NETWORK TOPOLOGY

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TOPOLOGY

In computer networking, topology refers to the layout of connected devices.

Network topology is defined as the interconnection of the various elements (links, nodes, etc.) of a computer network. Network Topologies can be physical or logical. Physical Topology means the physical design of a network including the devices, location and cable installation. Logical topology refers to how data is actually transferred in a network as opposed to its physical design.

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Created By : B. Sarangi, Sr. Lecturer.

Topology can be considered as a virtual shape or structure of a network. This shape does not correspond to the actual physical design of the devices on the computer network. The computers on a home network can be arranged in a circle but it does not necessarily mean that it represents a ring topology.

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Any particular network topology is determined only by the graphical mapping of the configuration of physical and/or logical connections between nodes. The study of network topology uses graph theory. Distances between nodes, physical interconnections, transmission rates, and/or signal types may differ in two networks and yet their topologies may be identical.

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Created By : B. Sarangi, Sr. Lecturer.

Types of TOPOLOGY

Based on their shape and structures there are several types of network topologies. Some of them are :

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• BUS
• RING
• STAR
• TREE
• MESH
• HYBRID

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Created By : B. Sarangi, Sr. Lecturer.

BUS TOPLOLGY

• A bus network uses a multi-drop transmission medium, all node on the network share a common bus and thus share communication. This allows only one device to transmit at a time. A distributed access protocol determines which station is to transmit. Data frames contain source and destination addresses, where each station monitors the bus and copies frames addressed to itself.
• A bus topology connects each computer (nodes) to a single segment trunk (a communication line, typically coax cable, that is referred to as the 'bus‘). The signal travels from one end of the bus to the other. A terminator is required at each to absorb the signal so as it does not reflect back across the bus. A media access method called CSMA/MA is used to handle the collision that occur when two signals placed on the wire at the same time. The bus topology is passive. In other words, the computers on the bus simply 'listen' for a signal; they are not responsible for moving the signal along.

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Created By : B. Sarangi, Sr. Lecturer

Created By : B. Sarangi, Sr. Lecturer

Created By : B. Sarangi, Sr. Lecturer.

Bus topology transmission

Created By : B. Sarangi, Sr. Lecturer

Advantages

• Failure of one of the station does not affect others.
• Good compromise over the other two topologies as it allows relatively high rate of data transmission.
• Well suited for temporary networks that must be set up in a hurry.
• Easy to implement and extend.

Disadvantages

• Require a network to detect when two nodes are transmitting at the same time.
• Does not cope well with heavy traffic rates
• Difficult to administer/troubleshoot.
• Limited cable length and number of stations.
• A cable brake can disable the entire network; no redundancy.
• Maintenance cost may be higher in the long run.
• Performance degrade as additional computers are added.

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Created By : B. Sarangi, Sr. Lecturer

Ring Topology

• A ring topology is a network topology or circuit arrangement in which each network device is attached along the same signal path to two other devices, forming a path in the shape of a ring.

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• Ring topology relays on well defined rules of transmission and reception in order to function smoothly. Nodes are connected in a definite series, with information going from one node to the next in a predefined order. Since each station is receives from the station before it and transmit to the station next to it.

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• Ring topology has a decreased distance sensitivity since each station regenerates the signal and it is easy to implement distributed control and checking facilities.

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• The most well known example of a ring topology is Token Ring.

Created By : B. Sarangi, Sr. Lecturer

Created By : B. Sarangi, Sr. Lecturer.

Created By : B. Sarangi, Sr. Lecturer Dept of Comp. Appln.

Advantages

• An orderly network where every device has access to the token and the opportunity to transmit

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• Under heavy network load performs better than a start topology.

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• To manage the connectivity between the computers it does not need network server.

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Disadvantages

• One malfunctioning workstation can throw away the entire network.

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• Moves, adds and changes of devices can affect the entire network .

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• It is slower than an Ethernet network.

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Created By : B. Sarangi, Sr. Lecturer

Star Topology

• Star Topology is the most common type of network topology that is used in homes and offices. In the Star Topology there is a central connection point called the hub which is a computer hub or sometimes just a switch. In a Star Network the best advantage is when there is a failure in cable then only one computer might get affected and not the entire network.
• The Star Network Topology typically needs more cable to be networked than the usual Bus topology. A common cable that is used in Star Network is the UTP or the unshielded twisted pair cable. Another common cable that is used in star networks is the RJ45 or the Ethernet cables.
• In a Star Network the entire network is dependant on the hub so if the entire network is not working then there could be a problem with the hub. This feature makes it easy to troubleshoot by offering a single point for error connection and at the same time the dependency is also very high on that single point.

Created By : B. Sarangi, Sr. Lecturer.

Created By : B. Sarangi, Sr. Lecturer

Created By : B. Sarangi, Sr. Lecturer

Created By : B. Sarangi, Sr. Lecturer.

Advantages

• A Star Network Topology is very easy to manage because of its simplicity in functionality.

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• The problems can be easily located logically in a Star Topology and therefore is easy to troubleshoot also.

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• The Star Topology is very simple in format so it is very easy to expand on the Star Topology.

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Disadvantages

• The Star Topology is fully dependant on the hub and the entire working of the network depends on the hub or the switch.

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• If there are many nodes and the cable is long then the network may slow down.

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Created By : B. Sarangi, Sr. Lecturer

Tree Topology

• Among all the Network Topologies we can derive that the Tree Topology is a combination of the bus and the Star Topology. The tree like structure allows you to have many servers on the network and you can branch out the network in many ways. This is particularly helpful for colleges, universities and schools so that each of the branches can identify the relevant systems in their own network and yet connect to the big network in some way.

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• Tree Structure suits best when the network is widely spread and vastly divided into many branches. Like any other topologies, the Tree Topology has its advantages and disadvantages. A Tree Network may not suit small networks and it may be a waste of cable to use it for small networks. Tree Topology has some limitations and the configuration should suit those limitations.

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Created By : B. Sarangi, Sr. Lecturer.

Advantages

• A Tree Topology is supported by many network vendors ad even hardware vendors.
• A point to point connection is possible with Tree Networks.
• All the computers have access to the larger and their immediate networks.
• Best topology for branched out networks.

Disadvantages

• In a Network Topology the length of the network depends on the type of cable that is being used.
• The Tree Topology network is entirely dependant on the trunk which is the main backbone of the network. If that has to fail then the entire network would fail.
• Since the Tree Topology network is big it is difficult to configure and can get complicated after a certain point.

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Created By : B. Sarangi, Sr. Lecturer.

Created By : B. Sarangi, Sr. Lecturer

Mesh Topology

• In this topology, every node has a dedicated point-to-point connection to every other node on the network. A fully connected mesh network has n(n-1)/2 channels to link ‘n’ devices. Therefore, every device on the network must have ‘n-1′ input/output (I/O) ports.
• In mesh network, each node is directly connected to all nodes on the network. This type of network involves the concept of routes. In this type of network, each node may send message to destination through multiple paths. It means that each node of mesh network has several possible paths to send (or to receive) message, but in Bus, Star, Ring and Tree topologies each node has only one path.

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Created By : B. Sarangi, Sr. Lecturer.

A fully connected mesh network

Created By : B. Sarangi, Sr. Lecturer.

Advantages

• It has multiple links, so if one route is blocked then other routes can be used for data communication.
• Each connection can have its own data load, so the traffic problem is eliminated.
• It ensures the data privacy or security, because every message travels along a dedicated link.
• Troubleshooting of this topology is easy as compared to other networks.
• Its performance is not affected with heavy load of data transmission.

Disadvantages

• It becomes very expensive because a large number of cabling and 110 ports are required.
• It is difficult to install.

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Created By : B. Sarangi, Sr. Lecturer

Hybrid Topology

• A hybrid topology is a combination of any two or more network topologies in such a way that the resulting network does not have one of the standard forms. For example, a tree network connected to a tree network is still a tree network, but two star networks connected together exhibit hybrid network topologies. A hybrid topology is always produced when two different basic network topologies are connected. A hybrid topology is always produced when two different basic network topologies are connected. Two common examples for Hybrid network are: star ring network and star bus network
• A Star ring network consists of two or more star topologies connected using a multistation access unit (MAU) as a centralized hub.
• A Star Bus network consists of two or more star topologies connected using a bus trunk (the bus trunk serves as the network's backbone).
• While grid networks have found popularity in high-performance computing applications, some systems have used genetic algorithms to design custom networks that have the fewest possible hops in between different nodes. Some of the resulting layouts are nearly incomprehensible, although they function quite well.

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Created By : B. Sarangi, Sr. Lecturer.

Created By : B. Sarangi, Sr. Lecturer