Time
3 hours 38 minutes
Difficulty
Beginner
CEU/CPE
2

Video Description

A computer network topology is the arrangement and/or structure of the various elements of a computer network that depicts both physically and logically. In this lesson you will learn about the five basic network topologies along with their advantages and disadvantages. Computer Network Topology- Physical Topology: the physical way the network is wired

  • How computers connected to each other
  • Logical Topology: the way messages are sent

    • How to send a message from machine to another

Basic Network Topologies- Point-to-point

  • Connection between two machines through a dedicated media link
  • Cable link or a wireless link
  • Bus

    • Single cable functions as a shared communication media bus (Backbone)
    • Computers attach or tap with an interface connector
    • Terminators at each end of the cable

      • Connected with a Y-piece or T-piece
    • Advantages

      • Simple to design
      • Easy to install
      • Inexpensive due to using

        • Coaxial cable
        • BNC Connectors
    • Disadvantages

      • Less security

        • Allows sniffing

          - Every message passing from one machine to the other can be sniffed by any other machine on the bus
          
      • Slow during high traffic

        • If high traffic is introduced the speed of the whole network goes down leading to poor performance
      • Lead to collisions
  • Ring

    • Cable connects and node to another to form a ring
    • Messages travel through the ring always in the same direction
    • Data messages are transmitted in frames that circulate all the machines which allows for sniffing
    • Sent frame circulates back to source of the message to acknowledge transmission has been done and to set a frame free for another message
    • Advantages - similar to the Bus Topology

      • Simple to design
      • Easy to install
      • Inexpensive due to using

        • Coaxial cable
        • BNC Connectors
    • Disadvantages

      • The entire network fails if one machine fails
      • Expansion or reconfiguration affects operation

        • You have to break the ring in order to expand or configure
      • Slow for big number of machines
  • Star

    • Each station is connected directly to a central device
    • The connection is like a number of point-to-point links
    • Central devices is Hub or Switch
    • Switch is more recent technology and more secure device than hub

      • Switch does not allow sniffing
      • Hub allows sniffing
    • Advantages

      • Network not affected if one machine fails
      • Network expansion and reconfiguration is simple
      • Troubleshooting is easy
    • Disadvantages

      • If the central device fails all the network fails
  • Mesh

    • Connect all devices with multiple paths

      • Every device is connected to the other devices through a separate link
    • Offers a very high redundancy

      • Very high reliability
    • N=n*(n-1)/2

      • N= number of cables
      • n= number of connected nodes
      • This equation is used to calculate the number of cables used in any Mesh Topology to know the number of connected nodes
    • Advantages

      • Faults tolerant

        • Allows broken cables to exist without breaking the whole topology
      • Secure (High availability)
    • Disadvantages

      • Expensive due to redundancy

Video Transcription

00:00
Now let us explore the computer networks. Apologies.
00:05
What is a computer network? Topology? What is meant by the word apology?
00:10
The word apology means the arrangement, the structure of the various elements off a computer network, which depicts both physically and logically.
00:20
The physical topology is the physical way the network is wired, how the computers are connected to each other.
00:27
The logical topology identifies the way messages are sent, how to send a message and how a message moves from one machine to another.
00:38
That apology can be explained in a physical and logical essences.
00:45
The basic network apologies the most common. The most well known apologies are
00:50
the point. The point topology, the bust apology, the ring topology, the start apology and the mashed apology.
00:58
Now we will explore one by one off them.
01:03
The point upon topology is just a link,
01:07
a physical link, either a cable or a wireless thing that is connecting two points. Or it can be a logical link, logical point to point connection
01:19
that is passing through an eyes Be Internet service provider connecting a source No to a destination. Note.
01:26
It's a dedicated link,
01:30
a dedicated media tow. Connect these two nodes. Only.
01:34
The bust apology
01:37
is a single cable that functions as a bus
01:41
as a shared media as a backbone.
01:44
Computers attached or tap with an interface connected to this bus.
01:49
This bus this shared media
01:53
Easter belated by Terminators
01:57
and the computers are connected through connectors either in T peace or in y peas. We can see here
02:07
that apology off the connection and the connectors, the Teepees, the Wye Peace and the Terminator that resides at the end off the must scape,
02:20
the advantage is off the bust. Apology is that it is simple to design, very simple to design and very easy to install.
02:28
It is also inexpensive due to using the co exhale cables as the shared media
02:35
and using the B and C connectors
02:38
boy in it
02:38
nil concealment, connectors.
02:42
These type of connectors are very cheap,
02:45
inexpensive
02:46
and very efficient in working
02:49
that this advantage is off. This must apology is
02:53
the security.
02:54
This the apology allows for sniffing
02:58
every message. Passing from one machine to another can be sniffed by any other machine on the same bus.
03:06
This means that the privacy of the message, the confidentiality of the message can be
03:12
tackled any time it's passing the media.
03:16
The bust apology is slow during high traffic.
03:22
If high traffic is introduced to this topology,
03:25
the speed off the whole network goes down,
03:30
leading to poor performance.
03:32
The most apology allows for collisions.
03:37
Collisions means that
03:38
assume that two machines are sending their messages at the same second.
03:46
Both off messages will exist on the shared media at the same second as well,
03:52
so both messages will collide with each other.
03:55
Here is how collision happens.
03:59
Zeros and ones off. Both messages will no longer be zeros and ones. They will be something else that is called jam signals,
04:08
something that is
04:10
that has no meaning.
04:12
That is meaningless,
04:14
which means that we have to retransmit
04:17
both messages again,
04:20
which means poor performance and slower network and many times off retransmission.
04:29
The second, the third apology, is the ring to Polish
04:32
drink. Apology, basically is a cable in the form of a ring, as shown,
04:39
that connects one Noto, another toe, another to form a rink.
04:45
The ends are attached to each other in the form of a ring.
04:49
Messages travelled through this ring, always in the same direction,
04:56
always in one direction, either clockwise or anti clockwise.
05:00
The messages are transmitted in frames
05:03
that circulates all the machines, which allows for sniffing.
05:10
Obviously,
05:13
the ring topology allows for acknowledgement.
05:15
The sun frames circulates back to the source
05:19
of the message
05:20
toe, acknowledge that transmission has been done
05:25
and to set
05:27
the frame free for another machine
05:30
toe put its message on the same frame
05:34
to be sent as well.
05:38
The advantage is off. Drink apology is that it is simple. Also designed to design,
05:44
easy to install.
05:46
It's very inexpensive due to using the co axial cables and the B and C connectors.
05:53
It's
05:55
it looks like
05:57
the bust apology
06:00
in this site.
06:01
This advantage is off the rink. Apology is that the entire network fails. If only one machine fails. Because it breaks the ring,
06:11
it stops the messages from circulation.
06:14
So the whole network rail's. If only one machine
06:19
member of this network fails to connect
06:24
the expansion off this network or reconfiguration effects operation, imagine that you want to expand this network. You have to stop one of the machines, add another machine,
06:35
you will have to break the rink, and the circulation off messages will stop for some time until you finish the expansion or reconfiguration, then the operation is restored.
06:49
Drink apologies also slow for big numbers off machines.
06:56
If a big number off machine is Ace told interlinked apology, this leads to slow network and poor performance. Also
07:05
the start apology. This is the most well known the most common topology that issues nowadays. In that works.
07:15
The start apology depends on connecting each station directly to a central device as seen in the edge.
07:24
The connection is like a number off point to point links. Each machine
07:29
looks like being connected in a point to point link. Tow this central device.
07:34
This central device can be a hub order switch
07:39
Nowadays, switches arm or commonly used than hops.
07:44
The switch is a more recent technology and more secure device.
07:48
The switch
07:49
allows for no sniffing to be done,
07:54
while the hub allows for sniffing to be done on the natural.
07:59
The switch allows for no collision
08:01
to take place while they have allows for collisions to take place.
08:07
So the switches, now
08:09
that most used technologies in collect in connecting
08:15
a number of machines to each other in a local area network or Ln
08:20
The advantage is off the store topology is that the network is not affected if one machine fails or if the network is reconfigured.
08:31
The network expansion
08:33
is very simple. You just add the new machine,
08:37
so the switch or the hub without affecting the performers or the operation off the whole letter.
08:45
Troubleshooting is easy. You can easily identify the failing machine from the switch.
08:52
You can easily identify where the problem or where the broken cable exists.
08:58
The disadvantage is off. The start apology is that if the central device fails, all the network fails,
09:05
and this is very rare toe happen. This is not common toe happen.
09:09
Central devices are so far reliable.
09:16
The mashed apology means that every device is connected to the other devices through a separate link.
09:24
It connects all devices with multiple partners.
09:28
So
09:30
between
09:31
each device and another, you can find
09:35
multiple partners that can connect such device to the other one.
09:39
It offers a very high redundancy in connection, which means very high reliability, which is part off the security off the network.
09:50
The number of cables equals tow the number off connected nodes
09:54
multiplied by the same number, minus one and then divided by two. This equation is used to calculate the number of cables used in any meshed apology. Knowing the number off connected notes,
10:09
the advantage is off. The matched apology is that it is very high, full tolerant.
10:16
It allows for broken cables to exist because any broken cable can be substituted with another path for
10:24
a good cable to exist.
10:26
It's very secure, since it has high availability and availability. It's part of the security,
10:33
so it is very secure. From this point of view,
10:35
the disadvantage is off. The mashed apology is that it is expensive you to using hot,
10:43
big number off cables
10:46
and you too, offering high redundancy. This leads to very high coast. Sometimes
10:52
by this we come to the end off the computer networks. Apologies. And we hope that we clarified the most
11:01
known and common basic computer network. Apologies. Thank you

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Instructed By

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Mohammad Adly
EC3 Manager at Information Technology Institute
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