Glossary

P

Packet
A unit of data exchanged at the network layer. This is a much abused definition and the terms "frame" and "packet" are frequently interchanged.

Patch Cable
A twisted-pair or fiber optic jumper cable used to make a connection between a media segment and a network interface (on a station) or a network port (on a hub), or to directly connect stations and hub ports together.

PAUSE
A unique frame sent by full-duplex capable stations to indicate to the sender to slow down transmissions.

PHY
Physical Layer Device. The name used for a transceiver in Fast Ethernet and Gigabit Ethernet systems.

Physical Layer
The bottom layer in the OSI seven-layer reference model. This layer is responsible for physical signaling-including connectors, timing, voltages, and related issues. Data sent over the physical layer are termed symbols.

PoE
A solution where electrical current is run to networking hardware over the Ethernet Category 5 or higher data cabling.

Point-to-Point Technology
A network system composed of point-to-point links. Each point-to-point link connects two and only two devices-one at each end. Devices could be DTEs or DCEs, but no more than two can be connected on one link.

Port
A connection point for a cable. Repeater hubs and switching hubs typically provide multiple ports for connecting Ethernet devices.

Port Mirroring
Port Mirroring allows a switch port to monitor packets from any or all of its ports so that traffic can be analyzed.

Port Security
Prevents a switch port from learning MAC addresses. Thus, frames pass through only if their destinations are listed in the switch address look-up table. Static addresses are not affected. This feature is typically used to limit device access to a network.

Protocol
A set of agreed-upon rules and message formats for exchanging information among devices on a network.