2020 network topologies and access methods

Network topologies and
access methods - Agenda
 5 min Warm up Essential Question brain storm
 15 min Introduction teacher demonstrate
 10 min Act1 – ppt teacher demonstrate
 5 min Act2 - listen to Lan video then asking questions
 10 min Students are connecting LAN between 2 laptops
 10 min Act3 - teacher demonstrate “Network Operating Software”
 10 min Act4 – network access methods
 2 +3 min Act5 - listen to access methods video then
asking questions
 10 min Reflection
 Home work Eng.Osama Ghandour
Programming and electronics
Teacher
Assiut STEM School1

Essential Questions:
you were asked to create
network between your
school labs ,identify how
will you plan to do this
task?
Eng.Osama Ghandour Programming and electronics Teacher
Assiut STEM School2

How could to know about network
topologies and access methods?
 Example Movie
makerAsk or call a
college
Ask a
teacher
Ask or call an
expert or an
engineer
Search through search
engine such as google
or Bing for ppt or pdf
files using your laptop
or smart phone through
internet connection
Use the help / F1
Search through
YouTube
Search through wiki
Beddia
Activity 2
Eng.Osama Ghandour
Teacher
Assiut STEM School3

CS.2.07 Brain storm 5 min
Essential Questions:
What are the kinds
of networks ?
15-4
Eng.Osama Ghandour
Teacher
Assiut STEM School

5
biomimicry
computer
network
Eng.Osama Ghandour
Teacher
Assiut STEM School

Geographically
LAN
WAN
MAN
Eng.Osama Ghandour
Teacher
Assiut STEM School6

Introduction teacher demonstrate
Topology 15 min
 The physical topology of a network refers to the
configuration of cables, computers and other
peripherals.
 The main types of network topologies are:
– Linear Bus
– Star
– Ring
– Tree or Hybrid
Eng.Osama Ghandour
Teacher
Assiut STEM School7

Linear Bus topology
 A linear bus topology consists of a main run of cable with a
terminator at each end. All servers workstations and
peripherals are connected to the linear cable , a bus
technology called Ethernet has become the
industry standard for local-area networks.
Eng.Osama Ghandour
Teacher
Assiut STEM School8

Eng.Osama Ghandour
Teacher
Assiut STEM School9

Advantages & Disadvantages of Bus Topology
Advantages
 Works well for small networks
 Relatively inexpensive to implement
 Easy to add to it
Disadvantages
 Management costs can be high
 Potential for congestion with network trafficEng.Osama Ghandour
Teacher
Assiut STEM School10

Star topology
 A star network is
designed with each
node (file server,
workstation,
peripheral) connected
directly to a central
network hub or server
Eng.Osama Ghandour
Teacher

Eng.Osama Ghandour
Teacher

Advantages & Disadvantages of Star Topology
Advantages
 Good option for modern networks
 Low startup costs
 Easy to manage
 Offers opportunities for expansion
 Most popular topology in use; wide variety of
equipment available
Disadvantages
 Hub is a single point of failure
 Requires more cable than the bus
Eng.Osama Ghandour
Teacher

Ring topology
 A ring network is one
where all workstations
and other devices are
connected in a
continuous loop. There
is no central server
Eng.Osama Ghandour
Teacher

Eng.Osama Ghandour
Teacher

Advantages of Ring Topology
 Easier to manage; easier to locate a
defective node or cable problem
 Well-suited for transmitting signals over
long distances on a LAN
 Handles high-volume network traffic
 Enables reliable communication
Eng.Osama Ghandour
Teacher

Disadvantages of
Ring Topology
 Expensive
 Requires more cable and network
equipment at the start
 Not used as widely as bus topology
– Fewer equipment options
– Fewer options for expansion to high-
speed communication
Eng.Osama Ghandour
Teacher

Eng.Osama Ghandour
Teacher

Tree or hybrid topology
 A tree or hybrid
topology combines
characteristics of linear
bus and star and/or
ring topologies.
 It consists of groups of
star-configured
workstations connected
to a linear bus
backbone cable
Eng.Osama Ghandour
Teacher

Star-Wired Bus
Eng.Osama Ghandour
Teacher

Star-bus-Topology - Star-
ring Topology
Eng.Osama Ghandour
Teacher
(CSMA/CD)

 Explain the principles of
networking, describe types of
networks, explain basic
networking concepts and
technologies, describe the
physical components of a network.
 describe network topologies,
Identify Ethernet standards
Eng.Osama Ghandour
Teacher

15 min Act1 – TPS
-Searching about Network
topologies
-Students print A3 and A4
papers about Network
topologies then stick it at the
class room walls Eng.Osama Ghandour
Teacher

Daisy chain: linked series of devices
– Hubs and switches often connected in daisy
chain to extend a network
Hubs, gateways, routers, switches, and
bridges can form part of backbone
Extent to which hubs can be connected is
limited
Backbone Networks: Serial
Backbone
Eng.Osama Ghandour
Teacher

10 min Act3 - teacher demonstrate
“Network Operating Software”
 Network operating systems co-
ordinate the activities of
multiple computers across a
network
 The two major types of
network OS are:
– Peer-to-peer
– Client/server
Eng.Osama Ghandour
Teacher

Peer to peer network OS
– In peer to peer network OS, there is no
file server or central management source;
all computers are considered equal
– Peer to peer networks are design
primarily for small to medium LANS
– AppleShare and Windows
for Workgroups are examples of
programs that can function as peer to
peer
Eng.Osama Ghandour
Teacher

Client/Server network OS
– Client/server network OS centralise
functions and applications in one or
more dedicated file servers.
– The file server provides access to
resources and provides security
– Novel Netware and
Windows NT Server
are examples of
client/server network
operating systems
Eng.Osama Ghandour
Teacher

Eng.Osama Ghandour
Teacher
Now students
Concentrate to PPT
demonstration about
network models stopping
it then asking questions
10 m press here

Eng.Osama Ghandour
Teacher
Activity using laptops
Concentrate to PPT about
LAN between 2 laptops using
UTP
cable then asking questions
10 m press here

Network Flow of data / Computer
network access methods
 The Function of Access Methods
The set of rules that defines how a
computer puts data onto the network
cable and takes data from the cable is
called an access method. Once data is
moving on the network, access
methods help to regulate the flow of
10 min Act4 – network access methods
Eng.Osama Ghandour
Teacher

 Traffic Control on the Cable
A network is in some ways like a
railroad track, along which several trains
run. The track is interspersed with
occasional railway stations. When a
train is on the track, all other trains must
abide by a procedure that governs how
and when they enter the flow of traffic.
Without such a procedure, entering
trains would collide with the one already
on the track. Train pictures
Eng.Osama Ghandour
Teacher

What are important
differences between
a railroad system
and a computer
network?. Train pictures
Eng.Osama Ghandour
Teacher

Network Flow of data / computer
network access methods
– Carrier-sense multiple-access
with collision detection
(CSMA/CD)
– Carrier-sense multiple-access with
collision avoidance (CSMA/CA)
– Token passing Eng.Osama Ghandour
Teacher

2 min Act5 - listen
to access methods
video then asking
questions press here
Eng.Osama Ghandour
Teacher

 Carrier-sense multiple-access with
collision detection (CSMA/CD)
Collision occurs if two computers put
data on the cable at the same time35
Eng.Osama Ghandour
Teacher
Assiut STEM School

 Access methods
prevent computers from
gaining simultaneous
access to the cable. By
making sure that only
one computer at a time
can put data on the
network cable, access
methods ensure that
the sending and
receiving of network
data is an orderly
process.
Computers can
transmit data only if
the cable is freeEng.Osama Ghandour
Teacher

‫لى‬ ‫انت‬ ‫دا‬ ‫بى‬ ‫حس‬
‫حاجة‬ ‫كل‬
Eng.Osama Ghandour
Teacher

Eng.Osama Ghandour
Teacher

With these points in mind, the name of
the access method—carrier-sense
multiple access with collision detection
(CSMA/CD)—makes sense. Computers
listen to or "sense" the cable (carrier-
sense). Commonly, many computers on
the network attempt to transmit data
(multiple access); each one first listens to
detect any possible collisions. If a
computer detects a possible collision, it
waits for a random period of time before
retransmitting (collision detection).39

CSMA/CD is known as a contention method because
computers on the network contend, or compete, for an
opportunity to send data
 CSMA/CD Considerations
 The more computers there are on the network, the
more network traffic there will be. With more traffic,
collision avoidance and collisions tend to increase,
which slows the network down, so CSMA/CD can be a
slow-access method. Ex. journal exams
Eng.Osama Ghandour
Teacher

Eng.Osama Ghandour
Teacher

 After each collision, both computers will have to try to
retransmit their data. If the network is very busy, there
is a chance that the attempts by both computers will
result in collisions with packets from other computers
on the network. If this happens, four computers (the two
original computers and the two computers whose
transmitted packets collided with the original
computer's retransmitted packets) will have to attempt
to retransmit. These proliferating retransmissions can
slow the network to a near standstill.
 The occurrence of this problem depends on the number
of users attempting to use the network and which
applications they are using. Database applications tend
to put more traffic on the network than word-processing
applications do. Ex journal exams42

 Depending on the hardware components, the cabling,
and the networking software, using a CSMA/CD
network with many users running several database
applications can be very frustrating because of heavy
network traffic. Ex journal exams
Eng.Osama Ghandour
Teacher

Eng.Osama Ghandour
Teacher

2 min Act5 - listen
to Token ring
access method
video then asking
questions press hereEng.Osama Ghandour
Teacher

Token-Passing Access Method
 In the access method known as token passing, a
special type of packet, called a token, circulates around
a cable ring from computer to computer. When any
computer on the ring needs to send data across the
network, it must wait for a free token. When a free
token is detected, the computer will take control of it if
the computer has data to send.
The computer can now transmit data. Data is transmitted
in frames, and additional information, such as addressing,
is attached to the frame in the form of headers and
trailers
Eng.Osama Ghandour
Teacher

 While the token is in use by one computer, other
computers cannot transmit data. Because only one
computer at a time can use the token, no contention
and no collision take place, and no time is spent waiting
for computers to resend tokens due to network traffic
on the cable.
Eng.Osama Ghandour
Teacher

 Demand Priority Access Method
 Demand priority is a relatively new access method
designed for the 100-Mbps Ethernet standard known as
100VG-AnyLAN. It has been sanctioned and
standardized by the Institute of Electrical and Electronic
Engineers (IEEE) in its 802.12 specification, which is
discussed later in this chapter.
 This access method is based on the fact that repeaters and end
nodes are the two components that make up all 100VG-AnyLAN
networks. Figure 3.4 shows a demand-priority network. The
repeaters manage network access by doing round-robin
searches for requests to send from all nodes on the network. The
repeater, or hub, is responsible for noting all addresses, links,
and end nodes and verifying that they are all functioning.
According to the 100VG-AnyLAN definition, an end node can be
a computer, bridge, router, or switch.49

Eng.Osama Ghandour
Teacher

 Demand-Priority Contention
 As in CSMA/CD, two computers using the demand-
priority access method can cause contention by
transmitting at exactly the same time. However, with
demand priority, it is possible to implement a scheme in
which certain types of data will be given priority if there
is contention. If the hub or repeater receives two
requests at the same time, the highest priority request
is serviced first. If the two requests are of the same
priority, both requests are serviced by alternating
between the two.
 In a demand-priority network, computers can receive and
transmit at the same time because of the cabling scheme defined
for this access method. In this method, four pairs of wires are
used, which enables quartet signaling, transmitting 25 MHz
signals on each of the pairs of wire in the cable.
51

 Demand priority offers several advantages over
CSMA/CD including:
 The use of four pairs of wires.
 By using four pairs of wires, computers can transmit
and receive at the same time.
 Transmissions through the hub.
 Transmissions are not broadcast to all the other
computers on the network. The computers do not
contend on their own for access to the cable, but
operate under the centralized control of the hub.
Eng.Osama Ghandour
Teacher

Feature or
function
CSMA/CD CSMA/CA Token passing
Demand
priority
Type of
Communicatio
n
Broadcast-
based
Broadcast-
based
Token-based Hub-based
Type of access
method
Contention Contention Noncontention Contention
Type of
network
Ethernet LocalTalk Token Ring
ArcNet
100VG-
AnyLan
Table 3.1 Features of Different Access Methods
53

 Managing data on a network is a form of traffic control.
 The set of rules that governs how network traffic is controlled is
called the access method.
 When using the CSMA/CD access method, a computer waits
until the network is quiet and then transmits its data. If two
computers transmit at the same time, the data will collide and
have to be re-sent. If two data packets collide, both will be
destroyed.
 When using the CSMA/CA access method, a computer transmits
its intent to transmit before actually sending the data.
 When using the token-ring access method, each computer must
wait to receive the token before it can transmit data. Only one
computer at a time can use the token.
 When using the demand-priority access method, each computer
communicates only with a hub. The hub then controls the flow of
data.
Access methods summary
54

Ethernet is a
Network Operating Software
Bus topology
Network access method
Backbone Networks ’element
Eng.Osama Ghandour
Teacher

INCORRECT!!!
Try Again Eng.Osama Ghandour
Teacher

CORRECT
Eng.Osama Ghandour
Teacher

CCNA
Certified Computer Network
Administrator
this Certificate from Cisco company
www.netacade.com
Eng.Osama Ghandour Programming and
electronics Teacher Assiut STEM
School
Exam costs 3000 L.E. in
CISCO centers
But through online
exam is free of charge
58

Eng.Osama Ghandour
Teacher
Closing and summery
Network topologies
HybridBus StarRing
Network OS
AppleShare and Windows
Novel Netware and Windows NT
Client/server
Peer-to-peer
Network access methods
(CSMA/CD) - (CSMA/CA)
Token passing - Demand priority

5 min Reflection
• Mansion one type of each of :
• network topologies
• network OS
• network access methods ?
Eng.Osama Ghandour
Teacher

Home work
provides a summary
comparison between
network types , its OS
and its access data
methods in a tabel . Computer-Networks-
-Introduction_Computer_Networking pdf file Eng.Osama Ghandour
Teacher

Journal Question
 In computer Science (CS.2.08), you
learned about different network
Topologies. What kind of these
network Topologies would you
suggest for a new factory
working in the field of the
industry you are working on for
this semester Capstone? Explain
why you suggested this kind?
62

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Teacher

2020 network topologies and access methods

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