Internet Connection Types – CompTIA A+ 220-801: 2.7

| December 2, 2012


There are many different methods available today to provide us with access to the Internet. In this video, you’ll learn some of the most common methods for connecting to the World Wide Web.

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If you’ve been tasked with connecting your organization to the Internet, then you’ll find you a lot of options available for network connectivity. In some organizations, you’ll find you’re using multiple methods to be able to connect to the Internet. In this video, we’ll step through many of those and give you an idea of what options might be available to you.

A type of Internet connection that’s very common to see in homes and these days also in businesses is a cable mode. This is where we are putting the data on the cable that traditionally has provided us with a video signal. We are now using it for data, as well. There’s a standard associated with this. It’s called DOCSIS. That stands for Data Over Cable Service Interface Specification. And that’s the standard set of protocols and methods that’s used by that cable modem that takes data off of that cable line and provides it to you over an Ethernet connection.

One great advantage of data over this cable is because we have a cable in the ground, we can give you very, very reliable, high speeds. You’ll often find options for cable modems that run about four megabits per second all the way up to 100 megabits per second. And newer specifications are even looking to push that even further.

There are multiple services you can get over this, as well. The cable providers have realized that once you have data you can do an amazing amount of things. You can not only provide traditional Internet connectivity, but you can also provide voice services. So they can provide you a telephone line and simply use voice over IP using that data path.

Another common type of Internet connectivity is called DSL. That stands for Digital Subscriber Line. The type of DSL that you commonly see is actually called ADSL, with the A at the beginning. That A stands for asymmetric. That’s because the download speeds that you receive over DSL are different than the speeds available for upload. Those speeds are therefore asymmetric.

This uses the phone lines that you already have in your house. So it’s very common to see this implemented because you don’t have to run new cables. You don’t have to run new connections inside of your home. You simply plug into a telephone jack that you might already have in the wall.

One significant disadvantage of DSL is the distance limitations that are in place. You have to be about 10,000 feet or less away from the central office where all of this data comes from. Otherwise, the signals aren’t able to make it all the way to your home. And the farther away that you are, the slower the connectivity that you’re going to have. Normally, we would see the best possible scenario for DSL be somewhere around 24 megabits per second on the downstream side as you’re receiving data. And the upload side is usually somewhere around three and a half megabits per second. Higher speeds are difficult to achieve through ADSL because of the limitations in the cabling and the type of signaling going over those cables.

A standard you may sometimes see referenced is symmetric DSL or SDSL. There was never a standard created for that. The technical problems simply didn’t allow a standardized method of receiving and sending at exactly the same speed. But there have been improvements to the DSL standard. One is VDSL, which is Very High Bitrate DSL. And you can see the bitrates. They are very comparable to cable modems. You’re getting anywhere from four megabits per second all the way through 100 megabits per second.

Although a lot of the talk that we have today revolves around high-speed Internet access and broadband connectivity, there’s still a number of people using modems to be able to communicate to the Internet. Modems are simply using our standard phone lines and connecting to them just like we would dial a phone number inside of our home. This phone line connection, though, limits the frequency response we can get. And therefore, you get some pretty slow throughputs when you compare it to some of the more modern connectivity.

For example, your modem is probably going to connect at a speed of about 56 kilobits per second. That’s not 56 megabits per second. That’s 56 kilobits per second. And if you can compress some of the data on that connection, you can sometimes get some optimal speeds of about 320 kilobits per second, but still well short of even getting close to a megabit per second. The lines and the connectivity and the technology behind dial-up connections simply don’t support those types of speeds.

Because of the technology behind this and the slow speeds, it becomes difficult to scale this very large. We know that when we’re going to dial up a connection that we’re going to need a phone line on both sides. And even then, we’re going to have to transfer data over a long period of time just to get that data between point A and point B. It’s even getting difficult to find a modem manufacturer these days. There’s a declining number of manufacturers who are actively creating modems.

But if you’re in an area that doesn’t have high-speed Internet access– there’s no wireless type of connectivity– this is one of the only ways to connect one of those very, very remote sites back to a central place, is over a common telephone line.

A relatively new high-speed connectivity for Internet access is taking fiber optics and bringing it right to your home. This gives you a lot of flexibility with connectivity because you can do everything over the fiber. There’s so much bandwidth available you can run video over that connection, you can have your telephone lines over that connection, and of course you can have your Internet connectivity over that connection, as well.

And these providers of this connectivity are also providing you things like storage in the cloud. You’re going to have up to a terabyte of data that’s sitting in the cloud. And because you’re over such a high-speed connection, it’s as if you have a local hard drive, except now it’s located somewhere else outside of your home. Some of the DVRs on here are two terabyte DVRs. You can effectively record for days and days and days and be able to rewind back and watch any type of program you’d like.

Of course, you don’t have to use earthbound methods to be able to communicate out and get Internet access. You can also use non-terrestrial methods like a satellite connection. This is communicating from your ground station, from your computer, directly up to a satellite and then back again. So we’re leaving the planet Earth to be able to make this Internet connection.

And we can get some pretty good throughputs on this connectivity, as well. If you were buying this for the home, you can have common upload speeds at about one megabits and download speeds at about five megabits per second. So this is great for remote sites or sites that you can’t get connectivity to.

But obviously, because of the technology involved there are some additional costs associated with this. You normally have to buy this equipment. They’re also a high cost to be able to have the connectivity there at all. It’s not quite as cost effective as having a cable modem or a DSL line. But if you don’t have any other type of connectivity, this is a very good choice.

A significant disadvantage, however, is that the latencies are pretty long. You have to go all the way up into space and back down to Earth again. And then to complete the loop it has to go back to the satellite and then back to you again. So your latencies are somewhere around 250 milliseconds up and 250 milliseconds down. This is a lifetime if you’re thinking about network connectivity. And if you’re trying to do real-time type functions over this connection, you’ll find that the latency may not allow you to do that.

We also have high frequencies that are in use here. We’re using about the two gigahertz range to be able to communicate up to that satellite and back. And it suffers through problems if anything gets in the way. This is line-of-sight, so you have to make sure there are no trees around. And then if it does start to rain, you may suffer from what they call rain fade, which means your connectivity either decreases or disappears completely.

A legacy connectivity technology that you may still find in use is ISDN. SPN This stands for Integrated Services Digital Network. There are two types of ISDN connections that you’ll find. For someone who’s in a home or small business, you’ll commonly see what is called an ISDN Basic Rate Interface. We commonly call that a BRI interface.

You may see this also referred to as a 2B+D. The B stands for what we call the bearer channels. This is the channels where your data is going over these connections. And because there are two B, there are two 64 kilobit per second channels giving you a total of 128 kilobits per second. I mentioned legacy, and obviously the speeds here certainly point to an older technology.

The D associated with that 2B+D is a signaling channel. So as you’re sending data back and forth, there is a completely separate data channel that’s used to configure, set up the calls, tear down the calls, and handle the management of the connectivity.

If you are in a larger environment, you might be using ISDN PRI. That stands for Primary Rate Interface. In the US, it’s delivered over T1. Elsewhere in the world, like Europe, you may see this delivered in an E1 configuration. A T1 is 23 bearer channels and a data channel. If it’s an E1 it’s 30 bearer channels and a D channel. Plus there’s an extra alarm channel associated with that.

We usually see this in very large environments. If someone has a PBX with multiple phone lines coming in, it’s not uncommon to bring a single ISDN PRI connection in because there are 23 separate phone lines, effectively, connecting into your PBX. And that way you can have a lot of people calling you at one time. Obviously, for data centers for medium- to large-sized businesses, this may be a good way to connect up your phone lines.

In our society today, we love our always-on Internet. Wherever we go, we need to have that Internet access. And we have the same thing through our cellular networks, as well. The same technology we’re using for our mobile phones can also be used to send data, as well.

And that’s because we have these antennas that we put all over the countryside. And those are connecting up into what people have called cells. And we are having certain frequencies being handled by different antennas. And as you travel through the countryside, it hands you off from one antenna to the other.

We’ve seen this with legacy 2G networks using something called GSM, which is the Global System for Mobile Communications, and CDMA, which is the Code Division Multiple Access protocols. What we’ve found with these older 2G technologies is that the data support wasn’t very good. We tried to add on the data piece after the fact, and we have some limitations associated with that. So if you want to have some faster throughputs and faster speeds, you probably want to use a newer method of communicating.

That’s why our mobile companies have upgraded to things like LTE and HSPA+. This is something from the Third Generation Partnership Project. You’ll see this abbreviated as the 3GPP. All of the telecommunication companies got together to find a common way to send data over these connections.

A common one is LTE. That stands for Long Term Evolution. It’s based on the GSM or the EDGE-based networks. And we have some very good throughputs. Your theoretical maximums on these are somewhere around 300 megabits per second. The upload theoretical maximum is somewhere around 75 megabits per second.

We’ll also see HSPA+ from some manufacturers, as well. That’s based on the CDMA type of technologies. And you’ll see download rates somewhere around 84 megabits per second and upload of 22 as a theoretical maximum.

But generally, when you’re using either LTE or HSPA+, you generally get much slower throughput than that. But still very, very high speeds for someone who’s wandering around in a mobile environment and needing to have that Internet access.

Another type of Internet access that we see put it in regional areas around the world is something called WiMAX. That stands for Worldwide Interoperability for Microwave Access. And this is effectively a very large scale wireless network. We can have up to a 30-mile radius. So people have called this Wi-Fi on steroids. You can obviously go anywhere in that radius and have that high-speed Internet connectivity.

If this is a line of sight where you’re able to see that antenna and get direct access, it’s using a standard called the IEEE 802.16. And the throughputs are pretty good– 37 megabits download and 17 megabits upload.

Another update to WiMAX is one called Mobile WiMAX. This is one that is the IEEE 802.16e. And it is one that, if you have a fixed station, increases those speeds up to a gigabit per second download. And if you’re in a mobile device, you can actually get about 100 megabits of throughput on those devices.

So some great capabilities. Obviously, you need the infrastructure in place to be able to handle that connectivity over a large area. But if it’s in place, that might be a good Internet option for you.

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Category: CompTIA A+ 220-801

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