SUBMITTED BY: Zarghaam Khan. ROLL NO: 0135-BH-BOT-2018. SECTION: G1. TIME: 11:00-12:00. DAY: Wednesday.

NAME:  ZARGHAAM KHAN

ROLL NO:  0135-BH BOT-2018

SECTION:  G1

CLASS DAY:  WEDNESDAY

CLASS TIME:  11:00-12:00

TYPES OF NETWORK TOPOLOGIES AND WHY SHOULD WE USE THEM

Network Topology refers to the physical or logical layout of a network. It defines the way different nodes are placed and interconnected with each other. Alternately, network topology may describe how the data is transferred between these nodes. It is the schematic description of a network arrangement, connecting various nodes (sender and receiver) The way in which the elements of a network are mapped or arranged is known as a network topology. It describes the physical and logical interconnection between the different nodes of a network and defines the way in which they communicate with each other. Network topologies are classified as physical, logical, and signal.

physical topology describes the placement of network nodes and the physical connections between them. This includes the arrangement and location of network nodes and the way in which they are connected.

A logical topology describes the paths taken by data packets as they travel over the network. The logical topology of a network is governed by the protocols used by the data moving over it.

signal topology describes the paths that signals take while they traverse the network. It pertains to the actual connections established by the signals that travel over the network. The terms signal topology and logical topology are closely related and used interchangeably.

point-to-point topology is the most basic way of connecting two terminals. As the name suggests, it is a dedicated permanent link between two network nodes.

In daisy-chaining, multiple nodes are connected with the help of point-to-point connections between consecutive nodes, thus forming a chain. It refers to the linking of a series of devices, which is done linearly or in the form of a ring.

Based on the arrangement of nodes in a network, topologies can be classified as bus, ring, mesh, star, and tree. In these topologies, the network terminals are arranged in a manner suggested by their names. Another type of network topology is hybrid, which uses a combination of two or more topologies.

BUS Topology

Bus topology is a network type in which every computer and network device is connected to single cable. When it has exactly two endpoints, then it is called Linear Bus topology.

Features of Bus Topology

1. It transmits data only in one direction.
2. Every device is connected to a single cable

1. It is cost effective.
2. Cable required is least as compared to other network topology.
3. Used in small networks.
4. It is easy to understand.
5. Easy to expand joining two cables together.

1. Cables fails then whole network fails.
2. If network traffic is heavy or nodes are more the performance of the network decreases.
3. Cable has a limited length.
4. It is slower than the ring topology.

RING Topology

It is called ring topology because it forms a ring as each computer is connected to another computer, with the last one connected to the first. Exactly two neighbours for each device.

Features of Ring Topology

1. A number of repeaters are used for Ring topology with large number of nodes, because if someone wants to send some data to the last node in the ring topology with 100 nodes, then the data will have to pass through 99 nodes to reach the 100th node. Hence to prevent data loss repeaters are used in the network.
2. The transmission is unidirectional, but it can be made bidirectional by having 2 connections between each Network Node, it is called Dual Ring Topology.
3. In Dual Ring Topology, two ring networks are formed, and data flow is in opposite direction in them. Also, if one ring fails, the second ring can act as a backup, to keep the network up.
4. Data is transferred in a sequential manner that is bit by bit. Data transmitted, has to pass through each node of the network, till the destination node.

1. Transmitting network is not affected by high traffic or by adding more nodes, as only the nodes having tokens can transmit data.
2. Cheap to install and expand

1. Troubleshooting is difficult in ring topology.
2. Adding or deleting the computers disturbs the network activity.
3. Failure of one computer disturbs the whole network.

STAR Topology

In this type of topology all the computers are connected to a single hub through a cable. This hub is the central node and all others nodes are connected to the central node.

Features of Star Topology

1. Every node has its own dedicated connection to the hub.
2. Hub acts as a repeater for data flow.
3. Can be used with twisted pair, Optical Fibre or coaxial cable.

1. Fast performance with few nodes and low network traffic.
2. Hub can be upgraded easily.
3. Easy to troubleshoot.
4. Easy to setup and modify.
5. Only that node is affected which has failed, rest of the nodes can work smoothly.

1. Cost of installation is high.
2. Expensive to use.
3. If the hub fails then the whole network is stopped because all the nodes depend on the hub.
4. Performance is based on the hub that is it depends on its capacity

MESH Topology

It is a point-to-point connection to other nodes or devices. All the network nodes are connected to each other. Mesh has n(n-1)/2 physical channels to link n devices.

There are two techniques to transmit data over the Mesh topology, they are :

1. Routing
2. Flooding

MESH Topology: Routing

In routing, the nodes have a routing logic, as per the network requirements. Like routing logic to direct the data to reach the destination using the shortest distance. Or, routing logic which has information about the broken links, and it avoids those node etc. We can even have routing logic, to re-configure the failed nodes.

MESH Topology: Flooding

In flooding, the same data is transmitted to all the network nodes, hence no routing logic is required. The network is robust, and the its very unlikely to lose the data. But it leads to unwanted load over the network.

Types of Mesh Topology

1. Partial Mesh Topology : In this topology some of the systems are connected in the same fashion as mesh topology but some devices are only connected to two or three devices.
2. Full Mesh Topology : Each and every nodes or devices are connected to each other.

Features of Mesh Topology

1. Fully connected.
2. Robust.
3. Not flexible.

1. Each connection can carry its own data load.
2. It is robust.
3. Fault is diagnosed easily.
4. Provides security and privacy.

1. Installation and configuration is difficult.
2. Cabling cost is more.
3. Bulk wiring is required.

TREE Topology

It has a root node and all other nodes are connected to it forming a hierarchy. It is also called hierarchical topology. It should at least have three levels to the hierarchy.

Features of Tree Topology

1. Ideal if workstations are located in groups.
2. Used in Wide Area Network.

1. Extension of bus and star topologies.
2. Expansion of nodes is possible and easy.
3. Easily managed and maintained.
4. Error detection is easily done.

1. Heavily cabled.
2. Costly.
3. If more nodes are added maintenance is difficult.
4. Central hub fails, network fails.

HYBRID Topology

It is two different types of topologies which is a mixture of two or more topologies. For example if in an office in one department ring topology is used and in another star topology is used, connecting these topologies will result in Hybrid Topology (ring topology and star topology).

Features of Hybrid Topology

1. It is a combination of two or topologies

1. Reliable as Error detecting and trouble shooting is easy.
2. Effective.
3. Scalable as size can be increased easily.
4. Flexible.

1. Complex in design.
2. Costly.

One of the main reasons is that they are ideal for small networks because they keep the layout simple. You don’t need lots of cables to link devices together and you don’t need to manage a complex topological setup. This doubles up by making bus topologies cost effective because they can be run with a single cable.

We should use Network Topology because it;

• Plays a significant role in the functioning of networks.
• Helps us better understand the networking concepts.
• Plays a crucial role in performance.
• Helps reduce the operational and maintenance costs such as cabling costs.
• A network topology is a factor in determining the media type to be used to cable a network.
• Error or fault detection is made easy using network topologies.
• Effective utilization of resources and networking components.
•  Networking of computers helps the network users to share data files.
• Users can share devices such as printers, scanners, CD-ROM drives, hard drives etc. Without computer networks, device sharing is not possible.
• Applications can be shared over the network, and this allows to implement client/server applications.

DEFINITION:

Network topology is the interconnected pattern of network elements.A network topology may be physical, mapping hardware configuration, or logical, mapping the path that the data must take in order to travel around the network.

USE:

Network topology can be used to define or describe the arrangement of various types of telecommunication networks, including command and control radio networks, industrial field-buses, and computer networks.

IMPORTANCE:

• The network topology impacts performance.
• The network topology is a factor in determining the media type used to cable the network.
• The network topology impacts the cost of cabling the network.
• Some access methods can work only with specific topologies.
• Helps better understand the important networking concept.
• Creates small-world property.

TYPES OF NETWORK TOPOLOGIES:

1. Bus topology
2. Ring topology
3. Star topology
4. Mesh topology
5. Tree topology
6. Hybrid topology

1. Bus Topology:

• A bus topology is a network topology in which nodes are directly connected to a common linear (branched) or half-duplex link called a bus.
• When a node wants to communicate with other nodes in the network, it simply sends a message to the common bus. All the nodes in the network then receive the message but the node for which it was actually sent only processes it. The other nodes discard the message.

• The bus topology usually requires less cabling.
• The bus topology is relatively simple to configure and install.
• In the bus topology, the failure of one computer does not affect other computers in the network.

• In linear bus topology, failure of the backbone can result in the breakdown of entire network.
• Addition of computers in linear bus topology results in the performance degradation of the network.
• The bus topology is difficult to reconstruct in case of faults.

2. Ring Topology:

• In the ring topology, the nodes are connected in the form of a ring with the help of twisted pair cables.
• Each node is directly connected to the other two nodes in the network. The node, which wants to send a message first passes it to its consecutive node in the network. Data is transmitted in the clockwise direction from one node to another. Each node incorporates a repeater, which passes the message to the next node when the message is intended for another node.

• Each node has an equal access to other nodes in the network.
• Addition of new nodes does not degrade the performance of the network.
• Ring topology is easy to configure and install.

• It is relatively expensive to construct the ring topology.
• The failure of one node in the ring topology affects the other nodes in the ring.

3. Star Topology:

• In the star topology, all nodes are connected to a common device known as Nodes are connected with the help of twisted pair, coaxial cable or optical fiber.
• When a node wants to send a message to the other nodes, it first sends message to the hub, which in turn forwards the message to the intended node. Each node in the network is connected with a point-to-point link to the central hub. The task of the hub is to detect the faulty node present in the network. On the other hand, it also manages the overall data transmission in the network.

• Star topology allows easy error detection and correction.
• In the star topology, the failure of one computer does not affect the other computers in the network.
• Star topology is easy to install.
• Fast performance with few nodes and low network traffic.
• Hub can be upgraded easily.

• In the star topology, the hub failure leads to the overall network crash.
• The star topology requires more cables for connecting the nodes.
• It is expensive due to the cost of the hub.

4. Mesh Topology:

• In mesh topology, each computer is connected to every other computer in point-to-point. For Example; if we have four computers we must have six links. If we have n computers we must have n(n-1)/2 links.
• A message can take several possible paths to reach a destination.

Types of Mesh Topology:

1. Partial Mesh Topology : In this topology some of the systems are connected in the same fashion as mesh topology but some devices are only connected to two or three devices.
2. Full Mesh Topology : Each and every nodes or devices are connected to each other.

• Message delivery is more reliable.
• Network congestion is minimum due to large number of links.
• Each connection can carry its own data load.
• Fault is diagnosed easily.
• It is more safe to use because it provides security and privacy.

• It is very expensive to implement.
• It is very easy to configure and install.
• Bulk wiring is required.

5. Tree Topology:

• It has a root node and all other nodes are connected to it forming a hierarchy. So it is also known as hierarchical topology.
• It is combination of star and bus topologies.

• Point-to-point wiring for individual segments.
• Supported by several hardware and software vendors.
• Expansion of nodes is possible and easy.
• Easy to manage and maintain.
• Errors can be easily detected.

• Overall length of each segment is limited by the type of cabling used.
• If the backbone line breaks the entire segment goes down.
• It is very expensive to implement.

6. Hybrid Topology:

• A hybrid topology is a type of network topology that uses two or more differing network topologies. These topologies include a mix of bus topology, mesh topology, ring topology, star topology, and tree topology.

•  Reliable as Error detecting and trouble shooting is easy.
• Scalable as size can be increased easily.
• Effective.

• Complexity of design.
• Costly Hub.

REFERENCES:

2. https://en.wikipedia.org/wiki/Network_topology
3. https://www.studytonight.com/computer-networks/network-topology-types
4. https://www.computerhope.com/jargon/h/hybrtopo.htm
5. https://www.csestack.org/importance-of-network-topology/

Network Topology

Topic: What are different network of topologies and why we should use them?

Subject: Computer Applications (1201)

Submitted To: Mr.Imran Rafique

Roll Number: 503-BH-MATH-2018

Class: BSC (Hons.)

Section: G1

Date: 05/07/2019

Introduction:
In this tech-driven world, networking plays a crucial role in every individual’s and every organization’s day-to-day activities. But there has to be some specific models or guidelines that must be followed to connect one device to another. This logical or physical layout or configuration of a network is known as a network topology, and if you are an IT pro, here’s what you need to know.

A network topology is a substantial arrangement of a network in which all the nodes are connected with each other using network links or connecting lines. Apart from just describing how the nodes are interconnected, network topology also explains how the data is transferred in a network.

A logical network topology is a high-level representation of how two or more nodes are connected. A logical network topology describes or explains how signals act on a network and how the data is transmitted from one node to another at a very high level. On the other hand, a physical topology describes how nodes are physically connected to each other. The physical connection can be made using wires, wireless connectivity, networking components, and more.

Importance of network topology

• Plays a significant role in the functioning of networks.
• Helps us better understand the networking concepts.
• Plays a crucial role in performance.
• Helps reduce the operational and maintenance costs such as cabling costs.
• A network topology is a factor in determining the media type to be used to cable a network.
• Error or fault detection is made easy using network topologies.
• Effective utilization of resources and networking components.

Network topology classification

Both physical and logical network topologies can be broadly classified into five basic models.

1. Bus topology

Bus topology refers to a network setup where nodes or devices are interconnected using a single cable. It is because of this setup why bus topology is often referred to as line topology or backbone. Depending on the nodes or devices that need to be connected, a coaxial cable or an RJ45 cable is typically used to connect the devices.

Shutterstock

Bus topology usually consists of two ends and signals travel from one end to another. Bus topology is unidirectional and data is transferred from one end to another in a single direction.

• Cost-effective.
• Less cable required to connect the nodes.
• Very easy to understand.
• Provides an easy feasibility to extend or to reduce a network.
• Ideal for small network setups.

• Ideal only for small network setups.
• If the backbone (primary) cable fails, the entire network fails.
• Transmission speeds are drastically reduced with the increased number of nodes.

2. Ring topology

As the name suggests, a ring network topology forms a ring as each node or computer in a network are connected to each other in a circular manner. Every node or device in a ring topology will have exactly two neighbors and accordingly, the last node in the network will be connected to the first node.

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In a ring topology, all devices are connected in a closed loop configuration and one node in the network acts as a monitor, which essentially takes care of the configuration. In a ring topology, all the data packets are transmitted from one node to another in a circular manner and, therefore, for a data packet to reach one point to another it has to traverse through all the intermediate nodes. For large networks with more nodes connected in a ring, repeaters can be used to prevent data loss in these data transmissions.

3.Dual ring topology

The data transmission is usually unidirectional in a ring network topology but it can be configured to support bidirectional transmissions as well. This is known as dual ring topology and can be configured by having two connections between each network node.

In a dual ring topology, two rings are formed between the nodes. One ring supports data flow in one direction, while the other ring supports the data flow in another direction, making it unidirectional. Another important advantage of a dual ring topology is that one ring out of the two can act as a backup for another in case of any failures, ensuring the network continuity.

• Performs better than bus topology under heavy network loads.
• Point-to-point connectivity of the nodes makes it easy to identify and detect misconfigurations or faults.
• Orderly network flow.
• Cost effective to implement.

• One malfunctioning node can collapse the whole network.
• Transmission line failure can take down the whole network.
• Communication delay is proportional to the number of nodes in a ring.
• Bandwidth is shared among all the devices in a network.
• Reconfiguring, adding, or removing nodes requires the network to shut down.

4.  Star topology

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In a star topology, every node in the network is connected to a central computer or a node, which takes care of the network. Every device in the network has a direct connection to the central node and every node is indirectly connected to other nodes using the central node.

All the data in a star topology flow through the central hub before it reaches its destination. The central hub manages and controls all data transfers and connectivity in a star topology. The central hub also acts as a repeater to make sure there is zero or minimal data loss during the transmissions. A star topology can be configured using a twisted pair, coaxial cable, or an optical fiber.

• Failure of one node will not affect the entire network.
• Devices can be added, removed, reconfigured, or modified without disturbing the network.
• Less cabling is needed to configure star topology.
• Easy to set up and modify.
• Easy to troubleshoot.

• The entire network is dependent on the central hub: If the hub fails, then the whole network will be down.
• Expensive to install and use.
• Performance is solely based on the central hub’s configuration, power, and efficiency.

5. Mesh topology

Mesh topology is a widely used network model that has a point-to-point connection between each node in the network. Every node or a device in a mesh network connects to other nodes directly and in a non-hierarchical manner. In a mesh network, the network isn’t dependent on a single machine like the star topology and every node plays an active role in the relay of information.

Data transmission in a mesh topology is based on two important techniques.

1) Routing

2) Flooding

5.1 Routing

Every node in a mesh network can have a routing logic and transmission of data or information happens through that routing logic. This routing logic can be used to find the shortest distance to send some information from sender to receiver or the logic can be used to avoid using broken lines for data transmission.

5.2 Flooding

In the case of flooding, the same data is transmitted to each node in the network. Therefore, no routing logic is required in case of flooding mesh networks. Loss of data is highly unlikely as every node will have the same data with them. This makes it robust and fault-tolerant. However, this also increases the load on the network.

• Fully connected.
• Provides security and privacy.
• Any node failure won’t affect the network.
• Less load and collisions to dedicated lines.
• Isolation and fault-detection are easy.

• Cost of implementing and cost of cabling is high.
• Installation and reconfiguring is a typical task.
• Complex to understand.

6. Hybrid topology

When a network topology is formed by integrating two or more topologies together, this results in a hybrid topology. Hybrid topologies can be configured as per the company’s requirement. When configured properly, hybrid topologies can provide the best of all the network topologies. Hybrid topologies are easy to scale and expand. However, they might need higher costs and more operational efforts to configure and maintain.

7. Tree topology

A tree network topology is one of the most common examples of a hybrid topology. It is also referred as a star-bus network topology in which star networks are interconnected with one another using a bus network. In a tree topology, nodes are connected with one another in a hierarchical manner and are therefore also known as hierarchal topology.

• Scalable; Easy to add or remove nodes.
• Suitable for large networks.
• Easy to manage.

• Complex to design and maintain.

Choosing the right network topology depends on multiple factors such as the number of nodes to be involved in the network, geographical distance between the nodes, finances, maintenance, operational flexibility, and more.

Every topology we discussed above has its own advantages and disadvantages. Therefore, the key to build and configure the right networking model is subjective. For any company, it is very important to first gather all the requirements and needs before adopting any particular network topology

INDEX

Introduction

Importance of network topology

Network topology classification

5.1 Routing

5.2 Flooding

Abstract:

Network design involves the art and science of meeting requirements while dealing with economic, technological, physical, and political constraints. Scalability and extensible are the hallmarks of a successful large-scale network design, and are encouraged through layering, modulation, and hierarchy. Randomisation, soft state, dampening, separation of the control plane, marginalization’s, and optimising the common case are also important considerations for routing protocols and the overall routing topology.

Although requirement analysis is an important aspect of design, it should be viewed as an ongoing task and should be ratified by the collection of traffic statistics that describe actual network usage.

By categorising routers into the roles of backbone, distribution, and access, you will simplify the hardware/software combinations and configuration complexity required for any particular router. This consequently simplifies the operational support of the network.

Within the various tiers of the hierarchy, the typologies of ring, star, bus, and mesh may be employed. The choice depends on reliability, traffic, and delay requirements. In the case of WAN typologies, carrier service pricing also could be a determining factor.

Definition:

Network topology is the arrangement of the elements (links, nodes, etc.) of a communication network. Network topology can be used to define or describe the arrangement of various types of telecommunication networks, including command and control radio networks, industrial field-buses, and computer networks.

LANs and WANs  Geographical coverage

• LANs: A single geographical location, such as office building, school, etc. – Typically, High speed and cheaper.
• WANs: Spans more than one geographical location often connecting separated LANs Slower Costly hardware, routers, dedicated leased lines and complicated implementation procedures.

Network topologies describe the ways in which the elements of a network are mapped. There are two ways of defining network geometry:

• Physical topology
• Logical (or signal) topology.

Physical topology emphasises the physical layout of the connected devices and nodes, while the logical topology focuses on the pattern of data transfer between network nodes.

Types of Network Topology:

The physical and logical network topologies of a network do not necessarily have to be identical. However, both physical and network topologies can be categorised into five basic models:

• Bus Topology
• Star Topology
• Ring Topology
• Mesh Topology
• Tree Topology
• Hybrid Topology

Bus Topology:

Bus topology is a network type in which every computer and network device is connected to single cable. It transmits the data from one end to another in single direction. No bi-directional feature is in bus topology.

Popular on LANs because they are inexpensive and easy to install.

• If N devices are connected to each other in bus topology, then the number of cables required to connect them is 1 ​which is known as backbone cable and N drop lines are required.
• Cost of the cable is less as compared to other topology, but it is used to build small networks.

Problems with this topology:

• If the common cable fails, then the whole system will crash down.
• If the network traffic is heavy, it increases collisions in the network. To avoid this, various protocols are used in MAC layer known as Pure Aloha, Slotted Aloha, CSMA/CD etc.

Mesh Topology:

In mesh topology, every device is connected to another device via channel.

• If suppose, N number of devices relate to each other in mesh topology, then total number of ports that is required by each device is ​ N-1. In the Figure 1, there are 5 devices connected to each other, hence total number of ports required is 4.
• If suppose, N number of devices relate to each other in mesh topology, then total number of dedicated links required to connect them is NC2e. N(N-1)/2. In the Figure 1, there are 5 devices connected to each other, hence total number of links required is 5*4/2 = 10.

• It is robust.
• Fault is diagnosed easily. Data is reliable because data is transferred among the devices through dedicated channels or links.
• Provides security and privacy.

Problems with this topology:

• Installation and configuration are difficult.
• Cost of cables are high as bulk wiring is required, hence suitable for a smaller number of devices.
• Cost of maintenance is high.

Star Topology:

In star topology, all the devices are connected to a single hub through a cable. This hub is the central node and all other nodes are connected to the central node. The hub can be passive ​in nature i.e. not intelligent hub such as broadcasting devices, at the same time the hub can be intelligent known as active ​hubs. Active hubs have repeaters in them.

• If N devices are connected to each other in star topology, then the number of cables required to connect them is N. So, it is easy to set up.
• Each device requires only 1 port i.e. to connect to the hub.

Problems with this topology:

• If the concentrator (hub) on which the whole topology relies fails, the whole system will crash down.
• Cost of installation is high.
• Performance is based on the single concentrator i.e. hub.

Tree Topology:

It has a root node and all other nodes are connected to it forming a hierarchy. It is also called hierarchical topology. It should at least have three levels to the hierarchy.

1. Extension of bus and star topologies.
2. Expansion of nodes is possible and easy.
3. Easily managed and maintained.
4. Error detection is easily done.

1. Heavily cabled.
2. Costly
3. If more nodes are added maintenance is difficult.
4. Central hub fails, network fails.

Ring Topology:

In this topology, it forms a ring connecting a devices with its exactly two neighbouring devices.

The following operations takes place in ring topology are:

1. One station is known as monitor station which takes all the responsibility to perform the operations.
2. To transmit the data, station must hold the token. After the transmission is done, the token is to be released for other stations to use.
3. When no station is transmitting the data, then the token will circulate in the ring.
4. There are two types of token release techniques: Early token releases the token just after the transmitting the data and Delay token release releases the token after the acknowledgement is received from the receiver.

• The possibility of collision is minimum in this type of topology.
• Cheap to install and expand.

Problems with this topology:

• Troubleshooting is difficult in this topology.
• Addition of stations in between or removal of stations can disturb the whole topology.

Hybrid Topology:

This topology is a collection of two or more topologies which are described above. This is a scalable topology which can be expanded easily. It is reliable one but at the same it is a costly topology.

1. Reliable as Error detecting and troubleshooting is easy.
2. Effective
3. Scalable as size can be increased easily.
4. Flexible

1. Complex in design.
2. Costly

Cover Letter and CV

IQRAR-UL-HASSAN

Iqrar-Ul-Hassan

0946-BH-BAF2018

0303-4841287
iuh1681@gmail.com

May 5, 2019

Science Block GC University Kehchery Road Lahore.

Dear Mr. Imran,

I am writing to apply for the programmer position advertised in the Times Union. As requested, I enclose a completed job application, my certification, my resume and three references.

The role is very appealing to me, and I believe that my strong technical experience and education make me a highly competitive candidate for this position. My key strengths that would support my success in this position include:

• I have successfully designed, developed and supported live-use applications.
• I strive continually for excellence.
• I provide exceptional contributions to customer service for all customers.

With a BS degree in Computer Programming, I have a comprehensive understanding of the full lifecycle for software development projects. I also have experience in learning and applying new technologies as appropriate. Please see my resume for additional information on my experience.

I can be reached anytime via email at iuh1681@gmail.com or by cell phone, 0303-4841287.

Sincerely,

Signature (hard copy letter)

Iqrar-Ul-Hassan

Network Topology:

A network can be configured or arranged in different ways. Computer in a network have been connected in some logical manner. The layout of different pattern interconnection between in a network is called network topology. It is a shape of network.

How Network Topology Is Determined:

A network topology defines the way that how they are arranged, including all of its nodes or intersecting points lines connecting to the various network elements. Typologies are generally illustrated in schematic or diagrammatic form with symbols, icons representing the nodes and lines depicting the connections or runs of cable.

The communications type and the protocols used in making connections may be defines by a signal or logical networks topology. The geometric configuration of workstations and cables is described by a physical network topology. Physical network topologies come in a variety of forms.

TYEPS OF NETWORK TOPOLOGIES:

• POINT TO POINT
• BUS TOPOLOGY
• STAR TOPOLOGY
• RING TOPOLOGY
• MESH TOPOLOGY
• TREE TOPOLOGY
• HYBRID TOPOLOGY

POINT TO POINT:

Point-to-point topology is the network type which connects two nodes directly together.

EXAMPLES:

• A workstation communicating along a parallel cable with a printer.
• A mainframe terminal communicating with a front end processor.
• Two computers communicating through modems devices.

BUS TOPOLOGY:

Bus topology is the simplest topology. In this topology all computers or networks nodes are connected to common communication medium. This medium is often known as bus. The terminator is used at the end of bus to absorb signal when it has exactly two end points, then it is called as a “Linear Bus topology.”

Working of Bus Topology:

The sending computer send the data and destination address to the bus the data and address move room one computer to another in the network. Each computer checks the address. If it match with the address of computer, the computer keeps the data otherwise data moves to next computer.

USES:

All the devices available on the network are effectively connected with each other so any communication sent into the bus by using a device is visible to all the other devices –but only the specific device for which the message is intended should access and process it. Data is usually transmitted in only one direction.

• It works well when you have small network.
•  If one node fail it does not affect the rest of network
• It requires less cable length as compared to other topologies.
• It is easy to understand.
• It is cost less.

• It is difficult to troubleshoot.
• When Cables fails then whole network fails.
• If network traffic is heavy the performance of the network decreases.
• Cable is of limited length.
• It only supports small number of computers.
• It is slower than other topologies.

STAR TOPOLOGY:

This type of topology in all the computers is connected with a single hub through cable. This hub is a central node and all the others nodes are connected with central node.

Working of star Topology:

The sending computer sends data to hubs the send data to receiving computers. Each computer in star network communicates the center hub.

• It is to maintain and modify the network.
• Fast performance with low network traffic.
• Hubs can be upgraded easily.
• Easy to troubleshot.

USES:

Star topology usually used in client server networks. The star network topologies are common in the home networks, where central connection points are a router, switch, or network hub. Unshielded Twisted Pair Ethernet cabling is used in order to connect the devices to hub, using coaxial cable or optical fibers can also be employed. As compared to bus topology, star network usually requires more cabling.

• It require a large length of cable to connect with computer.
• Very expensive to use.
• Performance of this network is based on hub that is depends on its own capacity.

RING TOPOLOGY:

In ring network usually every device has exactly two neighbors for communication purposes. All messages travel through a ring in the same direction (either “clockwise” or “counterclockwise”)

Working of Ring Topology:

Every computer is connected to Next computer in a ring each computer receives the message from previous computer and transmits it to the next computer .this message follows the uni direction. The message is passed around the ring until it reached the correct destination computer.

USES:

Ring network typologies are usually found on different school campuses; using some commercial organizations we can also use them. FDIC, SONNET, or Token Ring technology is mostly used. Data is transported usually a bit by bit from each node until it reaches it’s a destination point. With a large numbers of nodes, repeaters must be used to keep data signals “fresh” as they travel across the network.

• It is less expensive than star topology
• All data usually flows in one direction only reducing the chance of packets collisions.
• A network server is not needed to control network connectivity between each workstation.

• It is difficult to troubleshoots
• Data is transferred over the network that has to pass through each workstation on the network which can make it slower than a star topology.
• The major disadvantages of a ring topology are that if any individual connection in the ring is broken down, the entire network is also affected.

MESH TOPOLOGY:

In mesh topology every device the network is physically connected to every other device in the network.

In flooding, the same data is transmitted to all network nodes hence no routing logic is required. The network is robust, and is very unlikely to lose the data. But it lead unwanted load over the network.

Techniques of Mesh Topology:

1-Routing                                                            2-Flooding

• Routing:

In routing the nodes have a routing logic, as per the network requirements. Like routing logic to direct the data to reach the destination using the shortest distance. Or, routing logic which has information about the broken links, and it avoids that node etc. We can even have routing logic to re-configure the failed nodes.

• Flooding:

In flooding, the same data is transmitted to all the network nodes; hence no routing logic is required. The network is robust, and the it’s very unlikely to lose the data. But it leads to unwanted load over the network.

TYPES:

• Partial Mesh Topology: In this topology some of the systems are connected in the same fashion as mesh topology but some devices are only connected to two or three devices.
• Full Mesh Topology: Each and every nodes or devices are connected to each others.

USES:

Communications made on a mesh network topology may take any of several possible paths from their source to their destination. Mesh network topologies are typical of the internet, and certain wide area networks (WANs). Data may be transmitted via a routing logic, which is determined by set criteria such as “path of shortest distance” or “avoid broken links.

TREE  TOPOLOGY:

A tree topology combines the characteristics of star and bus .A tree topology is a special type of structure in which many connected elements are arranged like the branches of a tree.

FOR EXAMPLE:

Tree typologies are frequently used to organize the computers in a corporate    network, or the information in a database.

• Extension of bus and star topologies.
• Expansion of nodes is possible and easy.

• Heavily cabled.
• Costly.
• When central hub fails, network fails.

HYBRID TOPOLOGY:

It is two different types of topologies which is a mixture of two or more topologies In fact it’s typical of an approach that combines two or more network topologies in order to maximal Advantages:

• Reliable as Error detecting and trouble shooting is easy.
• Effective.
• Flexible.

• Complex in design.
• Costly.

Physical vs. Signal Topology:

Finally, a distinction should be made between physical topologies and signal topology governing the transfer of data.

In many cases, both physical and signal topologies are the same – but this isn’t always true. So for example, some networks may have a star network topology as they’re physically laid out, but data may be routed through them on a bus or ring network topology basis.

Summary

Topology remains an important part of network design theory. You can probably build a home or small business computer network without understanding the difference between a bus design and a star design, but becoming familiar with the standard topologies gives you a better understanding of important networking concepts like hubs, broadcasts, and routes.

INDEX

1.   Topology

• Physical topology
• Logical topology

2.   Bus topology

• Distributed bus topology
• Linear bus topology

3.   Mesh topology

• Fully mesh
• Partially mesh

5.   Ring topology

• Unidirectional ring topology
• Bidirectional ring topology

6.   Star topology

• Extended star
• Distributed star

8.   Point-to-point topology

• Permanent point-to-point
• Switched point-to-point

9.   Uses of network topologies

TOPOLOGY

Two different definitions of topology are as follows:  physical and logical.

The physical topology of a network is the layout or actual appearance of the cabling scheme used on a network.

The logical topology of a network describes how the data flows through the physical topology.

Physical Topologies

All physical topologies are variations of two fundamental methods of connecting devices:  point-to-point and multipoint.

The following four types of physical topologies are frequently used in computer networking:

1. Star
2. Bus
3. Ring
4. Hybrid

And also these topologies are divided into sub topologies, there are some other topologies also which are included in Logical topologies.

BUS TOPOLOGY

Definition:

Bus topology is a specific kind of network topology in which all of the various devices in the network are connected to a single cable or line. In general, the term refers to how various devices are set up in a network.

A signal from the source is broadcasted and it travels to all workstations connected to bus cable. A terminator is added at ends of the central cable, to prevent bouncing of signals. A barrel connector can be used to extend it.

Figure:

Figure 1 BUS TOPOLOGY

Types of bus topology:

There are two main types of bus topology:

1. Distributed bus topology
2. Linear bus topology
• Distributed bus:

In a distributed bus topology, there may be more than one linear pattern connected to the network.

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 that are created by adding branches to the main section of the transmission medium is known as distributed bus topology.

• Linear bus topology:

Linear bus topology is a type of network topology in which each devices connected one after the other in a sequential chain. A linear bus topology implies that there is just one line associated with two distinct endpoints.

• Bus topologies are often valued for their simplicity and lower cost of
• For a small network, bus topology works well.
• Installation of Bus topology is very easy as compared to other topologies.
• Cable length required for this topology is the least compared to other networks.

• If the central line is compromised, the entire network will go down.
• It can be difficult to troubleshoot these kinds of systems, and problems like data signal loss can occur with a longer linear cable.
• Its security is very low because all the computers receive the sent signal from the source.
• Bus topology is not well workable for larger networks, Terminators are required for both ends of the main cable.

MESH TOPOLOGY

DEFINITION:

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 is called mesh topology. Routers are used to provide the best and most efficient data path for effective communication. In the event of a hardware failure, many routes are available to continue the network communication process.

Figure:

Figure 3 MESH TOPOLOGY

Types of Mesh topology:

There are two main types of mesh topologies:

1. Fully connected network
2. Partially connected network
• Fully mesh topology:

In a full mesh topology, every computer in the network has a connection to each of the other computers in that network.  This provides greater redundancy, because if any node fails, the network traffic can be directed using other nodes.

• Partial mesh topology:

In a partially connected mesh topology, at least two of the computers in the network have connections to multiple other computers in that network. It is an inexpensive way to implement redundancy in a network.

• If a break occurs in a segment of cable, traffic can still be rerouted using the other cables.
• This topology is rarely used because of the significant cost and work involved in having network components directly connected to every other component.
• A mesh topology provides redundant links across the network.

• The chance of redundant connection is high, which adds to the high cost and potential to reduced efficiency.
• The installation and maintenance of mesh topology is difficult.
• It is quite expensive as compared to other topologies.

TREE TOPOLOGY

Definition:

A tree topology is a special type of structure in which many connected elements are arranged like the branches of a tree. Tree topologies are frequently used to organize the computers in a corporate network, or the information in a database.

Experts may define a tree topology as a combination of star and bus                  topologies, where multiple elements are connected through a single lateral connection.

Figure:

Figure 5 TREE TOPOLOGY

https://fcit.usf.edu/network/chap5/chap5.htm

• A Tree topology is a good choice for large computer networks as the tree topology “divides” the whole network into parts that are more easily manageable.
• Detection and correction of faults is easy because each device is connected to a central device through a dedicated link.
• Easy to expend and implementation the network. If one device is damaged then the other devices are not affected.

• If there is a problem with the main cable, the entire network goes down.
• This network is not secure, anyone can see transmitted data.
• The maintenance becomes difficult as more and more nodes and segments are added

RING TOPOLOGY

Definition:

The topology in which all of the nodes are connected in a closed loop and messages travel around the ring, with each node reading those messages addressed to it. This type of topology is called ring topology.

Ring topology refers to a specific kind of network setup in which devices are connected in a ring and pass information to or from each other according to their adjacent proximity in the ring structure.

Figure:

Figure 6 RING TOPOLOGY

http://slogcsc104.blogspot.com/2012/11/networks.html

Types of ring topology:

There are two types of the Ring Topology based on the data flow:

1. Unidirectional ring topology
2. Bidirectional ring topology
• Unidirectional ring:

Most ring topologies allow packets to travel only in one direction, called a unidirectional ring network.

• Bidirectional ring:

Most ring topologies permit data to move in either direction, called bidirectional.

• it can span larger distances than other types of networks because each node regenerates messages as they pass through it.
• It has ability to handle heavy network communications better than some other setups.
• Installation and troubleshooting are also relatively easy with this kind of network.
• Installation and troubleshooting are also relatively easy with this kind of network.
• Reduced chances of data collision as each node release a data packet after receiving the token.

• Just one failure to transmit data can impact the entire network.
• The hardware needed to connect each workstation to the network is more expensive than Ethernet cards and hubs/switches.
• Moving, adding and changing the devices can affect the network.
• In ring topology, the maximum ring length and numbers of nodes are limited.

STAR TOPOLOGY

Definition:

In a star network devices are connected to a central computer, called a hub. Nodes communicate across the network by passing data through the hub.

Figure:

Figure 7 STAR TOPOLOGY

https://fcit.usf.edu/network/chap5/chap5.htm

Types of star topology:

There are two types of star topology:

1. Extended star
2. Distributed star
• Extended star:

The extended star network topology extend a physical star topology by one or more repeaters between the central node and the peripheral (spoke) nodes.

• Distributed star:

A type of network topology that is composed of individual networks that are based upon the physical star topology connected in a linear fashion is known as distributed star topology.

• In a star network, one malfunctioning node doesn’t affect the rest of the network.
• Easy to install and wire.
• No disruptions to the network when connecting or removing devices.
• Easy to detect faults and to remove parts.

• It requires more cable length than a linear topology.
• If the hub, switch, or concentrator fails, nodes attached are disabled.
• It is more expensive than linear bus topologies because of the cost of the hubs, etc.

HYBRID TOPOLOGY

Definition:

Hybrid topology  uses two or more different network topologies. These topologies include a mix of bus topology, mesh topology, ring topology, star topology, and tree topology.

Figure:

Figure 8 HYBRID TOPOLOGY

https://www.slideshare.net/siddiqueibrahim37/network-topologyppt

• It is very reliable and easy to detect the Faulty system.
• Troubleshooting from hybrid topology is easy.
• It includes both wired and wireless network.
• It is an expandable network.

• Its design is difficult to understand.
• The cost of this network design is high, because of the requirement of a lot of cables, cooling systems, etc.
• For hybrid topology, MAU ( Multi-station Access Unit) is required.

POINT-TO-POINT TOPOLOGY

Definition:

Point To point (PTP) topology connects two nodes directly together. n this topology, two same ports of devices are connected directly to each other.

The following EXAMPLES are pure

• Two computers communicating via

modems.

• A mainframe terminal communicating

with a front end processor.

• A workstation communicating along a

parallel cable to a printer.

Figure:

Figure 9 POINT-TO-POINT TOPOLOGY

Types:

There are two types of point-to-point topology:

1. Permanent point-to-point
2. Switched point-to-point

• Highest Bandwidth
• Low Latency
• Very simple connectivity
• Easy to handle
• Replace it in few seconds Genuinely

There are no bad points for this topology except Link fails due to port fails.

DAISY CHAIN TOPOLOGY

Definition:

Daisy chain is the other most adopted topology in traditional industrial automation networks. Cable segments interconnect multiple devices, being the devices part of the network cable.

Figure:

Figure 10 DAISY CHAIN TOPOLOGY https://www.tutorialspoint.com/data_communication_computer_network/computer_network_topologies.htm

Types:

There are two types of daisy chain topology:

1. Ethernet daisy chain
2. Deploying daisy chain

• Dual port Ethernet devices only support 10 Mbit/s and/or 100 Mbit/s operational speeds and must use one or the other.
• The network will operate only as fast as the slowest device that is connected to the network.

USES OF NETWORK TOPOLOGIES

1. Network topologies plays a significant role in the functioning of networks.
2. Network topologies Helps us better understand the networking concepts.
3. Network topologies Plays a crucial role in performance.
4. These topologies Helps reduce the operational and maintenance costs such as cabling costs.
5. A network topology is a factor in determining the media type to be used to cable a network.
6. Error or fault detection is made easy using network topologies.
7. Effective utilization of resources and networking components.

REFERENCES

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NETWORK TOPOLOGIES