Network
Topology
In computer networking, topology refers to the layout of connected
devices.
In
communication networks, a topology is a usually schematic description of the
arrangement of a network, including its nodes and connecting lines. There are
two ways of defining network geometry: the physical topology and the logical
(or signal) topology.
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| Network Topology Types |
Logical
Topology
Nature of the paths the signals follow from node to node. In many
instances, the logical topology is the same as the physical topology. But this
is not always the case.
Physical
Topology
Actual geometric layout of workstations.
Network
topologies are categorized into the following basic types:
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| Types of Physical Topology |
1. Point-to-Point
Topology
The simplest topology with a permanent link between two endpoints.
Switched point-to-point topologies are the basic model of conventional
telephony. The value of a permanent point-to-point network is unimpeded
communications between the two endpoints.
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| Point-to-Point Topology |
Advantages:
- Lower Cost.
- Easy to setup.
- Good for
temporary network setup.
- Use for
connecting one area to another using a high speed connection.
Disadvantages:
- Limited growth.
- No central
location.
- Weak Security.
2. Ring Topology
In
Ring Topology, all the nodes are connected to each-other in such a way that
they make a closed loop.
A failure in
any cable or device breaks the loop and can shut down the entire network. Every
data packet must pass through all the computers between sender and receiver.
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| Ring Topology |
Advantages:
- Data is quickly
transferred without a ‘bottle neck’ (very fast, all data traffic is in the same
direction).
- The
transmission of data is relatively simple as packets travel in one direction
only.
- Adding
additional nodes has very little impact on bandwidth.
- It prevents
network collisions because of the media access method or architecture required.
Disadvantages:
- The failure of
a single node in the network can cause the entire network to fail.
- The movement or
changes made to network nodes affect the entire network's performance.
- Data sent from
one node to another has to pass through all the intermediate nodes. This makes
the transmission slower in comparison to that in a star topology. The
transmission speed drops with an increase in the number of nodes.
- There is heavy
dependency on the wire connecting the network nodes in the ring.
3. Star Topology
One
of the most common network setups where each of the devices and computers on a
network connect to a central hub. If the central computer fails, the entire
network becomes unusable.
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| Star Topology |
Advantages:
- Good
performance.
- Easy to set up
and to expand. Any non-centralised failure will have very little effect on the
network, whereas on a ring network it would all fail with one fault.
- Adding or
removing network nodes is easy, and can be done without affecting the entire
network.
- Due to the
centralized nature, it is easy to detect faults in the network devices.
- As the analysis
of traffic is easy, the topology poses lesser security risk.
Disadvantages:
- Expensive to
install.
- Extra hardware
required.
- Network
operation depends on the functioning of the central hub. Hence, central hub
failure leads to failure of the entire network.
- Also, the
number of nodes that can be added depends on the capacity of the central hub.
4. Bus Topology
A
bus topology is a type of network setup where each computer and network device
are connected to a single cable or backbone. A bus network is simple and
reliable. If one node fails to operate, all the rest can still communicate with
each other.
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| Bus Topology |
Advantages:
- It is easy to
set up, handle, and implement.
- It is
best-suited for small networks.
- Well suited for
temporary networks (quick setup).
- Initially less
expensive than other topologies.
- Cheap.
Disadvantages:
- The cable
length is limited. This limits the number of network nodes that can be
connected.
- This network
topology can perform well only for a limited number of nodes. When the number
of devices connected to the bus increases, the efficiency decreases.
- It is suitable
for networks with low traffic. High traffic increases load on the bus and the
network efficiency drops.
- It is heavily
dependent on the central bus. A fault in the bus leads to network failure.
- It is not easy
to isolate faults in the network nodes.
- Each device on
the network "sees" all the data being transmitted, thus posing a
security risk.
- Difficult to
administer/troubleshoot.
- Low security.
- Proper
termination is required.(loop must be in closed path).
5. Mesh Topology
A
network setup where each computer and network device is interconnected with one
another, allowing for most transmissions to be distributed, even if one of the
connections go down.
The flow of
information is random and the source to destination path of this information
can take many paths.
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| Mesh Topology |
Advantages:
- The arrangement
of the network nodes is such that it is possible to transmit data from one node
to many other nodes at the same time.
- The failure of
a single node does not cause the entire network to fail as there are alternate
paths for data transmission.
- It can handle
heavy traffic, as there are dedicated paths between any two network nodes.
- Point-to-point
contact between every pair of nodes makes it easy to identify faults.
- Mesh topology isn't affected by size or a shortage of users.
Disadvantages:
- The layout of a
mesh topology requires constant supervision and is very expensive to implement.
- A lot of cabling
is required.
- Owing to its
complexity, the administration of a mesh network is difficult.
6. Tree Topology
A
tree topology is a type of network topology that includes at least three
specific levels in a topology hierarchy.
Experts may
define a tree topology as a combination of star and bus topology, where
multiple elements are connected through a single lateral connection.
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| Tree Topology |
Advantages:
- Experts may
define a tree topology as a combination of star and bus topology, where
multiple elements are connected through a single lateral connection.
- Expansion of
Network is possible and easy.
- Error detection
and correction is easy.
- Each segment is
provided with dedicated point-to-point wiring to the central hub.
- If one segment
is damaged, other segments are not affected.
- The advantages
of centralization that are achieved in a star topology are inherited by the
individual star segments in a tree network.
Disadvantages:
- Because of its
basic structure, tree topology, relies heavily on the main bus cable, if it
breaks whole network is crippled.
- Owing to its
size and complexity, maintenance is not easy and costs are high. Also,
configuration is difficult in comparison to that in other topologies.
- Though it is
scalable, the number of nodes that can be added depends on the capacity of the
central bus and on the cable type.
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