Physical Topology:--
The term physical topology refers to the way in which a network is laid out physically..
Two or more device connect (0 a link, two or more links form a topology. The topology--
1.)Mesh:- In a mesh topology, every device has a dedicated point-to-point link to every
other device. The term dedicated means that the link carries traffic only between the
two devices it connects.
for n nodes-we need
n(n—l)/2
duplex-mode links.
*advantages over other network topologies.:---
1.)It uses dedicated links so guarantees that each connection can carry its own data load,so eliminating the traffic problems.
2.)a mesh topology is robust. If one link becomes unusable, it does not incapacitate the entire system.
3.)privacy or security. When every
message travels along a dedicated line, only the intended recipient sees it.
4.)fault identification and fault isolation is easy.
*disadvantage:-
1)the amount of cabling and the
number of i/o ports required.
2.) the hardware required to connect each link (I/O ports and cable) can be
prohibitively expensive. For these reasons a mesh topology is usually implemented in a
limited fashion.
2.)Star Topology :-In a star topology, each device has a dedicated point-to-point link
only to a central controller, usually called a huh. Thc devices arc not directly linked to
one another. Unlike a mesh topology, a star topology does not allow direct traffic
between devices. The controller acts as an exchange: If one device wants to send data to
another, it sends the data to the controller, which then relays the data to the other connected device .
advantage:-1.)A star topology is less expensive than a mesh topology. In a star, each device needs
only one link and one I/O port to connect it to any number of others.
2)it easy to install and reconfigure.
3.)robustness
4.)If one link fails, only that link is affected. All
other links remain active.so easy fault identification and fault isolation.
disadvantage:-
1.)dependency of the whole topology
on one single point, the huh. If the huh goes down, the whole system is dead.
2.)star requires far less cable than a mesh, each node must be linked to a
central hub. For this reason. often more cabling is required in a star.
3.) Bus Topology :-The preceding examples all describe point-to--point connections. A bus
topology, on the other hand, is multi-point. One long cable acts as a backbone to link all
the devices in a network.
Nodes are connected to the bus cable by drop lines and taps.
Advantages:-
1.) easy of installation.
2.)Due to Backbone , bus uses less cabling than mesh or star topologies. In a star, for
example, four network devices in the same room require four lengths of cable .
Disadvantages :-1.) difficult reconnection and fault isolation.
2.)difficult to add new
devices.
3.)Signal reflection at the taps can cause degradation . This degradation
can be controlled by limiting the number and spacing of devices connected to a given
length of cable.Adding new devices may therefore require modification or replacement
of the backbone.
4.)fault or break in the bus cable stops all Transmission.The damaged area reflects signals back in the
direction of origin, creating noise in both directions.
4.)Ring Topology-- In a ring topology, each device has a dedicated point-to-point connection
with only the two devices on either side of it. A signal is passed along the ring
in one direction, from device to device, until it reaches its destination. Each device in
the ring incorporates a repeater. When a device receives a signal intended for another
device, its repeater regenerates the bits and passes them along.
adv-A ring is relatively easy to install and reconfigure.To add or delete a device requires
changing only two connections.a signal is circulating at all times. If one device does not
receive a signal within a specified period, it can issue an alarm. The alarm alerts the
network operator to the problem and its location.
disad-unidirectional traffic can be a disadvantage.a break in
the ring (such as a disabled station) can disable the entire network. This
The term physical topology refers to the way in which a network is laid out physically..
Two or more device connect (0 a link, two or more links form a topology. The topology--
1.)Mesh:- In a mesh topology, every device has a dedicated point-to-point link to every
other device. The term dedicated means that the link carries traffic only between the
two devices it connects.
for n nodes-we need
n(n—l)/2
duplex-mode links.
*advantages over other network topologies.:---
1.)It uses dedicated links so guarantees that each connection can carry its own data load,so eliminating the traffic problems.
2.)a mesh topology is robust. If one link becomes unusable, it does not incapacitate the entire system.
3.)privacy or security. When every
message travels along a dedicated line, only the intended recipient sees it.
4.)fault identification and fault isolation is easy.
*disadvantage:-
1)the amount of cabling and the
number of i/o ports required.
2.) the hardware required to connect each link (I/O ports and cable) can be
prohibitively expensive. For these reasons a mesh topology is usually implemented in a
limited fashion.
2.)Star Topology :-In a star topology, each device has a dedicated point-to-point link
only to a central controller, usually called a huh. Thc devices arc not directly linked to
one another. Unlike a mesh topology, a star topology does not allow direct traffic
between devices. The controller acts as an exchange: If one device wants to send data to
another, it sends the data to the controller, which then relays the data to the other connected device .
advantage:-1.)A star topology is less expensive than a mesh topology. In a star, each device needs
only one link and one I/O port to connect it to any number of others.
2)it easy to install and reconfigure.
3.)robustness
4.)If one link fails, only that link is affected. All
other links remain active.so easy fault identification and fault isolation.
disadvantage:-
1.)dependency of the whole topology
on one single point, the huh. If the huh goes down, the whole system is dead.
2.)star requires far less cable than a mesh, each node must be linked to a
central hub. For this reason. often more cabling is required in a star.
3.) Bus Topology :-The preceding examples all describe point-to--point connections. A bus
topology, on the other hand, is multi-point. One long cable acts as a backbone to link all
the devices in a network.
Nodes are connected to the bus cable by drop lines and taps.
Advantages:-
1.) easy of installation.
2.)Due to Backbone , bus uses less cabling than mesh or star topologies. In a star, for
example, four network devices in the same room require four lengths of cable .
Disadvantages :-1.) difficult reconnection and fault isolation.
2.)difficult to add new
devices.
3.)Signal reflection at the taps can cause degradation . This degradation
can be controlled by limiting the number and spacing of devices connected to a given
length of cable.Adding new devices may therefore require modification or replacement
of the backbone.
4.)fault or break in the bus cable stops all Transmission.The damaged area reflects signals back in the
direction of origin, creating noise in both directions.
4.)Ring Topology-- In a ring topology, each device has a dedicated point-to-point connection
with only the two devices on either side of it. A signal is passed along the ring
in one direction, from device to device, until it reaches its destination. Each device in
the ring incorporates a repeater. When a device receives a signal intended for another
device, its repeater regenerates the bits and passes them along.
adv-A ring is relatively easy to install and reconfigure.To add or delete a device requires
changing only two connections.a signal is circulating at all times. If one device does not
receive a signal within a specified period, it can issue an alarm. The alarm alerts the
network operator to the problem and its location.
disad-unidirectional traffic can be a disadvantage.a break in
the ring (such as a disabled station) can disable the entire network. This
No comments:
Post a Comment