Logical Star Topology
In most practical networks that are based upon the partially connected mesh topology, all of the data that is transmitted between nodes in the network takes the shortest path between nodes. The network used a longer alternative path in the case of a failure or break in one of the links. This requires that the nodes of the network possess some type of logical 'routing' algorithm to determine the correct path to use at any particular time. Tree network topology Also known as a hierarchy network. The type of network topology in which a central 'root' node (the top level of the hierarchy) is connected to one or more other nodes that are one level lower in the hierarchy (i.e., the second level) with a point-to-point link between each of the second level nodes and the top level central 'root' node.
Bus logical topology is the most common logical solution for the bus, star, or star-wired bus physical topologies. This logics can be defined, as data from one device travels to all devices in this network. A star network is a topology of the local network where a central workstation is connected with each end-user computer or peripherals. A tree structure means that, the central nodes of these star networks are linked to a main cable (the Bus topology). So, a Tree network topology is a few Star networks connected into a Bus topology. A logical topology describes how network devices appear to be connected to each other. For example, in a logical diagram of your office network, you may show a connection between city A and city B.
In networks, each network interface controller has a unique (MAC) address—usually stored in the controller's permanent memory. To avoid address conflicts between network devices, the (IEEE) maintains and administers MAC address uniqueness. The size of an Ethernet MAC address is six. The three most significant octets are reserved to identify NIC manufacturers.
Bus A physical bus topology consists of a trunk cable with nodes either inserted directly into the trunk, or nodes tapping into the trunk using offshoot cables called drop cables. • In a logical bus topology, signals travel from one node to all other nodes on the bus.
A single cable, the backbone functions as a shared communication medium that devices attach or tap into with an interface connector. A device wanting to communicate with another device on the network sends a broadcast message onto the wire that all other devices see, but only the intended recipient actually accepts and processes the message. Ethernet bus topologies are relatively easy to install and don't require much cabling compared to the alternatives. 10Base-2 ('ThinNet') and 10Base-5 ('ThickNet') both were popular Ethernet cabling options many years ago for bus topologies.
However, if the central bus breaks down, so does the whole network, and it can be difficult to isolate the problem. Ring topology Nodes are connected in a circular pattern, and packets of information are sent through the ring until they reach their destination. Ring networks can outperform those based on the bus topology, and they can be easily reconfigured to add or remove devices.
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The terminating resistor prevents data reflections from coming across as data corruption. The bus is considered a multipoint system because all devices tap into the same. An important characteristic to remember in bus topologies is that all data signals are broadcast throughout the bus structure. In the following diagram, if node B sends a signal to node C, the signal propagates for the length of the cable and is seen by nodes A and D as well. It is necessary to have an addressing mechanism so that each node understands which messages it is to receive and which to ignore. Benefits of Bus topology Bus topology has the following advantage: • Cabling costs are minimized because of the common trunk. Disadvantages of Bus topology Disadvantages of bus topology are as follows: • Difficult to trouble shoot because no central distribution points exist.
Now you will examine two types of logical topologies. Logical topologies have the same names as physical topologies, but keep in mind that the physical topology describes the network you can see, whereas the logical topology describes the network from the viewpoint of the data traveling on the network. Networks can have different physical and logical topologies (most do!). The following two logical topologies are discussed in the following sections: • Ring logical topology• Bus logical topology Ring topologies function by passing data transmissions from one node to the next.
Firewalls are typically configured to reject access requests from unrecognized sources while allowing actions from recognized ones. The vital role firewalls play in network security grows in parallel with the constant increase in. Classification [ ] The study of network topology recognizes eight basic topologies: point-to-point, bus, star, ring or circular, mesh, tree, hybrid, or daisy chain. Point-to-point [ ].
• The second approach includes switching and routing functions where the central star coupler behaves as a frame-switching device. In this type, the central node buffers the arriving frame then retransmit it to the destination node. The star topology enables the high-speed data transfer especially when the central controller is utilized as a switch. Here the number of links is equal to the number of nodes. This topology is flexible and maintained efficiently, as compared to other topologies. Definition of Mesh Topology Mesh topology links the node in a way that each node is linked to the other node by a dedicated point-to-point link. Therefore, it creates n(n-1)/2 links to connect n number of nodes, which is a bit too much.
Compared to the bus topology, a star network generally requires more cable, but a failure in any star network cable will only take down one computer's network access and not the entire LAN. (If the hub fails, however, the entire network also fails.) See the illustration of Star Network Topology. Advantages of a Star Topology • Easy to install and wire. • No disruptions to the network then connecting or removing devices. • Easy to detect faults and to remove parts.
Logical network diagrams A logical network diagram describes the way information flows through a network. Therefore, logical network diagrams typically show subnets (including VLAN IDs, masks, and addresses), network devices like routers and firewalls, and routing protocols. In the Open Systems Interconnection (OSI) model, logical network diagrams correlate with the information contained in layer 3 (L3). Also known as the “network layer,” L3 is an abstraction layer that deals with packet forwarding through intermediate routers. Level 2 shows the data links between adjacent nodes, while level 1 shows the purely physical layout. Physical network diagrams A physical network diagram shows the actual physical arrangement of the components that make up the network, including cables and hardware. Typically, the diagram gives a bird’s eye view of the network in its physical space, like a floorplan.
Also, the tree topology is difficult to configure, wire, and maintain, especially in extensive networks. Figure 15: The tree topology is centrally controlled, making it easy to manage but highly vulnerable to single-point failure.
Network topology is the structure of a network and may be depicted physically or logically. It is an application of wherein communicating devices are modeled as nodes and the connections between the devices are modeled as links or lines between the nodes.
All messages are sent to all other devices connected to the hub. • An Ethernet network connected using a switch has a logical star topology.
Logical Star Topology Diagram
Extended star [ ] The extended star network topology extend a physical star topology by one or more repeaters between the central node and the (or 'spoke') nodes. The repeaters are used to extend the maximum transmission distance of the physical layer, the point-to-point distance between the central node and the peripheral nodes. Repeaters permit to reach a greater transmission distance beyond the transmitting power of the central node. The use of repeaters can also overcome limitations from the standard upon which the physical layer is based.
• If the backbone line breaks, the entire segment goes down. • More difficult to configure and wire than other topologies. 5-4-3 Rule A consideration in setting up a tree topology using Ethernet protocol is the 5-4-3 rule. One aspect of the Ethernet protocol requires that a signal sent out on the network cable reach every part of the network within a specified length of time.
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Communication between any two given devices is possible, but might require an intermediary connection. Full mesh topologies are usually impractical because the number of connections increases dramatically with every new node added to the network.
Logical Star
Ring Topology In a ring network, every device has exactly two neighbors for communication purposes. All messages travel through a ring in the same direction (either 'clockwise' or 'counterclockwise'). A failure in any cable or device breaks the loop and can take down the entire network. To implement a ring network, one typically uses FDDI, SONET, or Token Ring technology. Ring topologies are found in some office buildings or school campuses. See the illustration of Ring Topology. Bus Topology Bus networks (not to be confused with the system bus of a computer) use a common backbone to connect all devices.
Logical Topology A network's logical topology can also be referred to as its signal topology. This type of topology is not interested in how devices on the network are connected but how they communicate with each other. Logical topologies are created by the network protocols on NICs that determine the movement of data on the physical topology. Examples of these are: • Ethernet - logical bus topology • LocalTalk - logical bus or star topology • IBM Token Ring - logical ring. To add to this seeming confusion it may be the case that a network's logical topology is not always the same as its physical topology. Example 1: UTP Ethernet - A UTP Ethernet network operates logically as a bus but is organised by the devices connecting to a hub in a physical star Example 2: IBM's Token Ring - IBM's Token Ring operates as a logical ring but the devices are all connected to a hub-like device called a Multi-Station Access Unit (MSAU) which makes its physical topology a star.
This footprint is the 'cell' that gives cellular technology its name. Cellular providers are allotted a set of frequencies within a specified area called a metropolitan statistical area (MSA) or a rural statistical area (RSA) (usually, two providers obtain rights to the same MSA or RSA). They divide their statistical areas into cells and place an antenna at the center of each. Ideally, the antennas are located such that their entire allotted statistical area is covered by cells. In this way, a cellular user can move throughout the provider's statistical area and always be in range of an antenna. As the cellular user moves from one cell to another, the user's signal is transferred from one antenna to another in a process called 'handing off'.
The network operating system uses a network data protocol to communicate on the network to other computers. The network operating system supports the applications on that computer. 
A Network Operating System (NOS) includes Windows NT, Novell Netware, Linux, Unix and others. More Resources.
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Logical Star Topology
Alternatively, if the data does match the machine address, the data is accepted. Since the bus topology consists of only one wire, it is cheap to implement compared to other topologies. However, there is a higher cost of managing the network. Additionally, since only one cable is used, if the network cable breaks, the whole network will be shutdown Star. Star network topology In local area networks with a star topology, each network host (for example a PC) is connected to a central hub with a point-to-point connection. All traffic on the network passes through the central hub. The hub acts as a signal booster or repeater.