Microsoft Office Communications Server R2 Glossary of IT Terms Terms Active Directory (AD) Domain Services

The directory service that stores information about objects on a network and makes this information available to users and network administrators.

Active Directory Container

An Active Directory node that is the basic place-holder for information in Active Directory Domain Services. Active Directory Domain Services consists of a set of containers organized in a hierarchical structure.

Active Directory Domain

An Active Directory domain is a collection of computers defined by the administrator of a network that is based on the Microsoft Windows® operating system. These computers share a common domain name, directory database, security policies, and security relationships with other domains. An Active Directory domain provides access to the centralized user accounts and group accounts maintained by the domain administrator.

Active Directory Forest

A collection of one or more Windows domains that share a common schema, configuration, and global catalog, and are linked with two-way transitive trusts. A forest is the basic sphere of trust in Active Directory Domain Services. Some global enterprises choose to have a single Active Directory Forest, while others may choose or inherit multiple Forests.

Active Directory Forest Root Domain

In Active Directory Domain Services, the initial domain in an Active Directory forest.

Active Directory Functional Level

Indicates the range of acceptable versions of Windows Server for domain controllers within a domain or forest. Functional levels provide an enterprise with a phased upgrade path for its Active Directory infrastructure to later versions of Windows. For example, a domain that is at the "Windows 2000 Native Mode" functional level can support domain controllers that run Windows 2000, Windows Server 2003 or Windows Server 2008; a domain that is at the "Windows Server 2008 Mode" functional level can only support domain controllers that run Windows Server 2008. Office Communications Server 2007 R2 requires a domain and forest functional level of "Windows Server 2003" or higher.

Active Directory Global Catalog

A directory database that applications and clients can query to locate any object in a forest. The global catalog is hosted on one or more domain controllers in the forest. It contains a partial read only replica of every domain directory partition in the forest. These partial replicas include replicas of every object in the forest, as follows: The attributes most frequently used in search operations. The attributes required to locate a full replica of the object.

Active Directory Organizational Unit

An Active Directory container with user, computer, or other objects that are grouped together for administrative convenience. The grouping may correspond to organizational structure, geographical location, or other criteria.

Active Directory Preparation

The act of populating Active Directory Domain Services with containers, objects, and permissions required to operate Office Communications Server. This step is typically the first step of the OCS install sequence within an enterprise, and introduces forest-wide and domain-wide objects. This process only needs to be performed once, and is updated with the installation of new OCS versions in the enterprise.

Active Directory Replication

The process by which a change made anywhere within Active Directory Domain Services (for example, a new user account being added) propagates to all relevant copies (or replicas) of that information across the enterprise Active Directory Domain Services. This process is controlled by administrator defined replication schedules and is automatic.

Active Directory Site

A collection of well-connected Active Directory resources (computers, users) usually corresponding to a geographic location.

Active Directory tree

A set of Active Directory containers organized in a single hierarchy, starting with a single top-level enterprise domain and including all subdomains.


A person in a LiveMeeting conference that is not designated a Presenter and not the meeting Organizer. An attendee can watch, but not present, app-sharing or presentation content.

Call Flow

The entire sequence of protocol messages (requests and responses) that is required to enable an end-user scenario.

Central Forest

An approach for maintaining multiple Forests in an enterprise, involving designating a single existing Forest (often the one with the most user accounts) as the "Central Forest" and locating infrastructure servers such as Office Communications Server and Exchange in that forest. User accounts in other forests are replicated as contact objects in the Central Forest via Microsoft Identity Lifecycle Manager (ILM).


An encrypted file containing user or server identification information, which is used to verify identity and to establish a secure link

Certificate Server

A Microsoft server role used to obtain certificates for Office Communications Server. This is a key component of an enterprise Public Key Infrastructure (PKI), for internal security.


Having 3 or more people collaborate in real time, using some combination of Instant Messaging, Application or Document Sharing ("Web Conferencing"), IP Audio, Telephony, and/or Video.


A special trust added between Forests, to enable resources in one Forest to access resources in the other. By default, a Forest is a stand-alone unit of trust and does not trust other Forests; such a trust must be added through manual administrative means.

Direct SIP

An interoperability configuration between OCS and an IP PBX involving a direct IP connection between the OCS Mediation Server role and the IP PBX, using SIP as the communications protocol.

DNS SRV record

A mechanism within Domain Name Service (DNS) that allows contacting a specific service (e.g. Office Communications Server) in a domain without knowing a specific server name or address in advance. This is the mechanism by which Communicator clients can automatically identify an appropriate Office Communications Server to connect with for logon, based on the domain portion of the user's SIP address.

Domain Controller

The server role that provides Active Directory functionality. Each Active Directory domain must have one or more domain controllers. Domain Controllers store critical data in Active Directory Domain Services, such as the tree structure for the domain, user accounts, server accounts, and permissions, as well as information relevant to the entire Forest containing the domain.

Domain Name System (DNS)

A hierarchical, distributed database that contains mappings of DNS domain names to various types of data, such as IP addresses. DNS enables the location of computers and services by user-friendly names, and it also enables the discovery of other information stored in the database.

Dual Forking

A technology that enables IP-PBXs to share a common number within Office Communications Server 2007 to provide a richer user experience.

Enterprise Edition

The higher-end Office Communications Server edition. Enterprise Edition enables High Availability for Office Communications Server, by separating Front-End Servers from a Back-End Database, thereby enabling Load-Balancing for Front-End Servers.

Event Logs

The mechanism used by Windows to report system activity on a machine. Event logs are used for reporting, auditing, and troubleshooting purposes.

Exchange Hub Transport

The Exchange server role that performs routing functions for e-mail.

Exchange Unified Messaging

The Exchange server role that enables voicemail functions, and accessing voice functionality from Outlook.


A server or appliance used by an enterprise that separates its internal network from the Internet, for security purposes.

Group IM

Having 3 or more people participate in a single IM session. Also known as IM Conferencing.

Group Policy

The mechanism used by enterprises to centrally set administrative policies in Active Directory Domain Services, and have those policies propagate to desktop machines. Such policies can enforce security requirements or enable/disable application features.


The virtualization software introduced in Windows Server 2008. Hyper-V allows running multiple Windows virtual machines on a single computer.

In-band provisioning

The mechanism by which Office Communications Server transfers settings and policies to Office Communicator clients, as part of the logon process, using the SIP protocol.

Inbound Routing

The call routing processing performed by Office Communications Server when it receives a voice call request for a user. Inbound routing enforces user call forwarding settings on inbound calls, such as redirecting unanswered calls to a different number or to voicemail.

Internal User

An enterprise employee connecting into Office Communications Server from the enterprise's internal network.

Internet Security and Acceleration Server (ISA)

A Microsoft server product that provides firewall functionality.

IP Address

The main address used to identify a machine for network communications purposes, in a format defined by the Internet Protocol (IP). For the most common form of Internet Protocol (IPv4), an IP address consists of 4 digits, or "octets", separated by dots, with each octet representing a number between 0 and 255. For example, and are both IP addresses.


A standard protocol for secure authentication. The main authentication mechanism used in Active Directory Domain Services, and by Office Communications Server for authenticating users.

Live Communications Server 2005

The Microsoft product version prior to Office Communications Server 2007, offering Instant Messaging and point-to-point Audio/Video functionality, with High Availability.

Load Balancer

A server role or hardware appliance used to distribute client requests across available Server resources, for High Availability. A Hardware Load Balancer can be used to provide High Availability in Office Communications Server deployments, by distributing client requests across all the available Front-End OCS Servers in an OCS pool.

Location Profile

A set of phone number translation rules (normalization rules) that instructs Office Communications Server how to interpret phone numbers dialed by users from a specific geographical location. OCS uses these rules to translate a phone number dialed by a user from that location to a globally unique E.164 number, prior to routing the call.

Management Pack

A set of application-specific data used by Microsoft Systems Center Operations Manager to monitor a Server Application (e.g. OCS) deployment within an enterprise. A management pack includes a list of events and performance counters to monitor, a health model for the application, commands or scripts to invoke to address application health issues, monitoring views, and other aspects relevant to monitoring that application across a potentially large number of server and client machines.

Microsoft Management Console (MMC)

The User Interface used in Windows for most computer and server management operations. This user interface consists of a left-hand "scope pane", listing resources to be managed (such as instances of Office Communications Server or OCS pools), and a right-hand "results pane", listing properties about a specific entity selected in the scope pane (such as settings for a specific OCS server).

Microsoft Office Communicator Phone Edition

The version of Office Communicator that runs on high-end hardware phone devices.

Microsoft Operations Manager (MOM)

A family of Microsoft server software that provides event management, proactive monitoring and alerting, reporting, and trend analysis services.


The existence of multiple Active Directory forests within an enterprise. This can occur by design or (more commonly) through mergers & acquisitions.

Multiple Points of Presence (MPoP)

The ability for a user to log into Communicator through multiple endpoints simultaneously, such as from a work machine, a laptop, a cellphone (Communicator Mobile), a desk-phone, and a home machine. Each incoming call is forked to all endpoints, and the user can answer the call at any endpoint.

Multipoint Conferencing Unit (MCU)

The central entity that combines, or "mixes", the multiple media inputs in a conference and distributes the mixed media to each participant. For example, in an OCS Audio/Video conference, the OCS Audio/Video Conferencing Server acts as an MCU, taking as input one A/V stream from each participant, and producing one resultant output stream distributed to all participants.

Mutual Transport Layer Security (MTLS)

An authentication and encryption mechanism to secure both directions of a TCP connection using certificates from both endpoints. Used in OCS to authenticate and encrypt server to server connections, internally and on federated links.

Normalization Rule

A phone number translation rule that instructs Office Communications Server how to convert phone numbers dialed in a certain format by users from a specific geographical location to full E.164 numbers. For example, a normalization rule might instruct OCS to interpret any 5-digit number dialed by a user from New York and beginning with 3 to a number in the Seattle office, thereby converting a number like 30135 to +12065550135.

NT Lan Manager (NTLM)

A Microsoft protocol for authentication. NTLM was the main authentication mechanism used in previous versions of Windows prior to the introduction of Kerberos in Windows 2000, and still used where access to Active Directory Domain Services is not feasible (e.g. for remote users in OCS).

OCS Logger

An Office Communications Server tool for capturing protocol traffic and other events at the Server. OCSLogger is used extensively for server-side troubleshooting.

Open Federation

A form of federation that allows an enterprise to automatically federate with any other enterprise without any administrative intervention required on its part.


The person who schedules a conference or initiates an ad-hoc conference. The organizer is always a presenter.

Outbound Routing

The call routing processing performed by Office Communications Server after it has received a voice call request from Communicator and identified it as an outbound telephony call. Based on the destination number, outbound routing identifies an appropriate Mediation Server to connect through.

Outlook Voice Access

A feature that allows a Unified Messaging-enabled user to access their Microsoft Exchange Server mailbox over the telephone. Users can navigate through their mailboxes by using telephone-key or Speech input.

Perimeter Network

A dedicated network used to separate an enterprise's internal network from the Internet, for security reasons. A Perimeter Network contains firewalls and application-specific perimeter servers, such as OCS Edge Servers, that mediate traffic between the enterprise and the Internet.

Phone Usage

Indicates user authorization for a particular type of phone call. Usually corresponds to a telephony class of service, such as local, long-distance, etc. A voice policy consists of a set of usages.


A number between 0 and 65535 assigned to a user session or server application in an IP network. A port identifies a specific channel used on a machine for communication. The combination of a machine's IP address and port represents a unique address for an application to connect from or to.


Microsoft's next-generation enhanced command line interface in Windows. Powershell provides advanced capabilities such as scripting, objects, reporting, etc. to make command-line capabilities significantly more powerful in supported products such as Windows Server and Exchange.


A person in a LiveMeeting conference that can present app-sharing or presentation content, effectively having control of the LiveMeeting session. This person is either the organizer or is promoted by the organizer or another presenter.

Redundant Array of Independent Disks (RAID)

A disk storage technology that makes hard disk solutions more resilient to hardware failures. In a RAID configuration, part of the physical storage capacity contains redundant information about data stored on the hard disks. The redundant information is either parity information (in the case of a RAID-5 volume) or a complete, separate copy of the data (in the case of a mirrored RAID1 or striped and mirrored RAID 0+1 volume). The redundant information enables data regeneration. Using RAID increases the fault tolerance of an Office Communications Server deployment.

Remote Desktop Protocol (RDP)

The Microsoft protocol used for remotely accessing Windows computers and remotely performing GUI operations on those computers. RDP is used for desktop sharing in OCS 2007 R2.

Resource Forest

A forest dedicated to deploying server infrastructure (e.g. Exchange, OCS) within an enterprise. User accounts are typically retained in separate Active Directory forests to maintain a clear separation between user infrastructure and server infrastructure. Forest trusts are established to provide user account resource access to the forests where user accounts reside.

Resource Kit

1. A package of add-on tools for Office Communications Server, available for download from Microsoft. These tools span a broad variety of administrative tasks. 2. The definitive reference book for Office Communications Server, published by Microsoft Press.

Reverse Number Lookup

The process, for incoming phone calls, by which Office Communications Server looks up a target phone number in its directory to determine whether it represents a user enabled for OCS enterprise voice, and if so, translates to the phone number to the user's SIP address.


A record in Office Communications Server that determines how to route calls made to a specified phone number range by determining the next-hop mediation servers to route to.

Route Helper

An add-on tool for Office Communications Server, available from Microsoft, that provides administrators with an enterprise-wide view of OCS routes and provides "what-if" diagnostics to assist in route specification and troubleshooting.


1. For voice calls, the process of determining where to connect the call, based on criteria such as destination phone number, location, cost, bandwidth, etc. 2. For TCP/IP networks, the algorithms and processes that determine how packets get sent from a source IP address to a destination IP address, implemented at endpoints as well as intermediate entities in the network such as routers. These determine the "next hop" to send the packet to, at every network link.


A unique address for all real-time SIP-based communications for a particular user. SIP URIs have a form analogous to e-mail addresses, for example


An Office Communications Server add-on troubleshooting tool, used for OCS Servers or at clients. Snooper can visualize, search, and inspect call flow traces, particularly for SIP traffic.

Standard Edition

A server in the internal network running Office Communications Server 2007, Standard Edition that hosts all necessary services, including IM, presence, and conferencing services, as well as the database, on a single server.


The process of converting a user-dialed phone number string to an E.164 number, by Office Communications Server. OCS routes calls after performing the translation step.

Transmission Control Protocol (TCP)

The TCP component of TCP/IP that specifies mechanisms for reliable, bidirectional, end-to-end transmission of data streams between two machines.

Transmission Control Protocol/Internet Protocol (TCP/IP)

The fundamental network protocol that powers the Internet. TCP/IP defines mechanisms for segmenting data into packets, and then addressing, sequencing, transmitting, and routing such packets over the network from a source machine to a destination machine via intermediate routers. All network communication in OCS occurs over TCP/IP.

Universal Datagram Protocol (UDP)

A TCP/IP component protocol mechanism for segmenting, transmitting, and routing packets from a source machine to a destination machine. UDP does not have built-in reliability/retransmission mechanisms and is uni-directional, but is stateless, has low latency & hence is very efficient. It is therefore commonly used for transporting audio and video streams. TCP is built on UDP and adds bi-directionality and reliability mechanisms.

Validation Wizard

A tool built into OCS that provides initial testing of an OCS installation right after initial setup steps are completed. The Validation Wizard often points out critical missing steps and information relevant for first-time troubleshooting in a new installation, and can also be used at any time to validate basic system operation.

Virtual Server

The virtualization software introduced in Windows Server 2003. Virtual Server allows running multiple Windows virtual machines on the same computer.

Voice Policy

Determines the types of phone calls a particular user is authorized to make. Administrators segment their voice users into a number of classes (e.g. interns, managers, executives) and assign a Voice Policy to each class, that specifies what types of calls (emergency-only, local, long-distance, international, etc.) the class of users is authorized to make. A policy consists of a set of Phone Usages.

Web Conferencing

Having people remotely collaborate using Application Sharing or Document Sharing, usually in conjunction with a voice conference using some combination of IP Audio and telephony.

Windows Management Instrumentation (WMI)

A Windows technology used to maintain, read, and write settings for Windows applications. OCS uses WMI as a common framework for accessing and maintaining OCS server settings.