What are computer networks and their uses?
Friends, this is the first part of our article on Computer Networks.
Today we’re going to do the introduction to computer networks by talking about layer one devices, and layer two devices. And then we’re going to conclude with layer three devices.
There’s a fair amount of information to cover. So let’s go ahead and dive into this session. Of course, I’m going, to begin with, layer one devices. Well, before I start talking about the layer one devices, we need to talk about the open system interconnection model.
The OSI model was developed as a way to help disparate computing systems to communicate with each other. The OSI reference model has seven layers. Layer one is the physical layer, layer two is the data link.
Layer three is the network layer. and four is the transport layer five is the session. Layer Six is the presentation and layer seven is the application. We’re going to be discussing the bottom three layers and going to give examples of computer networks. Also, we are going to discuss how computer networks work? These are layers one, two, and three today.
OSI Model:
Now, most devices do function at more than one layer of the OSI reference model. But when it comes time to determine where they fit into the model, you must first determine the highest level at which they operate, because that’s where they fit into the OSI model.
To do that, you must know what they do and how that relates to the OSI model. And with that, let’s talk about analogue modems. The word modem is actually derived from a contraction of modulator-demodulator.
Modems were developed to take a digital signal coming from a digital node and convert it to an analogue signal modulating the signal and placing it on a wire. In return, it would accept an analogue signal from the wire and convert it demodulating the signal back to a digital signal that the node can understand.
Modems:
Modems were developed to create a connection between network segments via the public switched telephone network using the plain old telephone system. Now modems provide for a single connection to a network. And they’re only concerned about the wire in the wire residing on the physical layer, layer one of the OSI model.
It doesn’t care where the signal comes from, it just does its job. Then there’s the hub. A hub functions as a concentrator or repeater in that it doesn’t care where the signal comes from, or where the signal is going. Kind of like the modem, it takes an electrical signal that arrives on a port and replicates that signal out all of its other ports.
Hub may have just a few ports, or it may have many ports for a variety of reasons the hub is not very common anymore in the modern network.
So now let’s move on to layer two devices. The first layer of the two devices that we’re going to talk about is the switch. A switch utilizes an application-specific integrated circuit chip and a basic chip. The ASIC chip has specific programming that allows the switch to learn when a device is on the network and which ports it is connected to via that device’s layer two MAC addresses.
That’s what makes a switch a layer two device, a switch may have just a few ports or it may have many ports, kind of like the hub. And although a switch is smarter than a hub, it can still be very simple, or it can be highly complex and programmable. A switch can only communicate with local network devices.
Another layer two devices that we need to talk about is our wireless access points. The WHAP is a specific type of Network Bridge that connects or bridges, wireless network segments with wired network segments.
Network Bridges:
The most common type of web bridge and 802.11 wireless network segment with an 802.3 Ethernet network segment just like a switch a wire Access Point will only communicate with local network devices.
Now let’s move on to layer three devices. And first up is the multi-layer switch. A multi-layer switch provides normal layer two network switching services, but it will also provide layer three or higher OSI model services. The most common multi-layer switch is a layer three switch, it not only utilizes a sync chip for switching but a sync chip is also programmed to handle routing functions.
This allows the device to communicate and pass data to non-local network devices. A multi-layer switch is a highly programmable and complex network device. A multi-layer switch may have just a few ports, or it may have a lot of ports.
They’re not very common in the small office home office network. Because they’re really expensive, you’re more likely to find them in an enterprise local area network. Now let’s move on to the router. A router is the most common network device for connecting different networks together, utilizing the OSI models layer three logical network information.
That’s what makes a router a layer three device. The router uses software programming for decision-making, as compared to the switch’s use of an ASIC chip. The router uses this programming to keep track of different networks in what it considers to be the best possible route to reach those networks.
A router can communicate with both local and non-local network devices. In most cases, a router will have fewer ports, than a switch. Now that concludes this session on the introduction to network devices. In part one, we learn about layer one devices. We learn about layer two devices.
And we concluded with a couple of layer three devices. In the next article which is going to be part two on Computer Networking, we will be going to discuss GSM and CDMA networks.
That’s enough for today’s article, for more stay tuned and read our next article.
You can also read our other articles.