Installation manual

Glossary-5
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Network Time Protocol (NTP)
NTP provides the mechanisms to synchronize time across the network. The time servers
operate in a hierarchical-master-slave configuration in order to synchronize local clocks
within the subnet and to national time standards via wire or radio.
Out-of-Band Management
Management of the network from a station not attached to the network.
Port Authentication
See IEEE 802.1X.
Port Mirroring
A method whereby data on a target port is mirrored to a monitor port for troubleshooting
with a logic analyzer or RMON probe. This allows data on the target port to be studied
unobstructively.
Port Trunk
Defines a network link aggregation and trunking method which specifies how to create a
single high-speed logical link that combines several lower-speed physical links.
Power over Ethernet
The IEEE 802.3af standard for providing Power over Ethernet (PoE) capabilities. When
Ethernet is passed over copper cable, two twisted pairs are used for data transfer, and
two twisted pairs are unused. With PoE, power can either be passed over the two data
pairs or over the two spare pairs.
Private VLANs
Private VLANs provide port-based security and isolation between ports within the
assigned VLAN. Data traffic on downlink ports can only be forwarded to, and from, uplink
ports.
QinQ Tunneling
QinQ is designed for service providers carrying traffic for multiple customers across their
networks. It is used to maintain customer-specific VLAN and Layer 2 protocol
configurations even when different customers use the same internal VLAN IDs.
Quality of Service (QoS)
QoS refers to the capability of a network to provide better service to selected traffic flows
using features such as data prioritization, queuing, congestion avoidance and traffic
shaping. These features effectively provide preferential treatment to specific flows either
by raising the priority of one flow or limiting the priority of another flow.