Glossary
GL-5
Cisco Unified Communications Manager Configuration Guide for the Cisco TelePresence System
OL-21851-01
I
IDR
An IDR frame is a special kind of I frame used in MPEG-4 AVC encoding. IDR frames can be used to
create Advanced Video Coding (AVC) streams, which can be easily edited.
incandescent lamp
A lamp that allows an electric current to pass through a thin filament, heating it and causing it to emit
light.
Internet model (free
path)
The Internet model is an unsecured “free path” model of packet delivery: Packets are delivered in any
way possible and each uncontrolled router on the way to the destination handles how to deliver the
packet to the next stop. See
VPN model (fixed path)
.
IP address
A device identifier on a TCP/IP network.
J
jitter
jitter call
jitter period
Variation in packet transit delay caused by queuing, contention, and serialization effects on the path
through the network. In general, higher levels of jitter are more likely to occur on either slow or heavily
congested links.
Jitter call is the average jitter measurement per call. Shown in the Jitter/Call output field as part of Per
Call Jitter and Packet Loss Reporting.
Jitter period is the interval between two times of maximum effect (or minimum effect) of a signal
characteristic that varies regularly with time. Jitter frequency, the more commonly quoted figure, is its
inverse.
The CTS measures jitter every 10 seconds. The Jitter/Period field reports the jitter measurement for the
last 10-second period.
The CTS calculates jitter as the sum of the maximum deviation (both late and early) from the expected
arrival time as given by the frame period. CMA computes frame jitter based on the arrival time of the
last packet of a frame.
L
LCD
Liquid crystal display. A projector for displaying video, images or computer data on a screen or other
flat surface.
LED
Light-emitting diode. Indicators on the CTS that determine whether the user is sitting within camera
range.
light temperature
A theoretical means of describing visible light that is determined by comparing its hue with a heated
black-body radiator. The lamp’s color temperature is the temperature in kelvins at which the heated
black-body radiator matches the hue of the lamp.
