INTRODUCTION:
LOCAL AREA NETWORK (LAN)
LOGICAL & PHYSICAL TOPOLOGY
TOPOLOGY IN LAN:
BUS, RING, STAR,HYBRID & MESH
TRANSMISSION TECHNIQUES BASEBAND & BROADBAND
- EP601 - LOCAL AREA NETWORK
(LAN)
DEFINITION OF LAN
1) A group of computers that shared hardware, software or data. Widely used to link a personal computer (PC) or workstation at homes, offices or plants to share sources and exchange information. 2) Covers a small area for example, a computer laboratory, school or a building. Communication system which allows variety of devices to communicate between each other in a limited geographic area (in building or a nearby buildings). 3) Usually owned, used and organized by a private organization.
DEFINITION OF LAN
The following are configuration of Local Area Network (LAN):
Server computer
NETWORK
A system that allows a group of users to communicate with each other. The users can be referred to a computer or node that is passing or using data.
Used for variety of applications; such as linking various PCs to each other and to larger computer in office or building, industrial plants, factories and scientific laboratories.
Each network application has different requirements in term of message, speed, acceptable, cost and ability to add new users.
NETWORK
The following is computer network:
NETWORK
Set of devices (node) which relates by a media link to establish a data path where information can be shares.
Terms use in computer network:
Network
Server
Source sharing to other network users or computer that runs network operational system to handle network or give service to other workstation users.
NETWORK
Node
Computer, printer or device that can send or receive data produce by other node.
Link
Communication channel.
Path
Channel where data moves.
Medium
Method or way how the computers are connected (refers to interface card).
NETWORK
Protocol
Set of rules uses to manage and handle network.
Terminal Server computer that can links to other terminal.
Client
Workstation or computer that can reach source sharing provides by server.
NETWORK
The following are terminology of computer network:
NETWORK TASK
Network
Task
Electronic communication
facilities - electronic mail,
teleconference, video, etc.
Internet facilities - email, chat,
downloading file, bulletin
board, online business
Shopping -
delivery
from
television or
radio and e-
commerce
ATM card
usage -
draw cash,
fund
transfer
TOPOLOGY 1) Topology can state how computers communicate in network. Most networks use cable as connection medium. We have to consider combinational of cables with Network Interface Card used, network operation system and other component. 2) The importance of topology is that it states how computer communicate in network. Different topology communicate in different ways. 3) Topology is an arrangement or physical layout of computer, cable and other network components. Network topology refers to basic design of network or geometry representation of relations for all lines and devices between one another. 4) Selection of a right topology must be done because it will affect the entire network.
LOGICAL AND PHYSICAL TOPOLOGY
Generally, there are two types of topology:-
1) Logical: refers to how it operates (transmit data); or how the media is accessed by the hosts.
2) Physical: real display of devices that connects in network, including location and cable installation; or how
the nodes of the network are physically connected.
TOPOLOGY in LAN
BUS Topology
STAR Topology
RING Topology
HYBRID Topology
MESH Topology
BUS TOPOLOGY
use single cable known
as segment or backbone
BUS TOPOLOGY
known as linear bus
and simplest topology
computers communicate base on data addressing to
particular computer
all stations effectively share a common bus cable
or the backbone
communication is bidirectional
to allow any one station to talk to another
station
communication is faster than other topologies (sending
station effectively broadcasts its message so all stations can
receive)
The following is configuration of bus topology:
BUS TOPOLOGY
BUS TOPOLOGY
Cheapest topology
Advantages
Any problem at nodes will interrupt the network
Disadvantages
Easy to add station
Less cable usage
Well functioning for small network
Hard to handle problem
A beginner and closure is required for backbone
Response rate is low
TRANSMISSION SIGNAL
Only one computer can send signal or data in a period of time. This condition will affect network performance when total of connected computers is increasing.
The more computers connected to network, the longer time for every computer has to wait turn to send data (network is slower).
BUS TOPOLOGY
Data in network is in a form of electronic signal. The information will be received only by computer that has address matched with address coded by the original signal.
Computer in bus topology only hear the network line to ensure whether there is data to send. These computers do not response to its next computer. If any of the computers failed, it does not affect the whole network.
BOUNCE SIGNAL
To stop signal from bouncing, terminator is required at each end of cable. Terminator will functioned to absorb signal sent so that it will not bounce and disturb another computer who waits for its turn to send data.
BUS TOPOLOGY
Data in network will moves from starting to the end of network cable. If the signal is not stopped, it will bounce in front or to the back of network line, and causing another computer to be block from sending signal or data. Thus the signal has to be stopped.
TERMINATOR
STAR TOPOLOGY
STAR
TOPOLOGY?
star network is used mostly in Ethernet and
LAN
star topology reduces
chance of network failure by
connecting all of the systems
to a central node
computers and devices in the network are connected
to a central master computer known as hub
communication must take place through the hub that allows any
user to be linked up with any other user
central hub rebroadcasts all transmissions received from
any peripheral node to all peripheral nodes on network,
sometimes including the originating node
The following are configuration of star topology:
STAR TOPOLOGY
Server
Computer
Printer
iBook Tower PC
HUB
STAR TOPOLOGY
Connection process is easy
Advantages
Requires longer cable than bus topology
Disadvantages
Installation and elimination process will not interrupt
network system
Any damages to network system can be detected
Cost is higher compares to bus topology
If hub break downs, all nodes cannot functioned
in the network
RING TOPOLOGY
if only one unit of MSAU is used, then
physically it is same as
connection of star topology
RING TOPOLOGY
known as token ring (connects all nodes into a circle
of chain /ring)
addition device is required in ring
topology, known as Multi Station
Access Unit (MSAU)
message or data will be transferred
by sequence through a same route and ring
every data that pass through the
node will have to check its
delivery location
if the node does not match, then it has to be passed to the next node
until it finds the matching node
(destination address)
The following is configuration of ring topology:
RING TOPOLOGY
Ring Topology
RING TOPOLOGY
No collision
Advantages
Only one device can transmit data on the
network at a time
Disadvantages
Data transferring using high speed
Seldom used
Any damages on connection will interrupts the whole
system Easy to detect problem
Required many cables
HYBRID TOPOLOGY
HYBRID TOPOLOGY
combination of any two or more topologies, resulting network does
not exhibit one of the standard topology
passive hub will only acts as source of connection
that does not strengthen or
regenerate any signal
two common examples for
hybrid network are: star-ring network and
star bus network.
active hub will regenerate
electrical signal received before it send the signal to
all computers connected in
topology
star-ring network consists of two or more star topologies is connected using a MSAU
as a centralized hub while a star-bus network consists of two or more star
topologies connected using a bus trunk (the bus trunk serves as the network's
backbone).
The following is configuration of hybrid topology:
HYBRID TOPOLOGY
HYBRID TOPOLOGY
Reliable and scalable
Advantages
Complexity of design
Disadvantages
Flexible (design for different network
environment)
Effective in combination and the speed is consistent
Installation and configuration is difficult
Highly cost of hub and infrastructure
MESH TOPOLOGY
router is used to search
multiple paths and determine the best path
for data
MESH TOPOLOGY
refers to a Wide Area Network
(WAN)
connecting multiple sites; and reliability is important as number of sites being
connected together.
a mesh is best suited for
situations where it will not need to
be moved or expanded beyond
five sites or nodes
three or four sites mesh network is relatively
easy to create, whereas it is impractical to set up a mesh network of
100 sites or nodes
The following is configuration of mesh topology:
MESH TOPOLOGY
FULL MESH
MESH TOPOLOGY
Occurs when every node has a circuit connecting it to every other nodes in network.
Very expensive to implement and yields the great amount of redundancy (if one node fails, network traffic can be directed to other nodes).
Usually reserved for backbone networks.
PARTIAL MESH
MESH TOPOLOGY
Some nodes are organized in a full mesh scheme, but others only connected to one or two in network.
Less expensive to implement and yields less redundancy compares to full mesh topology.
Commonly found in peripheral networks connected to a full meshed backbone.
MESH TOPOLOGY
Data can be transmitted from different devices
simultaneously
Advantages
High chances of redundancy in many network connections
Disadvantages
If one components fails there is always alternative
Expansion and modification in topology can be done
easily
Setup and maintenance of network is difficult
Overall cost of this network is way too high
TRANSMISSION TECHNIQUES
BASEBAND
BROADBAND
BASEBAND
BASEBAND
Digital data is
applied directly
to medium and
the entire
bandwidth of
medium is
used by signal.
Means no carrier is modulated,
which refers to data or
information signal whether it is
binary, analog voice or video.
Cable attenuation and distortion greatly limit
the transmission distance, up to 1 mile with
twisted pair and 5 mile with coaxial cable.
Such systems are
simple,
inexpensive and
easy to work with,
but only one
signal can be
carried on the
medium at a time.
BASEBAND CHARACTERISTICS
BASEBAND
Baseband provides single channel for the whole bandwidth where it is not divided into channels. It carries different kind of information using Time Division
Multiplexing (TDM) where the time slot is use by turns. Baseband also use digital transmission which does not required
modem, however for voice, modem is required. Bandwidth is not necessarily huge if using baseband cable
between PC. Maximum baseband transmission is 10Mbps or high.
BASEBAND ADVANTAGES Baseband technique is less expensive and easier to install.
The following are configuration of baseband:
BASEBAND
Coaxial cable signal
Point to point
Multidrop
BROADBAND
BROADBAND
Data signals
can be
translated up
in frequency
to specific
channels.
Broadband
has
bandwidth of
up to 300 to
450 MHz.
Means data signals
modulate a higher-frequency
carrier (analog methods are
used to transmit digital data).
This system is more complex
and expensive because
modems are required at each
node.
An enormous
number of high
speed channels
can be created.
In addition,
transmission
over longer
distances (up to
10 mile) on
coaxial cable
can be
achieved.
BROADBAND CHARACTERISTICS
BROADBAND
Broadband bandwidth is divided into channels to provide sub channels for communication and enables information transferring in parallel. It use Frequency Division Multiplexing (FDM) because each channel carries different frequency. FDM devices usually called as modem RF. FDM also allows several conversations to coexist on the LAN simultaneously. Broadband techniques involved modulation and demodulation process, and frequency filtering.
BROADBAND ADVANTAGES
Broadband technique can accommodate many channels, for example 20 to 30 channels per cable.
The following are configuration of broadband:
BROADBAND
Schematic cable
Bandwidth
Schematic RF
Baseband vs. Broadband
Baseband communication is bi-directional, which same channel can be used to send and receive signals. However, the sending and receiving cannot occur on the same wire at the same time.
Broadband communication is unidirectional, so in order to send and receive, two pathways are needed.
Using Baseband transmissions, it is possible to transmit multiple signals on a single cable by using a process known as multiplexing. Baseband uses Time-Division Multiplexing (TDM), which divides a single channel into time slots.
Multiple channels are created in a broadband system by using a multiplexing technique known as Frequency-Division Multiplexing (FDM). FDM allows broadband media to accommodate traffic going in different directions on a single media at the same time.
Baseband vs. Broadband
Data signals can be sent over a network cable in one of two ways: broadband or baseband.
Baseband, data is sent as digital signals through the media as a single channel that uses the entire bandwidth of the themselves take the form of either electrical pulses or light.
Broadband uses analog signals in the form of optical or electromagnetic waves over multiple transmission frequencies. Each transmission is assigned to a portion of the bandwidth, hence multiple transmissions are possible at the same time.
COMPARISON OF BASEBAND AND BROADBAND
BASEBAND AND BROADBAND
No Characteristics Baseband Broadband
1 Main channel division
single channel systems that use the entire bandwidth divided into several subchannels
2 Bandwidth length
not necessarily wide
greater bandwidth to accommodate many subchannels, up to 20-30 subchannels
3 Multiplexing technique
use time-division multiplexing (TDM) which divides a single channel into time slots to allow multiple channels over a single baseband transmission line, thus serial transmission
use frequency division multiplexing (FDM) to create multiple broadband channels, thus parallel transmission (multiple transmissions are possible at the same time)
COMPARISON OF BASEBAND AND BROADBAND
BASEBAND AND BROADBAND
No Characteristics Baseband Broadband
4 Signal type digital (unmodulated) , no need of modems
analog or digital signal onto RF carrier (Analog), use modem
5 Speed up to 10 Mbps up to 180 Mbps
6 Distance short distances up to a few kilometres
long distances up to tens of kilometres
7 Direction
bidirectional so that a baseband system can both transmit and receive signals simultaneously
unidirectionaltraveling in only one direction at a timeso a broadband system can generally either transmit or receive but cannot do both simultaneously