Network topology covers both the physical arrangement of devices and the logical flow of data across a network, and the two do not always match. Understanding the difference is essential for grasping how technologies like hubs, switches, and token ring actually function.
Network Topologies
Now there are different topology types, whether it be a tree or hub and spoke or point-to-point or a bus. There are different ways that we can create our networks, but we have to understand there's a physical way that we connect our devices, but then there's also a logical way of how our data actually flows, the communication that happens across it.
Here are some different topologies. We have the point-to-point, where a node is connected directly to another node. We also have here a bus set up, where we have these devices that are all communicating across the same line. We also have a tree that's set up here, a star or hub and spoke where there's a hub in the middle and there are spokes out here to the other nodes. There's a ring setup, which is set up in a ring formation. And then a mesh, where everything is connected to everything.
But we should understand, just because something is physically connected in some way, that's not how it functionally operates. That data flows a little differently.
For instance, we have a star or hub and spoke here where in the middle we have a switch and our devices are hanging off of that, but instead it could actually be communicating more like a bus. A good example of this is going to be a hub. A hub sits in the middle of your devices, and so all of your computers are connected from a physical standpoint to this hub right here. So we call this a star or hub and spoke. But from a communication standpoint, when one device communicates out, it gets sent across the line to all other devices. So from a logical perspective, or communication, or a data flow, that actually looks more like a bus, where one device talks and then all of the other devices are listening.
And the reason why this is important is we can see here how there's a flaw with how hubs work: now when one device is using this line, no other device can communicate on that same line. If they do, then we have a collision there. And so we can see here that physically how it looks and is set up is in one topology, a star topology, and how the communication happens looks different. The topology looks like a bus.
So now let's replace that hub with a switch. Now with a switch, physically it's set up like a star where all the devices are physically connected into that switch. And from a communication standpoint, it also is set up like a star, where each device sends the communication to the switch and then it can be sent out directly to the device it's communicating with, and then so on and so forth. So now a switch sets up a physical star, and from a communication point it looks like a star as well.
Token ring could be set up where physically it's set up as a bus. So all of these devices on here are interconnected, and when one device talks all other devices can hear that, and we know that bus is not an ideal way of setting things up, at least from a networking standpoint. So this is physically how it's set up. Now the problem is that all of these devices could end up talking at the same time.
So token ring sets out to solve this and says, well, let's do it where only one device can talk at one time. So maybe first it's this device, and then what happens is it switches to device two, and then device three gets a chance to talk, and then device one again, and then device two again, and then device three again. So from a communications point it does this round robin between those devices. We can look at that as being like a ring setup, hence the word token ring. And what happens is device one can talk, then two can talk, then three can talk, then four can talk, and so on and so forth. So physically this is set up as maybe a bus, but logically it communicates like a ring.
But that's not the only way we can set up token ring. Maybe we have a hub in the middle and then each device is stemmed off of this. It's very similar to the way the bus is communicating. So physically we're set up like this star right here, but from a communication standpoint it still communicates in that ring. Device one can talk, then device two can talk, then device three can talk, then device four can talk.
So really, what we're getting at is this physical setup could look different than this logical setup.
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