Internet connectivity is important for many people, and fortunately there are many ways to get connected. In this video, you’ll learn about cable modems, DSL, dialup networks, fiber connectivity, satellite networking, ISDN, cellular networks, and line-of-sight services.
One of the more popular internet connection types these days is on a cable modem. This is a network that originally was a video network. But we were able to use those same coax lines to run data communication using these cable modems.
This uses a standard called DOCSIS. DOCSIS stands for Data over Cable Service Interface Specification. It allows us to send data over these networks, anywhere from four megabits through 250 megabits and even higher with the newer DOCSIS standards. We often will see data, video, and voice communication running over these cable modem networks.
Another popular internet connection type is one that also used a set of existing wires that was coming into our businesses and into our homes. This is DSL, or more specifically, ADSL– asymmetric digital subscriber lines. It uses the existing telephone lines that are coming into our homes.
And the reason it’s asymmetric is because the download speed on these networks is usually faster than the upload speed. And so therefore, it’s not a symmetric or identical amount of speeds. It’s asymmetric. Usually, there’s a distance limitation to these networks. Generally, it’s somewhere around 10,000 foot limitation from the central office.
If your wiring is going to go farther than that to your home, you may not be able to have DSL service. These days, we generally see speeds for DSL that’s 24 megabit down, and 3.3 megabit upstream. But there are other standards along these lines that will increase the speeds even further. One of these is VDSL, or very-high-bit-rate DSL, where you can get a three megabit through 100 megabit download speeds.
Before we had DSL, we were running our network communications over those phone lines using a dial-up configuration. These allowed us to take the same connections we were using for voice and instead send digital signals over these networks. The speeds, however, were relatively small. You had 56 kilobit modems. But with compression, you could sometimes get a throughput that approached 320 kilobits per second.
So obviously, this is relatively slow when you compare it to the megabit speeds that you get with DSL or cable modem configurations. And because this is such a slow throughput and we had to have a separate phone line for every connection, it did not scale very well. However, if you’re in a location that doesn’t have a cable modem, it doesn’t have DSL connectivity, and you need to transfer just a little bit of information during the day, this may be useful to have, especially on Legacy systems that were designed around these dial-up networks.
The latest trend in internet connectivity is to bring the fiber directly to you. So we’ll connect to your home or your business directly, allowing you to run internet connections, voice communication, and video over this single fiber optic connection. And the speeds for fiber optic are much improved over these older technologies. You generally get 100 or more HD channels. There could be one gigabit per second internet access with a terabyte of cloud storage and two terabyte DVRs. Because you have so much bandwidth available, you really have a larger number of services that are now available to you.
There may be some cases where you don’t have access to a cable modem network, you’re too far to run DSL, and maybe a phone line communication is just too slow. So in those cases, you might want to consider using a satellite network. This is a non-terrestrial communication. You are communicating directly to a satellite and then back down to earth to be able to have internet connectivity.
This obviously is a little more expensive than a cable modem or a DSL connection, but you still get pretty good speeds. These days, you can get about 15 megabits down and two megabits up when you’re working on a satellite network. Because you’re going all the way up to space and back down again, however, you generally have high latency.
So you’ll see that the latency just to go up to the satellite is about 250 milliseconds and another 250 milliseconds to come back down. So it’s half a second every time you send information back and forth over this non-terrestrial link. So you want to be sure the applications you’re using can tolerate this much slower network communication.
These connections between the ground station and the satellite itself are usually running frequencies in the two gigahertz range. This works over a line of sight communication. And it’s very sensitive to anything that might be in the way. If you have rain that’s coming through, you may have what we call rain fade that temporarily disrupts the communication link between the ground and the satellite.
Another type of niche networking would be ISDN. It stands for Integrated Services Digital Network. You often see ISDN packaged and delivered in two different ways. One, called a basic rate interface, or a BRI. You may see this described as 2B plus D. The B channels are called bearer channels. These are the channels that are actually sending the data through the network. And with BRI, you get two 64 kilobit bearer channels.
You also have one channel that is the signaling channel, or the management channel for ISDN. And for BRI, there is one 16 kilobit D channel. The other type of ISDN is called PRI, or primary rate interface. This is one that is usually delivered over a T1 or E1 lease line. This is something on a T1 where you’re getting 23 bearer channels and one of the channels is set up as that D channel for control.
In an E1, which is usually seen in Europe, we have 30 bearer channels, one single D channel, and a separate alarm channel. These days, we don’t generally see ISDN being used in a home. We usually have a DSL or cable modem or even fiber to our homes. But in larger organizations where you have a lot of legacy phone systems, you may still see a number of ISDN PRI connections coming into those environments.
These days, were familiar with our mobile devices and being able to communicate from wherever we happen to be. We often call these cellphones. This goes back to the original configuration of our mobile networks where plots of land were separated into cells. We then placed antennas in very strategic points so that we could cover all of those different cells of land.
These days, a number of our mobile devices can even be used as a wireless router. We can enable a functionality called tethering. It turns on your mobile device as a central point for multiple devices to communicate over these cellular networks. Another device that works very similarly is a mobile hotspot. This is a device that looks like a normal wireless network to all of your devices, but it’s using the cellular network to communicate out to the internet.
Another popular type of network communication is one that uses line-of-sight. With line-of-sight, there’s usually a central antenna. It’s usually very high and at a central point. And everybody has individual antennas at their house or their business that are able to see and communicate directly to this central antenna. This is very common to see in very populous areas that need high-speed communication. And it’s easy to have a central antenna that everyone can communicate with.
There are also options for lower bandwidths, especially if you’re not able to get an exact line-of-sight to these types of networks. It’s very common to see this with something called WiMAX. This is Worldwide Interoperability for Microwave Access. It uses very high frequencies to communicate over this line-of-sight network to provide some very high-speed internet connectivity.
Category: CompTIA A+ 220-901