Lync Server Terms and Acronyms
In the world of unified communications, there are many terms and acronyms that are routinely used that might be unfamiliar to those new to the Lync product line. This publication contains many references to these terms and acronyms; therefore, becoming familiar with the most common of these allows one to more quickly absorb the information in the remaining chapters. Following are some of the more common terms and acronyms that will be used throughout this publication:
• Call Admission Control (CAC)—A method of preventing oversubscription of VoIP networks. Unlike QoS tools, CAC is call-aware and acts as a preventive congestion control by attempting to route calls across other media before making a determination to block a call. Ultimately, the result of a properly implemented CAC configuration is that the quality of existing calls is preserved, even when bandwidth is scarce.
• Call detail records (CDR)—A record produced by a phone system containing details of calls that have passed through it. Each record includes information such as the number of the calling party, the number of the called party, the time of call initiation, the duration of the call, the route by which the call was routed, and any fault condition encountered. These records might be used for billing, for tracking of an employee’s usage of the system, or for monitoring system uptime and issues.
• Client Access License (CAL)—A software license that entitles a user to access specific systems or specific features in a system. A CAL is typically offered in two flavors: Standard and Enterprise.
• Common Intermediate Format (CIF)—A format used to standardize the vertical and horizontal resolutions in video signals, often in video conferencing systems.
• Direct Inward Dialing (DID)—A service offered by phone carriers wherein a block of telephone numbers is provided to a customer for connection to the customer’s internal phone system (including Lync Server or a traditional PBX). Incoming calls to the DID block are routed to internal destination numbers, which allows an organization to have significantly more internal lines than external lines.
• Dual-Tone Multi-Frequency (DTMF)—A method for providing telecommunication signaling over analog telephones lines in the voice frequency band. DTMF is also referred to as touch tone. This technology enables users to initiate events in the phone system by simply pressing a button on a keypad.
• Extensible Markup Language (XML)—A set of rules for encoding documents in a machine-readable format. The goal of XML is to be a simple and open standard for representing arbitrary data structures, and it is most often used in web services.
• Extensible Messaging and Presence Protocol (XMPP)—An open, XML-based protocol designed to provide near-real-time extensible IM and Presence information. XMPP has more recently expanded into VoIP and file transfer signaling.
• Hardware Load Balancing (HLB)—A method of distributing a workload across multiple computers to optimize resource utilization, increase throughput, and provide a level of redundancy through the use of an external hardware device.
• Instant messaging (IM)—A form of real-time, direct, text-based communication between multiple parties. IM is sometimes referred to as online chat.
• Interactive Voice Response (IVR)—A technology that enables a system to detect voice and dual-tone multifrequency inputs. IVR is often used in telecommunications as an input for automated decision trees. For example, IVR technology is used behind the scenes with voice menu prompts that are frequently heard, such as “press 1 for English.”
• Mean Opinion Score (MOS)—In multimedia, MOS provides a numerical indication of the perceived quality of a call after compression and/or transmissions. MOS is expressed as a single number ranging from 1 to 5, with 1 being the lowest perceived audio quality and 5 being the highest perceived audio quality.
• Network Address Translation (NAT)—A method of modifying network address information when packets pass through a traffic routing device. NAT effectively remaps a packet from one IP space to another, and is common in home usage when there are multiple computers with a private IP addressing site behind a router or firewall that holds a publicly routable address. NAT maps a port back to the initiating internal host and reroutes responses back to the originating host.
• Network Load Balancing (NLB)—A method of distributing a workload across multiple computers to optimize resource utilization, increase throughput, and provide a level of redundancy through the use of software running in the Windows operating system.
• Plain Old Telephone Service (POTS)—Another term for PSTN.
• Public Switched Telephone Network (PSTN)—The global network consisting of the world’s public circuit-switched telephone systems. The first company to provide PSTN services was Bell Telephone.
• Private Branch Exchange (PBX)—A telephone system that serves a particular business or office as opposed to a common carrier or a system for the general public. A PBX is what traditionally provides voice services to companies that are connected to a local exchange, and provides external connectivity to the PSTN for users in that organization.
• Quality of Experience (QoE)—A subjective measure of a customer’s experiences with a vendor or service.
• Quality of Service (QoS)—A mechanism to control resource reservation in a system; typically, it is a method to prioritize various traffic types to ensure a minimum level of performance for a particular type of traffic.
• Realtime Transport Protocol (RTP)—A standardized format for delivering audio and video over the Internet. A noted advantage of RTP is its ability to handle large amounts of packet loss before the impact on the call becomes noticeable.
• Remote Call Control (RCC)—A method of utilizing a phone resource on one system with a resource on another. Typically, in the context of Lync Server, this is the capability to use a Lync client to place a call through a desk phone that is controlled by a PBX rather than by Lync Server.
• Role-based access control (RBAC)—An approach to restricting system access to authorized users by granting the rights based on the role served by the user. This normally results in granular permissions with the goal of granting the minimum level of rights needed to perform a task.
• Session Initiation Protocol (SIP)—An Internet Engineering Task Force (IETF) defined protocol used for controlling multimedia communications sessions. The goal of SIP is to provide a common signaling and call setup protocol for IP-based communications.
• SIP for Instant Messaging and Presence Leveraging Extensions (SIMPLE)—An open standard protocol suite that provides for the registration of Presence information and the receipt of Presence status notifications.
• Survivable Branch Appliance (SBA)—A physical appliance that combines the Lync Registrar, Mediation Server, and PSTN gateway services in one compact unit; it is designed to maintain most voice services for a branch site that has lost connectivity to the main Lync Server site.
• Transmission Control Protocol (TCP)—One of the core protocols of the Internet, TCP is a protocol that provides reliable ordered delivery of a stream of packets from one device to another. TCP has the advantage of sending an acknowledgment of receipt of a packet back to the sender, resulting in increased reliability. This acknowledgment, however, comes at a performance price and can therefore serve to limit the scalability of TCP.
• Uniform Resource Identifier (URI)—A string of characters used to identify a name or a resource on the Internet. This allows interaction with representations of the resource over a network, often the Internet, using various protocols.
• User Datagram Protocol (UDP)—Another one of the core protocols of the Internet, UDP delivers a stream of packets from one device to another, but does not attempt to order or verify delivery of packets. UDP also does not need to first initiate a conversation with a destination host via a handshake. This behavior makes it faster and more scalable than TCP, but ultimately it is less reliable.
• Virtual Private Network (VPN)—A method of passing packets across a public network in a secured and authenticated manner. VPNs enable users to access their private corporate networks through connections to the public Internet.
• Voice over IP (VoIP)—A generic term for transmission technologies that deliver voice communications over IP-based networks. VoIP is also referred to as IP Telephony or Internet Telephony.