LESSON 3 ENGLISH

3.1 Networking Terms

Half-duplexing - A communication method,
which can carry data in either direction but not
both directions at once.

Full-duplexing - A term used to describe
a communications channel down which data
can travel in both directions at once.

LAN - Local Area Network. A data
communications network, which is geographically,
limited (typically to a 1 mile radius) allowing easy
interconnection of terminals, microprocessors
and computers within adjacent buildings.
Ethernet, Token-ring, and FDDI are examples
of standard LANs.

WAN - Wide Area Network. Usually constructed
with serial lines, extending over distances greater
than one mile.

Server - A computer, which provides some service
for other computers, connected to it via a network.
The most commonexample is a file server, which
has a local disk andservices requests from remote
clients to read and write files on that disk.

Workstation - A general-purpose computer
designed to be used by one person at a time
and which offers higher performance than
normally found in a personal computer, especially
with respect to graphics, processing power and the
ability to carry out several tasks at the same time.
A device, which accesses available resources from
servers typically found in a distributed processing
environment .

Host - A computer connected to a network.
The term node includes devices such as routers
and printers, which would not normally be
called "hosts".

Peer-to-Peer Network - A network that does
not rely on the use of a central file server to share
files. Each workstation relies on another workstation
to have it's resources made available. They are very
difficult to maintain security, must be limited
number of peers to keep administration costs low,
slow response time, but they are inexpensive ,
no central point of failure and no special training required.

Server-based network - Requires a central file
server and a networking operating system that can
handle the job. They require a separate machine
and therefore expensive hardware, expensive NOS,
and without the proper training it is difficult to install
and maintain. On the other hand, data transfer speeds
are greater, security is more robust, LAN expansion
is simpler, and there are management tools available.

Cable - provides the pathway for network
communications. It's a component of a topology
determined by the NIC and standard being used.
The most common types of LAN cabling are coaxial,
unshielded twisted pair, shielded twist pair, and fiber optic.

NIC - An adapter circuit board installed in
a computer to provide a physical connection to a network.

Hub - A wiring concentrator for a LAN or WAN
that providesa central attachment point for network
cabling. Coaxial cable doesn't use hubs. There are
three types of hubs:
passive (absorbs some signal; no electronics to
process data signal),
active (cleans signal; electronics to amplify signal),
and intelligent (managed & switching hubs).
Switching hub - Intelligent hub, which contains
circuitry that very quickly, routes signals between
ports on the hub. A communications paradigm
in which a dedicated communication path is
established between the sender and receiver
along which all packets travel. The telephone
system is an example of a circuit switched network.
Also called connection-oriented.

MAU - Media Access Unit. In a Token Ring
network, a device to attach multiplenetwork
stations in a star topology, internally wired
to connect the stations into a logical ring.
The MAU contains relays to short out
non-operating workstations. Multiple MAUs
can be connected into a larger ring through
their Ring In/Ring Out connectors. Transceivers
( Transmitter-receiver) . The physical device, which
connects a host interface (e.g. an Ethernet controller)
to a local area network. Ethernet transceivers contain
electronics that apply signals to the cable and sense
other host's signals and collisions.

MAC address - Also known as the physical
addresses, operates on the data link layer.
Each address is a unique 12-digit hexadecimal
ID number, which is hard coded to the network
adapter by the factory , and is used by devices
to direct packets to other devices. Crossover cable
- A cable used to daisy-chain two network hubs
together. Can also be used to connect two PCs
together and eliminate the need for a hub.

Default Gateway - The exit and entry point
of a subnet. Subnetwork - A portion of a network,
which may be a physically independent network
segment, which shares a network address
with other portions of the network and is
distinguished by a subnet number.
A subnet is to a network what a network is
to an Internet.

Connectionless Protocol - The data
communication method in which communication
occurs between hosts with no previous setup.
Packets sent between two hosts may take
different routes. UDP is a connectionless
protocol. Also called packet switching. This is
on contrast to circuit switching, which is
connection-oriented. Connection
-oriented Protocol - A type of transport layer
data communication service that allows a host
to send data in a continuous stream to another host.
The transport service will guarantee that all data
will be delivered to the other end in the same order
as sent and without duplication. Communication
proceeds through three well-defined
phases: connection establishment, data transfer,
and connection release. The most common
example is Transmission
Control Protocol (TCP).

Attenuation - The degrading of a signal as it
travels farther from its origination. Crosstalk
- Signal overflow from one wire to another
adjacent wire. Jitter - Instability in a signal
wave; Caused by signal interference or an
unbalanced FDDI Ring or Token Ring.

NOW WE HAVE FINISHED
THE THIRD LESSON , THE NEXT
LESSON I WILL EXPLAIN THE
PROTOCOLS USED IN NETWORKING .

SEE YOU