A

AD - Active Directory

is a technology created by Microsoft that provides a variety of network services, including:

• LDAP-like Directory services
• Kerberos based authentication
• DNS based naming and other network information

Using the same database, for use primarily in Windows environments, Active Directory also allows administrators to assign policies, deploy software, and apply critical updates to an organization. Active Directory stores information and settings in a central database. Active Directory networks can vary from a small installation with a few hundred objects, to a large installation with millions of objects.

Active Directory was previewed in 1996, released first with Windows 2000 Server edition, and revised to extend functionality and improve administration in Windows Server 2003. Additional improvements were made in both Windows Server 2003 R2 and Windows Server 2008. Active Directory was called NTDS (NT Directory Service

NT Directory Service

See Active Directory

) in older Microsoft documents. This name can still be seen in some AD binaries.

There is a common misconception that Active Directory provides software distribution. Software distribution is run by a separate service that uses additional proprietary schema attributes that work in conjunction with the LDAP protocol. Active Directory does not automate software distribution, but provides a mechanism by which other services can provide software distribution.

D

DC - Domain Controller

On Windows Server Systems, a domain controller (DC) is a server that responds to security authentication requests (logging in, checking permissions, etc.) within the Windows Server domain.

In Windows NT, one domain controller per domain was configured as the Primary Domain Controller (PDC); all other domain controllers were Backup Domain Controllers (BDC). A BDC could authenticate the users in a domain, but all updates to the domain (new users, changed passwords, group membership, etc) could only be made via the PDC, which would then propagate these changes to all BDCs in the domain. If the PDC was unavailable (or unable to communicate with the user requesting the change), the update would fail. If the PDC was permanently unavailable (e.g. if the machine failed), an existing BDC could be promoted to PDC. Because of the critical nature of the PDC, best practices dictated that the PDC should be dedicated solely to domain services, and not used for file/print/application services that could slow down or crash the system. Some network administrators took the additional step of having a dedicated BDC online for the express purpose of being available for promotion if the PDC failed.

Windows 2000 and later introduced Active Directory

Active Directory

is a technology created by Microsoft that provides a variety of network services, including:

• LDAP-like Directory services
• Kerberos based authentication
• DNS based naming and other network information

Using the same database, for use primarily in Windows environments, Active Directory also allows administrators to assign policies, deploy software, and apply critical updates to an organization. Active Directory stores information and settings in a central database. Active Directory networks can vary from a small installation with a few hundred objects, to a large installation with millions of objects.

Active Directory was previewed in 1996, released first with Windows 2000 Server edition, and revised to extend functionality and improve administration in Windows Server 2003. Additional improvements were made in both Windows Server 2003 R2 and Windows Server 2008. Active Directory was called NTDS (NT Directory Service

NT Directory Service

See Active Directory

) in older Microsoft documents. This name can still be seen in some AD binaries.

There is a common misconception that Active Directory provides software distribution. Software distribution is run by a separate service that uses additional proprietary schema attributes that work in conjunction with the LDAP protocol. Active Directory does not automate software distribution, but provides a mechanism by which other services can provide software distribution.

("AD"), which largely eliminated the concept of primary and backup domain controllers in favor of multi-master replication. However, there are still a number of roles that only one domain controller can perform, called the "Flexible Single Master Operation" roles (some of these roles must be filled by one DC per domain, while others only require one DC per AD forest). The AD forest is discussed in Active Directory Structure, under Objects Forests, Trees, and Domains. If the server performing one of these roles is lost the domain can still function, and if the server will not be available again until an administrator can designate an alternate DC to assume the role (a process known as "seizing" the role).

Datagram

In general, the term packet applies to any message formatted as a packet, while the term datagram is generally reserved for packets of an "unreliable" service. A "reliable" service is one that notifies the user if delivery fails, while an "unreliable" one does not notify the user if delivery fails. For example, IP provides an unreliable service. Together, TCP and IP provide a reliable service, whereas UDP and IP provide an unreliable one. All these protocols use packets, but UDP packets are generally called datagrams.

F

FTP - File Transfer Protocol

FTP or File Transfer Protocol is used to transfer data from one computer to another over the Internet, or through a network.

I

ISDN / ISDN 2 - Integrated Service Digital Network

Integrated Services Digital Network is a telephone system network. Prior to the ISDN, the phone system was viewed as a way to transport voice, with some special services available for data. The key feature of the ISDN is that it integrates speech and data on the same lines, adding features that were not available in the classic telephone system. There are several kinds of access interfaces to the ISDN defined: Basic Rate Interface (BRI), Primary Rate Interface (PRI) and Broadband-ISDN (B-ISDN).

ISDN is a circuit-switched telephone network system, that also provides access to packet switched networks, designed to allow digital transmission of voice and data over ordinary telephone copper wires, resulting in better voice quality than an analog phone. It offers circuit-switched connections (for either voice or data), and packet-switched connections (for data), in increments of 64 kbit/s. Another major market application is Internet access, where ISDN typically provides a maximum of 128 kbit/s in both upstream and downstream directions (which can be considered to be broadband speed, since it exceeds the narrowband speeds of standard analog 56k telephone lines). ISDN B-channels can be bonded to achieve a greater data rate, typically 3 or 4 BRIs (6 to 8 64 kbit/s channels) are bonded.

ISDN should not be mistaken for its use with a specific protocol, such as Q.931 whereby ISDN is employed as the network, data-link and physical layers in the context of the OSI model. In a broad sense ISDN can be considered a suite of digital services existing on layers 1, 2, and 3 of the OSI model. ISDN is designed to provide access to voice and data services simultaneously.

However, common use has reduced ISDN to be limited to Q.931 and related protocols, which are a set of protocols for establishing and breaking circuit switched connections, and for advanced call features for the user. They were introduced in 1986.

In a videoconference, ISDN provides simultaneous voice, video, and text transmission between individual desktop videoconferencing systems and group (room) videoconferencing systems.

IP - Internet Protocol

The Internet Protocol (IP) is a protocol used for communicating data across a packet-switched internetwork using the Internet Protocol Suite, also referred to as TCP/IP.

IP is the primary protocol in the Internet Layer of the Internet Protocol Suite and has the task of delivering distinguished protocol datagrams (packets) from the source host to the destination host solely based on their addresses. For this purpose the Internet Protocol defines addressing methods and structures for datagram encapsulation. The first major version of addressing structure, now referred to as Internet Protocol Version 4 (IPv4) is still the dominant protocol of the Internet, although the successor, Internet Protocol Version 6 (IPv6) is being deployed actively worldwide.

N

NTDS - NT Directory Service

See Active Directory

Active Directory

is a technology created by Microsoft that provides a variety of network services, including:

• LDAP-like Directory services
• Kerberos based authentication
• DNS based naming and other network information

Using the same database, for use primarily in Windows environments, Active Directory also allows administrators to assign policies, deploy software, and apply critical updates to an organization. Active Directory stores information and settings in a central database. Active Directory networks can vary from a small installation with a few hundred objects, to a large installation with millions of objects.

Active Directory was previewed in 1996, released first with Windows 2000 Server edition, and revised to extend functionality and improve administration in Windows Server 2003. Additional improvements were made in both Windows Server 2003 R2 and Windows Server 2008. Active Directory was called NTDS (NT Directory Service) in older Microsoft documents. This name can still be seen in some AD binaries.

There is a common misconception that Active Directory provides software distribution. Software distribution is run by a separate service that uses additional proprietary schema attributes that work in conjunction with the LDAP protocol. Active Directory does not automate software distribution, but provides a mechanism by which other services can provide software distribution.

T

TCP - Transmission Control Protocol

The Transmission Control Protocol (TCP) is one of the core protocols of the Internet Protocol

Internet Protocol

The Internet Protocol (IP) is a protocol used for communicating data across a packet-switched internetwork using the Internet Protocol Suite, also referred to as TCP/IP.

IP is the primary protocol in the Internet Layer of the Internet Protocol Suite and has the task of delivering distinguished protocol datagrams (packets) from the source host to the destination host solely based on their addresses. For this purpose the Internet Protocol defines addressing methods and structures for datagram encapsulation. The first major version of addressing structure, now referred to as Internet Protocol Version 4 (IPv4) is still the dominant protocol of the Internet, although the successor, Internet Protocol Version 6 (IPv6) is being deployed actively worldwide.

Suite. TCP is one of the two original components of the suite (the other being Internet Protocol, or IP), so the entire suite is commonly referred to as TCP/IP. Whereas IP handles lower-level transmissions from computer to computer as a message makes its way across the Internet, TCP operates at a higher level, concerned only with the two end systems, for example a Web browser and a Web server. In particular, TCP provides reliable, ordered delivery of a stream of bytes from a program on one computer to another program on another computer. Besides the Web, other common applications of TCP include e-mail and file transfer. Among its other management tasks, TCP controls message size, the rate at which messages are exchanged, and network traffic congestion.