What is a network topology? 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.
The Physical Topology...
The physical layout of devices on a network. Every
LAN has
a
topology, or the
way that the devices on a network are arranged and how they communicate with
each other. The way that the
workstations are
connected to the network through the actual cables that transmit data -- the
physical structure of the network -- is called the physical topology. The
logical topology,
in contrast, is the way that the signals act on the network media, or the way
that the data passes through the network from one device to the next without
regard to the physical interconnection of the devices.
The Logical Topology...
Also called
signal topology. Every
LAN has
a
topology, or the
way that the devices on a network are arranged and how they communicate with
each other. The way that the
workstations are
connected to the network through the actual cables that transmit data -- the
physical structure of the network -- is called the
physical topology.
The logical topology, in contrast, is the way that the signals act on the
network media, or the way that the data passes through the network from one
device to the next without regard to the physical interconnection of the
devices.
Logical topologies are bound to the network
protocols that direct
how the data moves across a network. The
Ethernet protocol is a
common logical bus topology protocol.
LocalTalk is a common
logical bus or
star
topology protocol. IBM's
Token Ring
is a common logical ring topology protocol.
Types of Network Topologies
Bus Topology: In this type of network topology, all
the nodes of a
network are connected to a common transmission medium having two
endpoints. All the data that travels over the network is transmitted
through a common transmission medium known as
the bus or the backbone of
the network. When the transmission medium has exactly two endpoints,
the network topology is known by the name, 'linear bus topology'. In
case the transmission medium, also
called the network backbone, has more
than two endpoints, the network is said to have a distributed
bus
topology. Bus topology is easy to handle and implement and is best
suited for small networks. But the downside of this topology is that the
limited cable length limits the number of stations, thus limiting the
performance to a less number of nodes.
Ring Topology: In a ring topology, every node in the network is
connected to two other nodes and the first and the last nodes are
connected to each other. The data that are transmitted over the network
pass through each of the nodes in the ring until they reach the
destination node. In a ring network, the data and the signals that pass
over the network travel in a single direction. The dual ring topology
varies in having two connections between each of the network nodes. The
data flow along two directions in the two rings formed thereby. The ring
topology does not require a central server to manage connectivity
between the nodes and facilitates an orderly network operation. But, the
failure of a single station in the network can render the entire
network inoperable. Changes and moves in the stations forming the
network affect the network operation.
Mesh Topology: In a full mesh network, each network node is
connected to every other node in the network. Due to this arrangement of
nodes, it becomes possible for a simultaneous transmission of signals
from one node to several other nodes. In a partially connected mesh
network, only some of the network nodes are connected to more than one
node. This is beneficial over a fully connected mesh in terms of
redundancy caused by the point-to-point links between all the nodes. The
nodes of a mesh network require possessing some kind of routing logic
so that the signals and the data traveling over the network take the
shortest path during each of the transmissions.
Star Topology: In this type of network topology, each node of the
network is connected to a central node, which is known as a hub. The
data that is transmitted between the network nodes passes across the
central hub. A distributed star is formed by the interconnection of two
or more individual star networks. The centralized nature of a star
network provides a certain amount of simplicity while also achieving
isolation of each device in the network. However, the disadvantage of a
star topology is that the network transmission is largely dependent on
the central hub. The failure of the central hub results renders the
entire network inoperable.
Tree Topology: It is also known as a hierarchical topology and
has a central root node that is connected to one or more nodes of a
lower hierarchy. In a symmetrical hierarchy, each node in the network
has a specific fixed number of nodes connected to those at a lower
level.
