0:00:02.080,0:00:03.919
When you're designing, building, or

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troubleshooting a network, you'll be

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using a network topology type that can

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vary depending on the technology you're

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using. If you're looking to understand

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the way the data is flowing, or you want

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to plan to create a new type of network,

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then it's useful to understand what

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these topologies might be. This is also

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useful during the troubleshooting

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process because you'll know exactly what

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flow the traffic takes to get between

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point A and point B. One of the most

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popular types of topologies is the star

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topology. You might also hear this

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referred to as a hub and spoke, where the

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hub is in the middle and the spokes are

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along the outside. This is a topology

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that you'll find on almost any network,

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regardless of the size of the network.

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And you'll also find that most devices

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are connecting back to this central hub

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of the star. For example, a switched

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Ethernet network has the Ethernet switch

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in the middle of this star. And then all

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of the devices run directly back to this

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particular switch. They're not connecting

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to each other. They're instead connecting

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back to the central switch in this star

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topology.

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Although we don't often see a ring

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topology used on our local area networks,

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it's still a topology type that's used

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quite often for wide area networks. So

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although many people will remember the

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older Token Ring technologies that we

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used to run inside of our local area

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networks, we don't generally find those

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ring networks any longer. But if you're

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connecting over a metropolitan area

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network or a wide area network, we use

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ring networks extensively. It's not

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because a ring technology somehow lends

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itself to work better over a wide area

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network. It's because we can create

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additional redundancy using the ring

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topology.

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For example, a very common way to send

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traffic over a ring network is to have

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the traffic simply go in a circle. Now, if

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we're on this wide area network and

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there's construction going on and

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someone happens to sever a fiber

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connection that's being used for this

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metropolitan area network, then we're not

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going to be able to send that traffic

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through the rest of that ring. But the

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devices that are on either side of that

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severed link recognize that traffic is

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no longer able to traverse that

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connection, and instead will loop back

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the connection on those individual

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endpoints. So instead of having data go

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around a ring, the data will instead go

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as far as it can around the ring and

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then loop back to get to the other side

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of the ring, maintaining uptime and

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availability even in the case where part

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of that ring may be severed.

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Early types of Ethernet networks were

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not switched Ethernet, but were instead

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run over coax. And this coax was quite

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simply a cable that was run down the

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middle of the room, very similar to this

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cable. This is a bus network. And although

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it was commonly used on those early

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Ethernet networks, we can still find

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modern networks that use the same bus topology.

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One problem with bus networks is that it

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is a single cable that is running either

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through the walls or down the center of

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the room. And if we happen to have a

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break in this cable, you can see

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immediately that it would suddenly

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segment the network into different

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pieces, or in some cases, cause no data to

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be transferred across the network. That's

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one of the reasons we moved away from

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bus networks for our local area networks--

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because one single disconnect could

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cause an outage for everybody else on the network.

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In our modern automobiles, we have bus

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networks that we use extensively. These

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are Controller Area Network buses, or CAN

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bus connections, and they're used to

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connect all of the different sensors and

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controllers inside of our automobiles to

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be able to make all of our cars much

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safer to drive on the roads.

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Another popular topology, especially in

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larger networks, is to create a mesh

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between devices or a mesh between sites.

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We may have devices that are connected

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in different locations, and we might want

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to connect them all together. But instead

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of having a single connection to a

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particular site, we may want to create

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multiple connections to mesh these

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together. That way, if we do lose any one

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of these network links, we're able to

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work around that problem by simply using

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one of the redundant connections.

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You'll commonly use this type of mesh

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design if you're creating redundancy or

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fault tolerance, or perhaps you're

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designing a load-balanced network and you

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can use different parts of the network

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to share that load.

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Probably the most common place to find a

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wired mesh network is over a wide area

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network, where you can create multiple

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links to other sites so that you can

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have a primary connection from one site

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to the other, and then a backup or

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secondary connection that you can use if

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you run into problems.

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When you start combining these different

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topologies together, you create a hybrid

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network. A hybrid network is more than

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one of these topology types all working

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together. For example, you might have

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three remote sites all connecting

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devices together using a switched

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Ethernet or star network. And then you

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may be connecting those together over a

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wide area network that uses a ring topology.

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If you're using a wireless network, you

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may be communicating in a number of

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different ways. If you're using an access

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point, you're probably communicating over

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an infrastructure connection. This means

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that all of the devices on your network

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are communicating through an access

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point. This is probably the most common

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way to use wireless connections, but it's

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not the only way to communicate over a

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wireless link. If you just have two

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devices and there's no access point that

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you can use, you can connect directly

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from one device to another using ad hoc

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networking. You don't need an access

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point or any other type of wireless

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infrastructure. You simply have

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one device communicate directly to another

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device over this wireless connection.

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And if you've added Internet of Things

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devices, which are commonly wireless

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devices that control our lights, our door

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locks, or the air conditioning systems,

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then you're probably using a mesh

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network where all of these devices can

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communicate to all the other devices

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simultaneously to create an

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interconnected mesh of communication

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between all of these IoT devices.

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One of the advantages of these mesh

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wireless networks is that it allows many

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devices to communicate to each other,

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even if those devices are very far apart

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from each other. This also allows the

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mesh network to self-heal. So if you turn

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off one of those IoT devices, the

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remaining devices will self-heal and

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redesign themselves into a mesh network

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that will allow them to continue the communication.