Topologies of Network Anil B Talawar What is
Topologies of Network Anil B. Talawar
What is a Topology? �Network topology is the arrangement of the various elements (links, nodes, etc. ) of a computer network. Essentially, it is the topologicalstructure of a network, and may be depicted physically or logically.
�Physical topology refers to the placement of the network's various components, including device location and cable installation, while logical topology shows how data flows within a network, regardless of its physical design. �Distances between nodes, physical interconnections, transmission rates, and/or signal types may differ between two networks, yet their topologies may be identical.
Main Types of Physical Topologies �The following sections discuss the physical topologies used in networks and other related topics. �Bus �Ring �Mesh �Star �Tree (Expanded Star)
Bus Topology �A bus topology is a type of network setup where each computer and network device is connected to a single cable or backbone. �Below, is a visual example of a simple computer setup on a network using the bus topology.
Advantages (benefits) of Linear Bus Topology 1)It is easy to set-up and extend bus network. 2) Cable length required for this topology is the least compared to other networks. 3) Bus topology costs very less. 4) Linear Bus network is mostly used in small networks. Good for LAN.
Disadvantages (Drawbacks) of Linear Bus Topology � 1) There is a limit on central cable length and number of nodes that can be connected. 2) Dependency on central cable in this topology has its disadvantages. If the main cable (i. e. bus ) encounters some problem, whole network breaks down. 3) Proper termination is required to dump signals. Use of terminators is must.
� 4) It is difficult to detect and troubleshoot fault at individual station. 5) Maintenance costs can get higher with time. 6) Efficiency of Bus network reduces, as the number of devices connected to it increases. 7) It is not suitable for networks with heavy traffic. 8) Security is very low because all the computers receive the sent signal from the source.
Ring topology �Alternatively referred to as a ring network, the ring topology is a computer network configuration where each network computer and device are connected to each other forming a large circle (or similar shape). �Each packet is sent around the ring until it reaches its final destination. �Today, the ring topology is rarely used. �Below is a visual example of a simple computer setup on a network using a ring topology.
�In Ring Topology, all the nodes are connected to eachother in such a way that they make a closed loop. �Each workstation is connected to two other components on either side, and it communicates with these two adjacent neighbors. �Data travels around the network, in one direction. �Sending and receiving of data takes place by the help of TOKEN.
Token Passing �Token contains a piece of information which along with data is sent by the source computer. �This token then passes to next node, which checks if the signal is intended to it. �If yes, it receives it and passes the empty to into the network, otherwise passes token along with the data to next node.
�This process continues until the signal reaches its intended destination. �The nodes with token are the ones only allowed to send data. Other nodes have to wait for an empty token to reach them. �This network is usually found in offices, schools and small buildings.
Advantages of Ring Topology � 1) This type of network topology is very organized. Each node gets to send the data when it receives an empty token. �This helps to reduces chances of collision. Also in ring topology all the traffic flows in only one direction at very high speed. � 2) Even when the load on the network increases, its performance is better than that of Bus topology.
� 3) There is no need for network server to control the connectivity between workstations. � 4) Additional components do not affect the performance of network. � 5) Each computer has equal access to resources.
Disadvantages of Ring Topology � 1) Each packet of data must pass through all the computers between source and destination. This makes it slower than Star topology. � 2) If one workstation or port goes down, the entire network gets affected. � 3) Network is highly dependent on the wire which connects different components. � 4) Network cards are expensive as compared to Ethernet cards and hubs
Mesh topology �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. �This topology is not commonly used for most computer networks as it is difficult and expensive to have redundant connection to every computer. �However, this topology is commonly used for wireless networks. Below is a visual example of a simple computer setup on a network using a mesh topology.
�In a mesh network topology, each of the network node, computer and other devices, are interconnected with one another. �Every node not only sends its own signals but also relays data from other nodes. �In fact a true mesh topology is the one where every node is connected to every other node in the network. �This type of topology is very expensive as there are many redundant connections, thus it is not mostly used in computer networks. It is commonly used in wireless networks. �Flooding or routing technique is used in mesh topology.
Types of Mesh Network topologies � 1)Full Mesh Topology: �In this, like a true mesh, each component is connected to every other component. �Even after considering the redundancy factor and cost of this network, its main advantage is that the network traffic can be redirected to other nodes if one of the nodes goes down. �Full mesh topology is used only for backbone networks.
� 2) Partial Mesh Topology: �This is far more practical as compared to full mesh topology. �Here, some of the systems are connected in similar fashion as in mesh topology while rests of the systems are only connected to 1 or 2 devices. �It can be said that in partial mesh, the workstations are ‘indirectly’ connected to other devices. This one is less costly and also reduces redundancy.
Advantages of Mesh topology � 1) Data can be transmitted from different devices simultaneously. This topology can withstand high traffic. � 2) Even if one of the components fails there is always an alternative present. So data transfer doesn’t get affected. � 3) Expansion and modification in topology can be done without disrupting other nodes.
Disadvantages of Mesh topology � 1) There are high chances of redundancy in many of the network connections. � 2) Overall cost of this network is way too high as compared to other network topologies. � 3) Set-up and maintenance of this topology is very difficult. Even administration of the network is tough.
Star Topology �Alternatively referred to as a star network, a star topology is one of the most common network setups where each of the devices and computers on a network connect to a central hub. �A major disadvantage of this network topology is that if the central hub fails, all computers connected to that hub would be disconnected. �Below is a visual example of a simple computer setup on a network using the star topology.
�A star topology is designed with each node (file server, workstations, and peripherals) connected directly to a central network hub, switch, or concentrator. �Data on a star network passes through the hub, switch, or concentrator before continuing to its destination. �The hub, switch, or concentrator manages and controls all functions of the network. It also acts as a repeater for the data flow. �This configuration is common with twisted pair cable; however, it can also be used with coaxial cable or fiber optic cable.
Fiber Optic Cable
Advantages of a Star Topology �Easy to install and wire. �No disruptions to the network when connecting or removing devices. �Easy to detect faults and to remove parts.
Disadvantages of a Star Topology �Requires more cable length than a linear topology. �If the hub, switch, or concentrator fails, nodes attached are disabled. �More expensive than linear bus topologies because of the cost of the hubs, etc.
Tree or Expanded Star �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.
�Alternatively referred to as a star bus topology, tree topology is one of the most common network setups that is similar to a bus topology and a star topology. �A tree topology connects multiple star networks to other star networks. �Below is a visual example of a simple computer setup on a network using the star topology.
Advantages of a Tree Topology �Point-to-point wiring for individual segments. �Supported by several hardware and software venders.
Disadvantages of a Tree Topology �Overall length of each segment is limited by the type of cabling used. �If the backbone line breaks, the entire segment goes down. �More difficult to configure and wire than other topologies.
Considerations When Choosing a Topology �Money. A linear bus network may be the least expensive way to install a network; you do not have to purchase concentrators. �Length of cable needed. The linear bus network uses shorter lengths of cable. �Future growth. With a star topology, expanding a network is easily done by adding another concentrator. �Cable type. The most common cable in schools is unshielded twisted pair, which is most often used with star topologies.
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