it is such a good slide with good explanation

1. Bugema University
DNCT062 Network Principles
Lecture 3
1

2. NETWORK
TOPOLOGY.
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3. Two Types of Network
Topologies
Physical topology is the
physical layout of the
components on the
network
Logical topology determines how the
hosts access the medium to
communicate across the network
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4. PHYSICAL NETWORK TOPOLOGY.
• In networking, the term "topology" refers to
the layout of connected devices on a network.
• The physical layout & configuration of
computers, cables, nodes, and other peripherals
on a Network is generally referred to as the
physical Network topology.
• Network topology may also be logical and this
generally refers to the protocols used on the
Network.
Note: (Protocols are to be discussed later)
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5. Physical Network Topology cont’d.
• So, Network topology is the study of the
arrangement or mapping of the elements
(links, nodes, etc.) of a network, especially
the physical (real) and logical (virtual)
interconnections between nodes.
• OR: A Network Topology is the
arrangement with which computer systems
or network devices are connected to each
other
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6. Network Topology cont’d.
• Topologies are the most important part of
the network design theory.
• A better network can be built if you
have the knowledge of these topologies
and if you know the difference between
them.
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7. Common network Topologies.
• Point-to-Point
• Star
• Bus
• Mesh
• Ring
• Tree
Etc
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8. 1) Point-to-point
• The simplest topology is a permanent link
between two endpoints.
• Point-to-point networks contains exactly
two hosts such as computer, switches or
routers, servers connected back to back
using a single piece of cable. Often, the
receiving end of one host is connected to
sending end of the other and vice-versa.
• Like
– A microphone to a single public address
speaker.
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9. The Point-to-Point topology
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10. 2) Star Topology
• The Star topology involves each node on the
computer network is directly connected to the
central Hub or concentrator as shown in the next
slide.
• Each of the nodes of the network is connected to a
central node with a point-to-point link.
• The hub device can be any of the following:
➢Layer-1 device such as hub or repeater
➢Layer-2 device such as switch or bridge
➢Layer-3 device such as router or gateway
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11. The Star Topology.
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12. Characteristics of the Star Topology
• Note: These explain the advantages
and disadvantages of the Star
Topology as given in the next slides
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13. Advantages of the Star Topology
• Easy to install, implement and extend (in the
event of Network expansion).
• The failure of one node does not have a
major effect on the functionality of the
others.
• No problems with collisions of data
since each node has its own cable to the
server / hub.
• Security can be implemented in the
concentrator for all.
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14. Advantages Cont’d
• It is easy to modify and add new
computers to the star network without
disrupting the rest of the nodes.
• Network faults can easily be identified
centrally and parts are easy to remove.
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15. Disadvantages of a Star Topology.
●Requires more cable length than a
linear topology.
●If the hub or concentrator fails, the
entire network may fail.
●More expensive than linear bus
topologies since it involves purchase
of additional hardware – the
concentrator.
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16. 3) The Bus Topology
• The Bus Topology involves the use of one Linear
Backbone cable with a terminator at each end, to
which all the nodes / computers are connected.
• It is one of the simple forms of networking where a
failure of a device does not affect the other devices.
• But failure of the shared communication line can make
all other devices stop functioning.
• A bus can be
– Linear Bus
– Distributed bus
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17. The Bus Topology cont’d
a) Linear bus:
• All the nodes of the network are
connected to a common transmission
medium which has exactly two
endpoints .
• The two endpoints are normally
terminated with a device called a
terminator.
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18. The Bus Topology cont’d
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19. The Bus Topology cont’d
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Both ends of the shared channel have line terminator. The data is
sent in only one direction and as soon as it reaches the extreme end,
the terminator removes the data from the line.

20. The Bus Topology cont’d
b) Distributed bus:
• The type of network topology in
which all of the nodes of the network
are connected to a common
transmission medium which has
more than two endpoints
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22. Characteristics of the Bus Topology
These define the advantages and
disadvantages.
Advantages.
• Cheap (probably the cheapest topology to
install).
• Easy to implement.
• Less cable length required.
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23. Disadvantages of the Bus Topology.
• Difficult to identify the source of a problem in
case of network failure.
• Limited cable length and number of stations.
• A break of the main cable means a break of the
entire network.
• Performance may degrade as the network
expands
• Low security (all computers on the bus can see all
data transmissions).
• Terminators are required at both ends of the
backbone cable. Proper termination is required.
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24. 4) Ring Topology.
• A ring Topology is one where each node is
connected to two other nodes with the first
and last being connected to each other to
form a ring-like structure (Circular
network structure).
• When one host tries to communicate or
send message to a host which is not
adjacent to it, the data travels through all
intermediate hosts. To connect one more
host in the existing structure, the
administrator may need only one more
extra cable.
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25. Ring Topology cont’d.
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26. Ring Topology cont’d.
• It uses a token ring to carry data from
the source to the destination: Data is sent
from one machine to the next around the
ring until it reaches its destination then
back to the origin.
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27. Characteristics of the Ring Topology
Advantages and disadvantages define them.
Advantages:
• Data transmission is relatively simple since
data moves in one direction.
• Logically, a token passes from one computer
to another so equal attention is given to all
nodes.
• Reliable and easier to manage.
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28. Disadvantages of the Ring Topology Cont’d
• Difficult to troubleshoot.
• Difficult to add or remove a computer.
• A failure on one computer / node may
cause disruption in the entire Network
since the Token can’t be passed on.
• Before the data reaches the destination, it
must travel through all the nodes before
it.
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29. 5) Mesh Topology
• A Mesh Topology involves all the nodes
on the network being interconnected to
one another.
• It is a network topology that resembles a
wire mesh and involve the concept of
routes.
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30. a) Partial Mesh Topology
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31. b) Full Mesh topology
A mesh network in which every device
connects to every other is called a full mesh.
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32. • The main advantage of this continuous
connection between the nodes (Full Mesh
Topology) is that when one node goes
down, the others remain unaffected.
• However, implementing such a network
is relatively expensive and difficult.
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33. 6. Tree Topology
• Also known as Hierarchical Topology, this is the
most common form of network topology in use
presently.
• This topology imitates as extended Star topology
and inherits properties of bus topology.
• That is: Tree topologies integrate multiple star
topologies together onto a bus.
• In its simplest form, only hub devices connect
directly to the tree bus and each hub functions
as the "root" of a tree of devices.
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34. Tree Topology Cont’d
• This topology divides the network in to multiple
levels/layers of network. Mainly in LANs, a network is
bifurcated into three types of network devices
• The lowermost is access-layer where computers are
attached.
• The middle layer is known as distribution layer, which
works as mediator between upper layer and lower
layer.
• The highest layer is known as core layer, and is
central point of the network, i.e. root of the tree from
which all nodes fork.
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35. Tree Topology Layers
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36. Tree Topology Cont’d
• All neighboring hosts have point-to-point
connection between them.
• Similar to the Bus topology, if the root goes
down, then the entire network suffers even.
• though it is not the single point of failure.
• Every connection serves as point of failure,
failing of which divides the network into
unreachable segment.
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37. Tree Topology
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38. Advantages of a Tree Topology
• Point-to-point wiring for individual
segments.
• Supported by several hardware and
software venders.
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39. Disadvantages of a Tree Topology
• Overall length of each segment is limited
by the type of cabling used.
• If the backbone line breaks, the entire
segment goes down.
• More difficult to configure and wire than
other topologies.
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40. 7. Hybrid network topologies
• The hybrid topology is a type of network
topology that is composed of one or more
interconnections of two or more networks
that are based upon different physical
topologies
• Hybrid topology inherits merits and
demerits of all the incorporating
topologies.
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41. The Hybrid topology
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42. 8. Daisy Chain topology
• This topology connects all the hosts in a linear
fashion.
• Similar to Ring topology, all hosts are connected
to two hosts only, except the end hosts.
• Means, if the end hosts in daisy chain are
connected then it represents Ring topology
• Each link in daisy chain topology represents single
point of failure. Every link failure splits the
network into two segments.
• Every intermediate host works as relay for its
immediate hosts.
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43. The Daisy Chain Topology
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44. Considerations when Choosing a
Topology.
• Funds. A linear bus network may be the
least expensive way to install a network
i.e no concentrators are required.
• Length of cable needed. The linear bus
network uses shorter lengths of cable.
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45. Considerations when Choosing a
Topology Cont’d.
• Future growth. With a star topology,
expanding a network is easily done by
adding another concentrator.
• Cable type. The most common cable in
use is unshielded twisted pair, which is
most often used with star topologies.
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46. Logical Topologies
• A logical topology is a concept in networking that defines the
architecture of the communication mechanism for all nodes in a
network.
• Using network equipment such as routers and switches, the
logical topology of a network can be dynamically maintained and
reconfigured
• The logical topology defines how the data should transfer.
• Contrast this to the physical topology, which consists of the
layout of cables, network devices and wiring.
The two most common types of logical topologies are:
▪ broadcast
▪ and token passing.
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47. broadcast /Bus topology
• There is no order that the hosts must follow to
use the network
• – it is first come, first served for transmitting
data on the network.
• Ethernet uses the logical bus topology to transfer
data.
• Under a bus topology a node broadcasts the data
to the entire network.
• All other nodes on the network hear the data and
check if the data is intended for them.
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48. Token passing / Ring Topology
• In this topology, only one node can be allowed to
transfer the data in a network at a given time.
• If the host has no data to send, it passes the token
to the next host and the process repeats itself.
• This controls network access by passing an
electronic token sequentially to each host.
• The node having token only can transmit the data
in a network and hence the collision can be
avoided in a network.
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49. End of the Lecture
Thanks
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