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Appendix B: Glossary
very-small-apertureterminal (VSAT)
: A small satellite dish, ranging from 2 ft. to 15 ft. (0.6 m to 4.6 m) in diameter. The size of
the VSAT depends on the site and uses.
The principal advantage in using VSATs is that a network can be developed without reliance on landlines, permitting a branch site
to be placed where it is needed, no matter how remote.
Virtual LAN : See virtual local area network.
virtual local area network (VLAN) : A group of devices within a LAN (or a group of devices located in two or more LANs)
selected to receive broadcasts intended only for that group.
Use of VLANs reduces the amount of traffic broadcast to the entire LAN.
NOTE: VLANs are described in IEEE standards 802.1q and 802.1p.
Also see VLAN broadcast.
virtual private network (VPN) : Use of encryption, authentication, and tunneling across a public network to ensure secure com-
munication between private endpoints. A VPN can implement one or more technologies to accomplish secure private
communication—for example, IPsec.
NOTE: There are several IETF RFCs that address VPNs. For a list of RFCs applicable to VPNs, see the VPN Consortium’s website:
www.vpnc.org/vpn-standards.html
Also see VPN tunneling.
Virtual Private Network Consortium (VPN Consortium, VPNC):
A trade association for manufacturers and vendors of VPN
products. The VPN Consortium tests products for VPN compliance and interoperability. The VPNC supports development of
standards for VPNs, but the VPNC itself does not develop standards.
For a list of RFCs applicable to VPNs, see the VPN Consortium’s website:
www.vpnc.org/vpn-standards.html
Virtual Router Redundancy Protocol (VRRP) : A protocol for providing continuous router support to a network.
NOTE: VRRP and VBRS™ are sometimes confounded but are unrelated. Both processes provide redundancy, but in different ways.
VLAN : See virtual local area network.
VLAN broadcast : A broadcast directed to a specified VLAN.
NOTE: VLAN broadcasts reduce the amount of traffic sent to the entire LAN.
VPN
: See virtual private network.
VPN Consortium : See Virtual Private Network Consortium.
VPN tunneling : The use of tunneling on a VPN.
NOTE: VPN tunneling includes the ability, if desired, to encrypt the source address, destination address, and data in order to
provide protection for encapsulated packets. Also see tunnel mode, IP Security Protocol.
VRRP
: See Virtual Router Redundancy Protocol.
VSAT : See very-small-aperture terminal.
wavelengthdivision multiple access, wavelengthdivision multiplexing (WDMA, WDM) : A technology sometimes used in
fiber optic networks. WDM sends several wavelengths across one optical fiber, increasing the fiber’s carrying capacity. WDM also
allows bidirectional transmission over an optical fiber. Compare code-division multiplexing, time-division multiplexing.
WDM : See wavelength-division multiplexing.
WDMA : See wavelength-division multiple access.