Difference between hub and spoke and star topology
Hubs and Switches in Star TopologiesIn this step, we will look at the role of a hub or a switch in a star network. 4.787 Reviews
In this step, we will look at the role of a hub or a switch in a star network.You will also learn more about how addresses and other fields are added to data that is sent, about the idea of encapsulation, and about how to build an Ethernet frame. The Ethernet HubIn the previous step you learned that bus topology was phased out in favour of star topology, which has a central connection point. Initially this was a hub. Each device connected to it using a dedicated UTP cable that linked into one of the hubs ports.On its way to the hub, a signal will have picked up some noise. As long as the noise does not cause the signal to cross a threshold level, the hub can recreate each bit, effectively removing the noise. This process is called regeneration. If there is too much noise, errors occur during regeneration: a binary 1 may be regenerated as a binary 0 or vice versa.CSMA/CDUnlike the wireless Aloha network, devices in a wired network can detect whether another device is transmitting data.Want to keeplearning?This content is taken from Raspberry Pi Foundation online course, An Introduction to Computer Networking for TeachersView Course FragmentationTo stop any one device hogging the wire by sending a large amount of data as one block, there is a rule that a device cannot send more that 1500 bytes of data in one go. Data larger than this must be split into smaller chunks that are sent separately this is called fragmentation. Fragmentation gives the other devices a chance to slot in their transmissions in between, thus ensuring fair access to all devices.Ethernet protocol, MAC addresses and framesA set of conventions and rules that govern the communications between devices is called a protocol. The 1500 byte limit, the CSMA/CD rules, and the need to send destination and recipient addresses are all part of the Ethernet protocol.
The four non-data fields together wrap around the data as the Ethernet Frame, in what is called encapsulation. Switch-based LANsUnlike an Ethernet hub, a switch learns the address of each device connected to its ports by looking at the source addresses in the Ethernet frames it receives. It then builds a table, mapping each device to the port it is connected to, so that it can switch incoming frames to the correct device by looking at the destination address in the incoming frame. If the destination address is not in the switchs table, the switch defaults to a hub behaviour and sends the frame out on all ports. Modern switches are capable of switching traffic between multiple ports simultaneously.Next upIn the next section, you will take a quiz to review what youve learned about connections, hubs, switches, and Ethernet frames.Questions
Want to keep learning?This content is taken from Raspberry Pi Foundation online course An Introduction to Computer Networking for TeachersView Course Share this postSee other articles from this course |