physical / network topology:

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Physical / Network Topology:

The term physical topology refers to the way in which a network is laid out physically

1\o or more devices connect to a link; two or more links form a topology.

The topology of a network is the geometric representation of the relationship of all the

links and linking devices (usually called nodes) to one another.

There are many basic topologies possible:

1. Fully connected 2. Bus topology 3. Star topology

4. Ring topology 5. Tree topology 6. Mesh topology

7. Hybrid topology 8. Dual Ring topologies 9. Linear-topologies


Classification of network topologies:

There are also two basic categories of network topologies:

1. Physical topologies

Physical topology is the mapping of the nodes of a network and the physical connections

between them–the layout of wiring, cables, the locations of nodes, and the

interconnections between the nodes and the cabling or wiring system.

2. Logical topologies

Logical topology 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.

1. Mesh:

In a mesh topology, every device has a dedicated point-to-point link to every device. The

term dedicated means that the link carries traffic only between the two devices it

connects.

The main disadvantages of a mesh are related to the amount of cabling and the number

of I/O ports required.

For these reasons a mesh topology is usually implemented in a limited fashion:

First, because every device must be connected to every other device, installation and

reconnection are difficult.

Second, the sheer bulk of the wiring can be greater than the available space (in walls,

ceilings, or floors) can accommodate.

Finally, the hardware required to connect each link (I/O ports and cable) can be

prohibitively expensive.


2. Star Topology

In a star topology, each device has a dedicated point-to-point link only to a central

controller, usually called a hub. The devices are 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.

Advantages:

1. A star topology is less expensive than a mesh topology.

2. In a star, each device needs only one link and one I/O port to connect it to any

number of others. This factor also makes it easy to install and reconfigure.

One big Disadvantage of a star topology is the dependency of the whole topology on

one single point, the hub. If the hub goes down, the whole system is dead.

** Although a star requires far less cable than a mesh, each node must be linked to

central hub.

For this reason, often more cabling is required in a star than in some

other topologies (such as ring or bus).


The star topology is used in local-area networks (LANs)

3. Bus Topology:

A bus topology, on the other hand, is multipoint. 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.

* A drop line is a connection running between the device and the main cable.

* A tap is a connector that either splices into the main cable or punctures the

sheathing of a cable to create a contact with the metallic core.

**As a signal travels along the backbone, some of its energy is transformed into heat.

Therefore, it becomes weaker and weaker as it travels farther and farther. For this

reason there is a limit on the number of taps a bus can support and on the

distance between those taps.


Advantages: of a bus topology include ease of installation. a bus uses less cabling than

mesh or star topologies

Disadvantages:

1. Include difficult reconnection and fault isolation.

2. It can therefore be difficult to add new devices.

3. Signal reflection at the taps can cause degradation in quality.

Adding new devices may therefore require modification or replacement of the

backbone.

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.


Advantage:

1. A ring is relatively easy to install and reconfigure.

2. Each device is linked to only its immediate neighbors.

3. To add or delete a device requires changing only two connections.

4. In addition, fault isolation is simplified.

In a simple ring, a break in the ring (such as a disabled station) can disable the entire

network. This weakness can be solved by using a dual ring or a switch capable of closing

off the break.

5. Hybrid Topology:

A network can be hybrid. For example, we can have a main star topology with each

branch connecting several stations in a bus topology as shown in coming Figure.


6. Tree Topology:

A tree topology combines characteristics of linear bus and star topologies. It consists of

groups of star-configured workstations connected to a linear bus backbone cable. Tree

topologies allow for the expansion of an existing network, and enable schools to

configure a network to meet their needs.

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Phvs I / Network Topolosy:

The term phvsical topoloey refers to the way in which a network is laid out physically

1\o or more devices connect to a link; two or more links form a topology.

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The topology of a network is the geometric representation of the relationship of all the

links and linking devices (usually called nodes) to one another.

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There are

1. Fully connected 2. Bus topology 3. Star topology

4. Ring topology 5. Tree topology 6. Mesh topology

7. Hybrid topology 8. Dual Ring topologies 9. Linear-topologies

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Classification of network topolosies:


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Physical topology is the mapping of the nodes of a network and the physical connections

between them-the layout of wiring, cables, the locations of nodes, and the

interconnections between the nodes and the cabling or wiring system.

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2. Logical topologies

Logical topology is the way that the signals act on the network media, or the way that

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physical interconnection of the devices.

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1. Mesh:

In a mesh topology, every device has a dedicated point-to-point link to every device. The

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.The main disadvantages of a mesh are related to the amount of cabling and the numberof I/O ports required.

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2. Star Topology

In a star topology, each device has a dedicated point-to-point link only to a central

controller, usually called a hub. The devices are not directly tinked to one another. Unlikea 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 rerays the data to the other connected

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2. In a star, each device needs only one link and one I/O port to connect it to any

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3. Bus Topology:

A bus topology, on the other hand, is multipoint. One long cable acts as a backbone to

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4. Ring Topology

In a ring topology, each device has a dedicated point-to-point connection with only the

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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

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In a simple ring, a break in the ring (such as a disabled station) can disable the entirenetwork. This weakness can be solved by using a dual ring or a switch capable of closingoff the break.

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5. Hybrid Topology:

A network can be hybrid. For example, we can have a main star topology with eaoh

branch connecting several stations in a bus topology as shown in coming Figure.

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6. Tree Topology:

A tree topology combines characteristics of linear bus and star topologies. It consists ofgroups of star-configured workstations connected to a linear bus backbone cable. Tree

topologies allow for the expansion of an existing network, and enable schools toconfigure a network to meet their needs. , . ./

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Physical / Network Topology:

The term physical topology refers to the way in which a network is laid out physically1\o or more devices connect to a link; two or more links form a topology.The topology of a network is the geometric representation of the relationship of all the links and linking devices (usually called nodes) to one another.

1

There are many basic topologies possible: 1. Fully connected 2. Bus topology 3. Star topology4. Ring topology 5. Tree topology 6. Mesh topology7. Hybrid topology 8. Dual Ring topologies 9. Linear-topologies

Classification of network topologies:


1. Physical topologiesPhysical topology is the mapping of the nodes of a network and the physical connections between them–the layout of wiring, cables, the locations of nodes, and the interconnections between the nodes and the cabling or wiring system.

2. Logical topologiesLogical topology 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.

1. Mesh:

In a mesh topology, every device has a dedicated point-to-point link to every device. The term dedicated means that the link carries traffic only between the two devices it connects.The main disadvantages of a mesh are related to the amount of cabling and the number of I/O ports required.

For these reasons a mesh topology is usually implemented in a limited fashion:First, because every device must be connected to every other device, installation andreconnection are difficult.Second, the sheer bulk of the wiring can be greater than the available space (in walls, ceilings, or floors)

can accommodate.Finally, the hardware required to connect each link (I/O ports and cable) can be prohibitively expensive.

2. Star Topology :

In a star topology, each device has a dedicated point-to-point link only to a central controller, usually called ahub. The devices are not directly linked to one another.Unlike a mesh topology, a star topology does not allowdirect traffic between devices. The controller acts as anexchange: If one device wants to send data to another,it sends the data to the controller, which then relaysthe data to the other connectedDevice.

Advantages: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 ofothers. This factor also makes it easy to install and reconfigure.

One big Disadvantage of a star topology is the dependency of the whole topology on onesingle point, the hub. If the hub goes down, the whole system is dead.** Although a star requires far less cable than a mesh, each node must be linked tocentral hub.

For this reason, often more cabling is required in a star than in some other topologies(such as ring or bus).The star topology is used in local-area networks (LANs)

6

3. Bus Topology:

A bus topology, on the other hand, is multipoint. One long cable acts as a backbone tolink all the devices in a network.Nodes are connected to the bus cable by drop lines and taps

• A drop line is a connection running between the device and the main cable.

• A tap is a connector that either splices into the main cable or punctures thesheathing of a cable to create a contact with the metallic core

**As a signal travels along the backbone, some of its energy is transformed into heat.Therefore, it becomes weaker and weaker as it travels farther and farther. For this reasonthere is a limit on the number of taps a bus can support and on the distance betweenthose taps.

Advantages: of a bus topology include ease ofinstallation. a bus uses less cabling than mesh orstar topologies

Disadvantages:1.Include difficult reconnection and fault isolation.2. It can therefore be difficult to add new devices.3.Signal reflection at the taps can causedegradation in quality.4.Adding new devices may therefore requiremodification or replacement of the backbone

4. Ring Topology:

In a ring topology, each device has a dedicated point-to-point connection with only thetwo devices on either side of it. A signal is passed along the ring in one direction, fromdevice to device, until it reaches its destination. Each device in the ring incorporates arepeater. When a device receives a signal intended for another device, its repeaterregenerates the bits and passes them along.

Advantage:A ring is relatively easy to install and reconfigure.Each device is linked to only its immediate neighbors.To add or delete a device requires changing only two connections.4. In addition, fault isolation is simplified

In a simple ring, a break in the ring (such as a disabled station) can disable the entirenetwork. This weakness can be solved by using a dual ring or a switch capable of closing offthe break

5. Hybrid Topology:

A network can be hybrid. For example, we can have a main star topology with eachbranch connecting several stations in a bus topology as shown in coming Figure.

6. Tree Topology:

A tree topology combines characteristics oflinear bus and star topologies. It consists ofgroups of star-configured workstationsconnected to a linear bus backbone cable. Treetopologies allow for the expansion of an existingnetwork, and enable schools to configure anetwork to meet their needs.

11

physical / network topology:

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