A TOTAL GUIDE ABOUT

NETWORK TOPOLOGIES

© H i m a n s h u

What you will learn today?

Introduction To Network Topology

Factor Choosing Network Topology

Types of Network Topology

Bibliography + Useful Sites

NETWORK TOPOLOGIES

• Topology refers to the layout of connected devices on a network.

• Simply it’s a :Layout of a network and how different nodes in anetwork are connected to each other and how they communicate.

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CONCEPT

• Computer network topology is the way various components of anetwork (like nodes, links, peripherals, etc) are arranged. Networktopologies define the layout, virtual shape or structure of network,not only physically but also logically. The way in which differentsystems and nodes are connected and communicate with eachother is determined by topology of the network. Topology can bephysical or logical. Physical Topology is the physical layout of nodes,workstations and cables in the network; while logical topology isthe way information flows between different components.

In general, physical topology relates to a core network whereaslogical topology relates to basic network.

FACTORS WHILE CHOOSING TOPOLOGIES

• Scale of your project (in terms of number of components to beconnected)

• Amount of traffic expected on the network.

• Budget allotted for the network i.e. amount of money you arewilling to invest.

• Required response time.

TOPOLOGY TYPES

• There are two basic categories of network topologies: physical topologies and logical topologies.

PHYSICAL TOPOLOGIES

CONCEPT

• The physical topology of a network is the actual geometric layout of workstations. There are several common physical topologies, as I am describing below and as shown in the figure.

• Simply, I can say Physical topology is the physical layout of nodes on a network

Peps, Now I will take you to the next level. Lets learn about there types

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TYPES OF PHYSICAL TOPOLOGIES1.FULLY CONNECTED

DESCRIPTION

• A fully connected network, complete topology, or full meshtopology is a network topology in which there is a direct linkbetween all pairs of nodes. Networks designed with this topologyare usually very expensive to set up, but provide a high degree ofreliability due to the multiple paths for data that are provided bythe large number of redundant links between nodes. This topologyis mostly seen in military applications.

ADVANTAGES

• A fault in one terminal on the network will not effect the rest

• When network usage is high, data packets can be transmitted viadifferent cables, thereby reducing network clogging - keeping datatransfer rates at an acceptable level..

DISADVANTAGES

• A large amount of cabling is required

2. BUS

CONCEPT

In this topology every workstation is connected to a maincable called the bus. Therefore, in effect, each workstation isdirectly connected to every other workstation in the network.

DESCRIPTION

• Single cable connects all network nodes without intervening connectivity devices

• Devices share responsibility for getting data from one point to another

• Terminators stop signals after reaching end of wire

– Prevent signal bounce

• Inexpensive, not very scalable

• Difficult to troubleshoot, not fault-tolerant

ADVANTAGES

• Works well for small networks

• Relatively inexpensive to implement

• Easy to add to it

DISADVANTAGES

• Management costs can be high

• Potential for congestion with network traffic

3. STAR

CONCEPT

• In this topology, there is a central computer or server to which all theworkstations are directly connected. Every workstation is indirectlyconnected to every other through the central computer.

DESCRIPTION

• Any single cable connects only two devices

– Cabling problems affect two nodes at most

• Requires more cabling than ring or bus networks

– More fault-tolerant

• Easily moved, isolated, or interconnected with other networks

– Scalable

• Supports max of 1024 addressable nodes on logical network

ADVANTAGES

• Good option for modern networks

• Low startup costs

• Easy to manage

• Offers opportunities for expansion

• Most popular topology in use; wide variety of equipment available

DISADVANTAGES

• Hub is a single point of failure

• Requires more cable than the bus

4. RING

CONCEPT

In this topology, the workstations are connected in a closed loopconfiguration. Adjacent pairs of workstations are directlyconnected. Other pairs of workstations are indirectly connected,the data passing through one or more intermediate nodes.

DESCRIPTION

• Each node is connected to the two nearest nodes so the entirenetwork forms a circle

• One method for passing data on ring networks is token passing

• Each workstation transmits data

ADVANTAGES

• Easier to manage easier to locate a defective node or cable problem

• Well-suited for transmitting signals over long distances on a LAN

• Handles high-volume network traffic

• Enables reliable communication

DISADVANTAGES

• Expensive

• Requires more cable and network equipment at the start

• Not used as widely as bus topology

– Fewer equipment options

– Fewer options for expansion to high-speed communication

5. MESH

CONCEPT

• In this topology employs either of two schemes, called full meshand partial mesh. In the full mesh topology, each workstation isconnected directly to each of the others. In the partial meshtopology, some workstations are connected to all the others, andsome are connected only to those other nodes with which theyexchange the most data

DESCRIPTION

• Each of the network node, computer and other devices, areinterconnected with one another. Every node not only sends itsown signals but also relays data from other nodes. In fact a truemesh topology is the one where every node is connected to everyother node in the network. This type of topology is very expensiveas there are many redundant connections, thus it is not mostly usedin computer networks. It is commonly used in wireless networks.Flooding or routing technique is used in mesh topology.

ADVANTAGES

• Data can be transmitted from different devices simultaneously. Thistopology can withstand high traffic.

• Even if one of the components fails there is always an alternativepresent. So data transfer doesn’t get affected.

• Expansion and modification in topology can be done withoutdisrupting other nodes

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DISADVANTAGES

• There are high chances of redundancy in many of the networkconnections.

• Overall cost of this network is way too high as compared to othertopologies.

• Set-up and maintenance of this topology is very difficult. Evenadministration of the network is tough.

6. TREE

CONCEPT

• In this topology uses two or more star networks connectedtogether. The central computers of the star networks are connectedto a main bus. Thus, a tree network is a bus network of starnetworks.

DESCRIPTION

Tree Topology integrates the characteristics of Star and BusTopology. Earlier we saw how in Star network Topology, computers(nodes) are connected by each other through central hub. And wealso saw in Bus Topology, work station devices are connected by thecommon cable called Bus. After understanding these two networkconfigurations, we can understand tree topology better. In TreeTopology, the number of Star networks are connected using Bus.This main cable seems like a main stem of a tree, and other starnetworks as the branches. It is also called Expanded Star Topology.Ethernet protocol is commonly used in this type of topology. Thediagram below will make it clear.

ADVANTAGES

• It is an extension of Star and bus Topologies, so in networks wherethese topologies can't be implemented individually for reasonsrelated to scalability, tree topology is the best alternative.

• Expansion of Network is possible and easy.

• Here, we divide the whole network into segments (star networks),which can be easily managed and maintained.

• Error detection and correction is easy.

• Each segment is provided with dedicated point-to-point wiring tothe central hub.

• If one segment is damaged, other segments are not affected.

DISADVANTAGES

• Because of its basic structure, tree topology, relies heavily on themain bus cable, if it breaks whole network is crippled.

• As more and more nodes and segments are added, themaintenance becomes difficult.

• Scalability of the network depends on the type of cable used.

7.HYBRID

CONCEPT

• Hybrid networks use a combination of any two or more topologies,in such a way that the resulting network does not exhibit one of thestandard topologies (e.g., bus, star, ring, etc.). For example a treenetwork connected to a tree network is still a tree networktopology. A hybrid topology is always produced when two differentbasic network topologies are connected. Two common examples forHybrid network are: star ring network and star bus network

ADVANTAGES

• Reliable: Unlike other networks, fault detection and troubleshootingis easy in this type of topology. The part in which fault is detected canbe isolated from the rest of network and required correctivemeasures can be taken, WITHOUT affecting the functioning of rest ofthe network.

• Scalable: Its easy to increase the size of network by adding newcomponents, without disturbing existing architecture.

• Effective: Hybrid topology is the combination of two or moretopologies, so we can design it in such a way that strengths ofconstituent topologies are maximized while there weaknesses areneutralized.

DISADVANTAGES

• Complexity of Design: One of the biggest drawback of hybridtopology is its design. Its not easy to design this type of architectureand its a tough job for designers. Configuration and installationprocess needs to be very efficient.

• Costly Hub: The hubs used to connect two distinct networks, arevery expensive. These hubs are different from usual hubs as theyneed to be intelligent enough to work with different architecturesand should be function even if a part of network is down.

• Costly Infrastructure: As hybrid architectures are usually larger inscale, they require a lot of cables, cooling systems, sophisticatenetwork devices, etc.

LOGICAL TOPOLOGY

• Logical (or signal) topology refers to the 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. For example, some networks are physically laid out in a star configuration, but they operate logically as bus or ring networks.

DESCRIPTION

• Logical topology: how data is transmitted between nodes

– May not match physical topology

• Bus logical topology: signals travel from one network device to all other devices on network

– Required by bus, star, star-wired physical topologies

• Ring logical topology: signals follow circular path between sender and receiver

– Required by ring, star-wired ring topologies

BIBLIOGRAPHY&

USEFUL SITES TO LEARN TOPOLOGY

• Techtarget.com

• Slideshare.net

• Wikipedia.org

• Google.com/images (Images sources)

• bit.ly/anonnepal (Writer)

• Ianswer4u.com

• Dreamstime.com (Background Images)

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