail, address book, and calendar applications SO that users can access all of them from a single desktop application. If a user has Lync, she will see telephone icons in Outlook for making, receiving, and managing calls. Data Centers and IP Private Branch Exchanges Manufacturers of IP-based telephone systems include the following: Aastra Alcatel-Lucent Avaya Communications Cisco Systems, Inc. Microsoft Mitel Networks Polycom ShoreTel, Inc. Siemens ICN Vertical Direct and Indirect Channels and Managed Services Most office telephone systems are sold through distributors and value-added resellers, not by manufacturers directly. However, there are manufacturers that use both direct and indirect sales channels. These manufacturers often have sales personnel that sell directly to large universities and multinational organizations. Distributors are used as an indirect channel for their smaller customers. Distributors include carriers and value- added resellers who, in addition to IP Private Branch Exchanges (PBXs), offer prod- ucts and services such as data equipment, consulting on data networks, and managed services. Managed services include maintenance and consulting on IP telephone sys- tems and peripherals, Wi-Fi wireless networking equipment, and data networks. Some distributors also act as agents for telephone companies. They place orders for data and voice services with carr