In a star topology, what happens when a workstation loses its physical connection to another device

A star network is a local area network (LAN) topology in which all nodes -- personal computers (PCs), workstations or other devices -- are directly connected to a common central computer that is often referred to as a hub.

Andrew Froehlich, West Gate Networks

Table of Contents Show

  • Ch 1. chapter review
  • star network
  • A star network is a local area network (LAN) topology in which all nodes -- personal computers (PCs), workstations or other devices -- are directly connected to a common central computer that is often referred to as a hub.
  • What is a star network?
  • How does a star network work?
  • Comparing star network topologies with other topologies
  • Network Fundamentals
  • Peer-to-Peer
  • DID YOU KNOW?
  • EXAM WARNING

10 Aug 2021

What is a star network?

A star network is a local area network (LAN) topology in which all nodes -- personal computers (PCs), workstations or other devices -- are directly connected to a common central computer that is often referred to as a hub. Therefore, a star network is often referred to as a hub-and-spoke network topology.

Every workstation connected to the hub is indirectly connected to each workstation using the hub as an intermediary device. Star networks are typically deployed at the access layer of enterprise networks. The access layer uses a centralized network switch to connect all endpoints to the rest of the LAN.

This image shows the central hub of a star network and all of its interconnecting devices.

This graphic shows a star network consisting of a central hub. Each workstation is shown as a PC or laptop with the central hub interconnecting all devices. The lines that interconnect endpoint PCs and laptops are the spokes of the star topology. In the real world, a star network can consist of either wired or wireless connections. In this specific case, each spoke is connected to a hub by a wired connection.

How does a star network work?

Because a star network uses a centralized hub, that hub is responsible for controlling communications between devices. However, there are different ways that a central hub can manage these communications. For example, an Ethernet hub is a network device that simply listens to a communication destined for a device on a different spoke and then retransmits -- or broadcasts -- the message out to all spokes. This is the simplest form of a network hub, as it only must repeat the message to all other connected spokes. But this method can become inefficient quickly, as each communication is sent out to all spokes, as opposed to only the spoke the message was intended for.

If too many devices begin communicating on a network hub, the amount of broadcast traffic can quickly reduce network throughput. It also places the Ethernet hub where it physically looks like a star network topology but operates like a traditional bus network topology.

An Ethernet switch, on the other hand, may look like an Ethernet hub from a physical cabling perspective, but it is far more sophisticated when it comes to how the centralized device handles the transmission of communications to the intended spoke device. Ethernet switches eliminate the need to broadcast communications out to all spokes on the star network. Instead, the Ethernet switch maintains a media access control (MAC) address table. This table statically or dynamically maps the physical MAC address to the port or spoke where the spoke endpoint resides. Therefore, if an Ethernet switch knows the MAC address and specific spoke that the MAC address lives on, it can use this information to send a communication directly out to a single spoke, as opposed to broadcasting the communication to all spokes -- unnecessarily using network bandwidth. Ultimately, an Ethernet switch accomplishes the same goal as an Ethernet hub with the added benefit of better network transport efficiency.

Comparing star network topologies with other topologies

The star network topology works well when workstations are deployed randomly throughout a building or facility. With the hub-and-spoke design, it is easy to add or remove workstations, as all cabling is pulled and connected to a central hub.

From a cabling perspective, if the workstations are reasonably close to the vertices of a convex polygon and the system requirements are modest, the ring network topology may serve the intended purpose at a lower cost than the star network topology. If the workstations lie nearly along a straight line, the bus network topology may be best.

In a star network, a cable failure on a single spoke will only affect the spoke endpoint that it links to the central computer. All the other workstations will continue to function normally with the exception that they will not be able to communicate with the device that resides on the failed spoke. In other words, a star network is powerful from this perspective, as a failure on one spoke does not affect communications of other spokes that are in a functioning state. However, the caveat is that, if the central hub were to fail, all spokes on the star network also fail. If any workstation goes down, none of the other workstations will be affected. Therefore, if network redundancy is required, a mesh network topology may be a preferable option.

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Related Terms

  • full-duplex
  • patch panel
  • route summarization (route aggregation)

Network Fundamentals

Naomi J. Alpern, Robert J. Shimonski, in Eleventh Hour Network+, 2010

Peer-to-Peer

In a peer-to-peer network, computers on the network are equal, with each workstation providing access to resources and data. This is a simple type of network where computers are able to communicate with one another and share what is on or attached to their computer with other users. It is also one of the easiest types of architectures to create. Here are some of the characteristics of a peer-to-peer network:

Individual users have responsibility over who can access data and resources on their computers.

Operating systems such as Windows XP and Windows Vista allow accounts to be set up that will be used when other users connect to an individual user's computer.

Accounts, passwords, and permissions are saved in a local database and are used to determine what someone can do when connecting to your computer.

DID YOU KNOW?

One important issue with peer-to-peer networks is security. Each computer on this type of network may allow or deny access to other computers, as access to data and resources is controlled on each machine. For example, a user could share a folder containing payroll information on his or her computer, allowing other users to access the files in that folder. Because users can control access to files and resources on their computers, network administration isn't controlled by one person. As such, peer-to-peer networks are generally used in small deployments and in situations where security isn't a major concern, as in the case of home networks or small businesses.

EXAM WARNING

A peer-to-peer network is decentralized, because resources and administration are handled locally on each participating machine, while a client/server network can be either centralized or decentralized. Remember the differences and relationships between different network types for the exam, as they may be covered either directly or incorporated in the scenarios used to cover other material.

What is the consequences if a connection fails in star topology?

In star topology, the central site plays an important role; if it fails, all the connections will go down. Performance of the central hub dictates the performance of the connection.
However, relying on one cable does mean that bus topologies have a single point of failure. If the cable fails then the entire network will go down.

How are devices connected in a star topology?

A star network is a local area network (LAN) topology in which all nodes -- personal computers (PCs), workstations or other devices -- are directly connected to a common central computer that is often referred to as a hub. Therefore, a star network is often referred to as a hub-and-spoke network topology.