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Even if it was running at only 10 Mbps

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provides a full 10 Mbps to the PC connected to the port.

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In other words PC A gets a full 10 Mbps

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rather than sharing that bandwidth with other devices.

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That’s very different to the 0.75 Mbps we had when we were using a hub.

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10 Mbps is dedicated on individual ports rather than being shared between devices.

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So if you add more devices on the switch

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it doesn’t degrade the throughput that each device gets.

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In addition you can increase the speed by changing the duplex.

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So by setting this to full duplex you actually get 20 Mbps

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hubs operated by using CSMA/CD which is very similar to 10base2.

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with shared bandwidth they are collisions whereas

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with a switch when full duplex is enabled it means that you can send

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and receive traffic at the same time.

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Half duplex communication is like a walky talky

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where only one side can send at any given time.

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So one party would say "Hello! How are you?" over

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and over is used to indicate to the other party that they can speak.

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The other party would then say something and end with the word over.

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So that the first party could say something.

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The moral of the story is that only one party can transmit at any given time

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if both parties try to transmit at the same time,

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there’ll be a collision that’s half duplex.

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Full duplex communication on the other hand is like a landline telephone

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where you can speak and listen at the same time.

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Landline telephones use full duplex so both parties can speak

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and listen simultaneously whereas walkie talkies are half duplex devices

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where one party can transmit and the other party needs to receive.

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Walkie talkies only one person can speak at a time

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landline telephones both parties can speak at the same time.

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Walkie talkies as an analogy are half duplex, landline telephones are full duplex.

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Hubs once again use Carrier Sense Multiple Accesses Collision Detection

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in other words half duplex where only one party can transmit at any given time.

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An individual port on a switch however, you can set those ports to use full duplex

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which means that both the switch and the PC

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can transmit and receive at the same time.

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Just be aware however that when you enable full duplex,

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collision detection is turned off because the devices operate on that premise

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that they can send and receive at the same time.

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So there’s no need to have collision detection because no collections will take place.

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That will cause issues however where 1 side is set to full duplex

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and the other side is set to half duplex.

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It is important that full duplex be enabled on both sides

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if you wanna use full duplex.

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But once again in this example if full duplex is enabled

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rather than only having 10 Mbps in theory you can increase that to 20 Mbps

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because both parties can transmit and receive at the same time.

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So by just replacing a hub with a switch

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we can increase the throughput of of this network from 0.75 Mbps to 20 Mbps

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all we did was replace the hub with the switch and enabled full duplex.

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Now full duplex is often negotiated automatically between devices.

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So the switch and the PC will negotiate to use full duplex

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if they both support it and will hopefully choose correctly.

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In networks it does happen that 1 side chooses full duplex

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and the other side chooses half duplex.

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And that’s gonna cause a lot of problems on that link.

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So if users complaining about slow throughput

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check the duplex on both sides and check that it’s been negotiated correctly

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because it may have negotiated incorrectly.

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Speed by the same token can also negotiated between a switch in a PC

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and that could also be incorrectly negotiated.

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These days PCs tends to have gig ports

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and thus the bandwidth can increase

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from 0.75 Mbps when using a hub to 2 gigabits per second

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The throughput of switches is much, much greater than hubs

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and therefore switches are preferred today

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over other devices like hubs or bridges.

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Be aware however that in wireless networks

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access points tend to operate like hubs

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which have a shared infrastructure which therefore means

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shared bandwidth where as with switches devices have dedicated bandwidth.

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So in summary a switches a layer 2 device in the OSI model

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it operates at the data link layer.

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Switches have major advantages when compared with hubs

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and bridges and that’s to do with the throughput

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and scalability of networks using switches.

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Switches process frames in hardware rather than in software

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and can therefore process frames at wire speed

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as well as supporting many more ports than bridges and hubs.

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These days switches can also operated layer 3, hence the term layer 3 switches.

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But for the moment we're just talking about pure layer 2 switches.

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We'll know discuss routers and then we can talk about layer 3 switches.