Specifications

Glossary
GL-13
Cisco ONS 15454 Troubleshooting and Maintenance Guide
November 2001
VLAN
Virtual LAN. Group of devices located on a number of different LAN segments that are configured (using management
software) to communicate as if they were attached to the same wire. Because VLANs are based on logical instead of physical
connections, they are extremely flexible.
VPN
Virtual Private Network. Enables IP traffic to travel securely over a public TCP/IP network by encrypting all traffic from one
network to another. A VPN uses “tunneling” to encrypt all information at the IP level. (See also Tunneling.)
VT
Virtual Tributary. A structure designed for the transport and switching of sub-DS3 payloads.
VT layer
The VT layer or electrical layer occurs when the SONET signal is broken down into an electrical signal.