Identifying Network Topologies

A network topology is the physical layout of computers, cables, and other components on a network. There are a number of different network topologies, and a network may be built using multiple topologies. The different types of network layouts are :

  • Bus topology
  • Star topology
  • Mesh topology
  • Ring topology
  • Hybrid topology
  • Wireless topology

Bus Topologies

  • A bus topology uses one cable as a main trunk to connect all of the systems together.
  • A bus topology is very easy to set up and requires no additional hardware such as a hub.
  • The cable is also called a trunk, a backbone, or a segment.
  • With a bus topology, when a computer sends out a signal, the signal travels the cable length in both directions from the sending computer.
  • When the signal reaches the end of the cable length, it bounces back and returns in the direction it came from. This is known as signal bounce.
  • Signal bounce is a problem, because if another signal is sent on the cable length at the same time, the two signals will collide and
  • be destroyed and then must be retransmitted.
  • For this reason, at each end of the cable there is a terminator.
  • The terminator is designed to absorb the signal when the signal reaches the end, preventing signal bounce.
  • If there is no termination, the entire network fails because of signal bounce, which also means that if there is ever
  • a break in the cable, you will have unterminated ends and the entire network will go down
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  • Advantages of a Bus Topology
    • One advantage of a bus topology is cost
      • A bus topology uses less cable than a star topology or a mesh topology.
      • and you do not need to purchase any additional devices such as hubs.
    • Another advantage of a bus topology is the ease of installation.
      • With a bus topology, you simply connect the workstation to the cable segment or backbone
  • Disadvantages of a Bus Topology
    • The main disadvantage of a bus topology is the difficulty of troubleshooting it.

Star Topologies

  • In a star topology, all computers are connected through one central device known as a hub or a switch, as illustrated in below Figure . Each workstation has a cable that goes from the network card to the hub device.
  • One of the major benefits of a star topology is that a break in the cable causes only the workstation that is connected to the cable to go down, not the entire network, as with a bus topology. Star topologies are very popular topologies in today’s networking environment
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  • Advantages of a Star Topology
    • One advantage of a star topology is scalability and ease of adding another system to the network.
    • If you need to add another workstation to the network with a star topology, you simply connect that system to an unused port on the hub.
  • Disadvantages of a Star Topology
    • if the hub fails in a star topology, the entire network comes down, so we still have a central point of failure. But this is a much easier problem to troubleshoot than trying to find a cable break with a bus topology.
    • Another disadvantage of a star topology is cost. To connect each workstation to the network, you will need to ensure that there is a hub with an available port, and you will need to ensure you have a cable to go from the workstation to the hub. Today, the cost is increasingly less of a disadvantage because of the low prices of devices such as hubs and switches

Mesh Topologies

  • A mesh topology is not very common in computer networking today,
  • In a mesh topology, every workstation has a connection to every other component of the network,
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Ring Topologies

  • In a ring topology, all computers are connected via a cable that loops in a ring or circle.
  • a ring topology is a circle that has no start and no end. Because there are no ends, terminators are not necessary in a ring topology.
  • Signals travel in one direction on a ring while they are passed from one computer to the next, with each computer regenerating the signal so that it may travel the distance required.
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  • Advantages of a Ring Topology
    • A major advantage of a ring topology is that signal degeneration is low because each workstation is responsible for regenerating or boosting the signal.
  • Disadvantages of a Ring Topology
    • The biggest problem with ring topologies is that if one computer fails or the cable link is broken, the entire network could go down. With newer technology, however, this isn’t always the case.

Hybrid Topologies

It is important to note that it is typical for networks to implement a mixture of topologies to form a hybrid topology. For example, a very popular hybrid topology is a star-bus topology, in which a number of star topologies are connected by a central bus. This is a popular topology because the bus will connect hubs that are spread over distance.

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Wireless Topologies

  • A wireless topology is one in which few cables are used to connect systems.
  • The network is made up of transmitters that broadcast the packets using radio frequencies.
  • The network contains special transmitters called cells, or wireless access points, which extend a radio sphere in the shape of a bubble around the transmitter.
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  • This bubble can extend to multiple rooms and possibly floors in a building.
  • The PCs and network devices have a special transmitter-receiver, which allows them to receive broadcasts and transmit requested data back to the access point.
  • The access point is connected to the physical network by a cable, which allows it, and any wireless clients, to communicate with systems on the wired network.

  • Point-to-Point and Point-to-Multipoint

There are two popular layouts for topologies: they are either point-to-point or pointto-multipoint. A point-to-point topology—also known as host to host—is one system connected directly to another system. In the past these systems would connect directly through the serial ports with a null modem cable, but these days, you could connect them using a crossover cable or a wireless connection.

A point-to-multipoint topology uses a central device that connects all the devices together. This topology is popular with wireless. With point-to-multipoint, when the central device sends data, it is received by all devices connected to the central device. But if one of the devices that are connected sends data, then it is received by only the destination system.

Segments and Backbones

With the various topologies you’ve looked at, you have seen the words segment and backbone mentioned a couple of times. A network segment is a cable length (or multiple cable lengths) that is uninterrupted by network connectivity devices, such as bridges and routers. It is typical that a single network may be broken into multiple network segments through the use of a bridge or router to cut down on network traffic,

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