LOCAL
AREA NETWORK (LAN) TECHNOLOGY
·
10/100/1000 Mbps Ethernet
·
100 Mbps FDDI
·
155/620 Mbps ATM
·
4/10/45 Mbps Wireless
What is a Protocol?
•
A protocol is a set of
rules that governs the communications between computers on a network.
•
These rules include
guidelines that regulate the following characteristics of a network:
1.
access method,
2.
allowed physical
topologies,
3.
types of cabling, and
4.
speed of data transfer.
Protocol
•
Protocol (communications
protocol)= standards that specifically address how the devices on a network
communicate, i.e
1.
How the data is packaged
for transmission
2.
How receiving devices
acknowledge signals from sending devices
3.
How errors are detected and
handled
Protocol
Logical topologies are bound to network protocols and
describe how data is moved across the network.
•
Ethernet, LocalTalk,Token
ring for wired networks
•
TCP/IP and WAP for internet
•
WiFi for wireless networks
•
Bluetooth, for short range
wireless network
Protocol : Ethernet
•
the most widely used wired
networks protocol
•
Early Ethernet network were
half duplex, uses an access method called CSMA/CD (Carrier Sense Multiple
Access/Collision Detection) a system where LAN Technology Detection), each
computer listens to the cable before sending anything through the network to
avoid collisions.
•
Since 1997 Ethernet uses
full duplex communication, that does not require listening to other messages
and no collisions occur.
•
The Ethernet protocol
allows for linear bus, star, or tree topologies. Data can be transmitted over wireless
access points, twisted pair, coaxial, or fiber optic cable.
•
Early Ethernet protocols
(10BASE-T) support 10BASE transmissions rate 10 Mbps
•
Today
1.
100BASE-T or 100BASE-TX –
1000Mbps (1Gbps
2.
10Gigagbit Ethernet –
10Gbps
Protocol : Localtalk
•
a network protocol that was
developed Macintosh computers.
•
used a method called
CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance), where a computer
signals its intent to transmit before it actually does so.
•
allows for linear bus,
star, or tree topologies using twisted pair cable.
•
disadvantage : slow speed
(only 230 Kbps).
Protocol : Token Ring
•
developed by IBM in the
mid-1980s.
•
access method involves
token-passing.
•
the computers are connected
so that the signal travels around the network from one computer to another in a
logical ring.
•
A single electronic token
moves around the ring from one computer to the next. If a computer does not
have information to transmit, it simply passes the token on to the next
workstation. If a computer wishes to transmit and receives an empty token, it
attaches data to the token. The token then proceeds around the ring until it
comes to the computer for which the data is meant- the data is captured by the
receiving computer
CABLING
•
Cable is the medium through
which information usually moves from one network device to another .
•
several types of cable are commonly
used with LANs.
•
In some cases, a network
will utilize only one type of cable, other networks will use a variety of cable
types
Types of Cables
1.
Unshielded Twisted Pair (UTP)
Cable
2.
Shielded Twisted Pair (STP)
Cable
3.
Coaxial Cable
4.
Fiber Optic Cable
1. Unshielded
Twisted Pair (UTP) Cable
The cable has four pairs of wires inside the jacket. Each
pair is twisted with a different number of twists per inch to help eliminate
interference from adjacent pairs and other electrical devices.
The standard connector for unshielded twisted pair cabling
is an RJ-45 connector
A disadvantage of UTP is that it may be susceptible to radio
and electrical frequency interference.
1.
Shielded Twisted Pair
(STP) Cable
STP is a type of cable consists of two individual
wires wrapped in a foil shielding to help provide a more reliable data
communication.
•
suitable for environments
with electrical interference;
•
however, the extra shielding
can make the cables quite bulky.
•
often used on networks
using Token Ring topology.
2.
Coaxial Cable
Coaxial cabling has a single copper conductor at its center.
A plastic layer provides insulation between the center
conductor and a braided metal shield
The metal shield helps to block any outside interference
from fluorescent lights, motors, and other computers.
Coaxial Cable Connectors
• The most common type of connector used with coaxial cables
is the BayonetllCl ( C) Neill-Concelman BNC) connector
• Different types of adapters are available for BNC
connectors, including a Tconnector, barrel connector, and terminator.
4. Fiber
Optic Cable
• consists of a center glass core surrounded by several
layers of protective materials
• It transmits light rather than electronic signals
eliminating the problem of electrical interference.
• ideal for certain environments that contain a large amount
of electrical interference..
• able to transmit signals over much longer distances than
coaxial and twisted pair.
NETWORK OPERATING SYSTEM (NOS)
•
Software that controls a
network and its message (e.g. packet) traffic and queues, controls access by
multiple users to network resources such as files, and provides for certain
administrative functions, including security. coordinate the activities of
multiple computers
•
across a network.
•
acts as a director to keep
the network running smoothly.
•
A NOS is not the same as
the networking tools provided by some existing OSs, Windows XP for instance.
•
An NOS is an OS that has
been specifically written to keep networks running at optimal performance.
•
Some popular NOSs include:
•
Windows NT , IBM AIX, Sun
Solaris, Windows 2000 Server, Windows Server 2003,Inferno Novell NetWare, Red
Hat Linux, BSD
•
The two major types of
network operating systems are: :
1.
Peer to Peer
2.
Peer-to-– Client/Server
1. Peer
to Peer
·
In a peer-to-peer network,
all computers are considered equal; they all have the same abilities to use the
resources available on the network
•
allow users to share
resources and files located on their computers and to access shared resources
found on other computers.
•
do not have a file server
or a centralized management source
•
designed primarily for
small to medium local area networks.
•
AppleShare and Windows for
Workgroups are examples of programs that can function as peerto- peer network
operating systems.
Advantages
•
Less initial expense - No
need for a dedicated server.
•
Setup - An operating system
such asWindows XP/…) already in place may onlyneed to be reconfigured for
peer-to-peer operations.
Disadvantages
•
Decentralized - No central
repository for files and applications.
•
Security - Does not provide
the security available on a client/server network.
2. Peer-to-–
Client/Server
allow the network to centralize functions and applications
in one or more dedicated file servers
•
the file servers become the
heart of the system, providing access to resources and providing security.
•
individual workstations
(clients) have access to the resources available on the file servers.
•
Novell Netware and Windows
2000 Server are examples of client/server network operating systems.
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