Cisco ONS 15327 User Documentation page 534

Glossary
Optical receiver
An opto-electric circuit that detects incoming lightwave signals and converts them to the appropriate signal for processing by
the receiving device.
Orderwire
Equipment that establishes voice contact between a central office and carrier repeater locations.
Output contacts
Used to drive visual or audible devices such as bells and lights. Output contacts can control other devices such as generators,
heaters, and fans.
P
Packet
Logical grouping of information that includes a header containing control information and (usually) user data. Packets are most
often used to refer to network-layer units of data. The terms datagram, frame, message, and segment are also used to describe
logical information groupings.
Passive devices
Components that do not require external power to manipulate or react to electronic output. Passive devices include capacitors,
resisters, and coils.
Path Layer
The segment between the originating equipment and the terminating equipment. This path segment can encompass several
consecutive line segments or segments between two SONET devices.
Payload
Portion of a cell, frame, or packet that contains upper-layer information (data).
PCM
Pulse Code Modulation. Transmission of analog information in digital form through sampling and encoding with a fixed
number of bits.
Ping
Packet internet grouper. ICMP echo message and its reply. Often used in IP networks to test the connection to a network device.
PPMN
Path-protected mesh network. PPMN extends the protection scheme of a unidirectional path switched ring (UPSR) beyond the
basic ring configuration to the meshed architecture of several interconnecting rings.
Priority queuing
Routing feature that divides data packets into two queues: one low-priority and one high-priority.
Cisco ONS 15327 User Documentation, R3.3
GL-10
June 2002