Devices that provide this functionality are known as

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Devices that provide this functionality are known as a central connecting point and they are the backbone of most network infrastructures. The job of the central connecting point is to manage the flow of data that is being transmitted between all the connected hosts on the network. There are two types of devices that function as a central connecting point. Hub 3:22-4:30 The first is called a hub. Hubs are the most basic type of central connecting device. They offer very little functionality beyond connecting devices together. In fact, they do a very poor job of managing the flow of data. This is due to the way hubs function. Let's say this computer needs to send information to this computer here, so it sends that information to the hub. When the hub receives this information it knows it needs to send it to another computerbut it has no idea which computer it needs to go to. Hubs don't know any information about the computers that are connected. Because of this, the hub copies the information and sends it out on every single port.
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Each computer connected to the hub then looks at the information. If it's addressed to it, then it processes it. If it's not, then the computer discards it. With three computers, this functionality might work. However, as more computers are added to the hub the amount of information that needs to be sent increases. This creates a huge bottleneck at the hub. Because of this, modern networks instead use switches, which are the second type of connecting device. Switch 4:31-6:04 Switches look very similar to hubs. However, they function very differently. Unlike hubs, switches known which host is connected to each port. By knowing this information switches are able to create what's called a packet switch network. When information is sent from one computer to another, the switch looks at the data, determines which host it's addressed to based on the mac address, and sends it out to that host port only. By directing traffic like this, not only do switches eliminate the bottleneck problem but they allow the network to operate in full duplex mode. See, networks can operate in two different modes, half duplex and full duplex. When operating in half duplex mode, devices can either send data or receive data but not both at the same time. This is the mode that hub-based networks use. Like its name suggests, half duplex mode cuts network bandwidth in half. Switches, on the other hand, operate in full duplex mode and this means that devices can send and receive data at the same time, utilizing the entire network bandwidth. You can think of half and full duplex as a two-way radio on a telephone. When using a two-way radio only one person can be talking at a time, the other person can only listen. However, when using a telephone both parties can be listening and talking at the same time.
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  • Spring '14
  • Computer network, Local area network, Network topology, Metropolitan area network

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