Glossary
Bandwidth
The width of a communication channel, measured
as frequency (hertz) or bits per second (bps).
Baudrate
The speed of information being transmitted across a
serial interface, expressed in units of bits per second
(bps). For example, a baud rate of 9600 refers to bits
being transmitted (or received) from one piece of
equipment to another at a rate of 9600 bps. Thus,
a seven bit ASCII character plus parity bit plus one
stop bit (total nine bits) would be transmitted in
9/9600 sec. = 0.94 ms or about 1000 characters/sec.
When communicating via a serial interface, the baud
rate settings for two pieces of equipment must match.
Bit
A binary digit - either 0 or 1. Abbreviated b for bit
or bits.
Bit Rate (BR)
The rate of data throughput on a medium
(measured in bps or Hz, whichever is more
appropriate to the context).
CBR (Constant Bit Rate)
A term that describes how video or audio is encoded.
Constant bit rate means that the bit rate doesn’t
vary during the video or audio at all, but is same
through the clip.
CIF - Common Intermediate Format
A commonly used television standard for measuring
resolution. QCIF equals 176 x 120 pixels for NTSC
and 176 x 144 pixels for PAL. CIF equals 352 x 240
pixels for NTSC and 352 x 288 pixels for PAL.
2CIF equals 704 x 240 pixels for NTSC and 704 x 288
pixels for PAL. 4CIF equals 704 x 480 pixels for NTSC
and 704 x 576 pixels for PAL.
Client/Server
A model of computing in which a desktop client
application has the necessary intelligence to access
servers or hosts on the network to request informa-
tion or perform queries about available resources.
Command Line Interface (CLI)
A text-based user interface. Allows the user to
interact with the operating system by entering
commands and optional arguments.
DHCP (Dynamic Host Confi guration Protocol)
Internet standard (RFC 1541) protocol for distributing
confi guration information to network and allows a
computer to obtain its own IP address automatically
rather than having it entered manually.
Ethernet
Specifi ed in a standard, IEEE 802.3. 10BASE-T
Ethernet systems provide transmission speeds up to
10 Mbps. Fast Ethernet or 100BASE-T provides
transmission speeds up to 100 megabits per second
and is typically used for LAN backbone systems,
supporting workstations with 10BASE-T cards.
Gigabit Ethernet provides an even higher level of
backbone support at 1000 megabits per second
(1 gigabit or 1 billion bits per second).
Fast Ethernet
Also referred to as 100Base-Tand 100Base-X.
Uses CSMA/CD access method at 100 Mbps;
IEEE 802.3u; MII replaces AUI. Can use full duplex
(200 Mbps). 100m limit for UTP implementation.
Numerous wiring options: 100Base-TX, 100Base-T4,
100Base-FX; 4b5b/MLT-3 encoding.
A fi rewall exhibits the following properties: all traffi c
between networks must fl ow through it, only autho-
rized traffi c is allowed to pass, and the fi rewall
should be immune to compromise.
Frame Rate
An attribute (relevant just for video mostly) which
determines the video fl uency. The TV transmission in
Europe (PAL standard) has a frame rate of of 25 fps
(or more exactly 50 fi elds per second). The frame rate
in US (NTSC standard) is 30 fps.
Full Duplex
The ability to transmit and receive signals
simultaneously.
Gateway
Gateways are points of entrance to and exit from a
communications network. Viewed as a physical
entity, a gateway is that node that translates
between two otherwise incompatible networks or
network segments.
Gigabit Ethernet
Informal name for emerging standard (IEEE 802.3z)
CSMA/CD technology designed to provide 1Gbps
network connectivity. Based on existing and evolving
802.3 standards, Gigabit Ethernet is expected to
incorporate both half and full-duplex operation, link-
level fl ow control, VLAN support, and systems
management. Support for one repeater per collision
domain, backward compatibility with 10Base-T and
100Base-TX. New technologies introduced include
packet bursting and carrier extension.
For half-duplex devices carrier time and slot time are
extended to 4096 bit times. Minimum packet length
is same as existing Ethernet (64 B).
Glossary
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