The directory services included with Windows Server 2003. Based on the DNS hierarchy, Active Directory provides a domain-based directory service for organizing all the objects and services in a Windows Server 2003 network.
Active Directory Users and Computers
An MMC management console provided in Windows 2000 and Windows Server 2003 Active Directory domains that can be used to administer Active Directory objects.
address pool
The available IP addresses within a scope for dynamic assignment by the DHCP server to DHCP clients.
address reservation
See reservation.
adjacency
A term in routing that refers to the record that a router keeps about the state of its connectivity with a neighbor and the attributes of the neighboring router.
administrative share
A hidden share, created by the Windows installation process. Administrative shares may not be permanently removed and are identified by a trailing $ in the name (for example, C$, D$). Any share name appended with a $ is a hidden share. Only shares created at installation are considered administrative shares.
aging
The DNS-related process of placing a timestamp on a dynamically created resource record and then tracking the age of that record.
AH (Authentication Header)
A protocol in the IPSec suite that is used to authenticate IP traffic. The AH is inserted into the original IP packet immediately after the IP header.
area
In an OSPF routing environment, a logical grouping of routers within the OSPF hierarchy.
area border router
A router with multiple interfaces that participates in multiple areas.
ARP (Address Resolution Protocol)
A protocol that is used to provide address translation from an IP address of a host to the host's physical address on the network. A host that wants to obtain a physical address broadcasts an ARP request onto the TCP/IP network. The host on the network that has the IP address in the request then replies with its physical hardware address.
ARP (Address Resolution Protocol) table
The table of IP-to-MAC address translations that is used by a router to identify the physical addresses of devices on a local subnet.
AS (autonomous system)
A collection of networks that are under common administration and share a common routing strategy. Each AS can be further divided into areas, with areas being linked by an OSPF backbone, which is also an area.
auditing
The process of logging information about network activities such as user logins, system shutdowns, and file access.
authentication
The process of verifying a user's identity on a network.
authoritative zone server
A DNS name server that supports the name database for a domain.
Automatic Updates
The client-side portion of the WSUS solution. Automatic Updates can be configured to work with the Microsoft Windows Update Web servers or with internal WSUS servers.
autostatic update
A request from a router for all known routes or services from the router on the other side of the connection. After the request is received, the router adds the requested routes to its routing table. An autostatic update is a one-time, one-way exchange of routing information.
