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Glossary
GL-14
Cisco 10008 Router Hardware Installation Guide
OL-0659-13
U
Unchannelized DS3
See Clear channel DS3.
Unicast
A message sent to a single network destination. Compare with Broadcast and Multicast.
V
Virtual Private
Network
See VPN.
VLAN
Virtual LAN. A group of devices on one or more LANs that are configured (using management
software) so that they can communicate as if they were attached to the same wire, when in fact they are
located on a number of different LAN segments. Because VLANs are based on logical instead of
physical connections, they are extremely flexible.
VoIP
Voice over IP. Voice over IP enables a router to carry voice traffic (for example, telephone calls and
faxes) over an IP network.
VPN
Virtual private network. A secure, end-to-end private network constructed over a third-party or public
network such as the Internet.
VT-n
Virtual tributary level n. The SONET format for mapping a lower-rate signal into a SONET payload.
For example, VT-1.5 is used to transport a DS1 signal. See also DS1 and SONET.
W
WAN
Wide-area network. A data communications network that serves users across a broad geographic area
and often uses transmission devices provided by a common carrier (such as a telephone company or
service provider).
Weighted Fair
Queuing
See WFQ.
Weighted Random
Early Detection
See WRED.
WFQ
Weighted Fair Queuing. Congestion management algorithm that identifies conversations (in the form
of traffic streams), separates packets that belong to each conversation, and ensures that capacity is
shared fairly between these individual conversations. WFQ is an automatic way of stabilizing network
behavior during congestion and results in better performance and fewer retransmissions.