Created and used in cases where an OSPF area cannot have direct physical access to the backbone. In this instance, it is necessary to configure a connection from the new area to the backbone through a connection called a virtual link. The virtual link gives the disconnected area a logical path to the backbone. The virtual link has to be established between two area border routers that have a common area, with one area border router connected to the backbone.
VLSM (variable-length subnet mask)
A subnet mask that is used either to split a large network into smaller pieces (subnetting) or combine smaller networks into a larger one (supernetting).
VPN (virtual private network)
A mechanism for providing secure, private communications, utilizing a public network (such as the Internet) as the transport method. VPNs use a combination of encryption and authentication technologies to ensure data integrity and security.
Windows Internet Naming Service (WINS)
A service that runs on a Windows Server 2003 server to provide NetBIOS name resolution. When you use WINS, name resolution is performed using directed transmissions, resulting in a reduction in broadcast traffic and the capability to find systems on different subnets. WINS replaces the LMHOSTS file in a fashion similar to the way DNS replaced the HOSTS file.
WSUS (Windows Server Update Services)
An add-on service for Windows 2000 and Windows Server 2003 networks that provides the functionality of a Windows Update Web server on the internal network. WSUS allows you to select which available updates are authorized for distribution to network clients, thus ensuring that only the updates you have tested and approved are installed.
