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DSL vs. Cable Internet, What's the Difference?

This is something that I’ve been asked a lot recently. A lot of people don’t really understand what the differences between the two most common broadband internet types are. So as someone who has worked for not one, but two internet service providers I feel qualified to break it down for people.
If you’re looking for what you need to get connected at home, I’ve set up an Amazon store that has the products I recommend on it. Check it out and consider buying from there, the prices are almost always lower that what you’ll find at the retail stores.

What is DSL?

DSL is an acronym for Digital Subscriber Line. It’s basically a technology that sends data over a normal phone line (POTS line). Practically all DSL service in the US is actually “ADSL” which means Asynchronous Digital Subscriber Line. The only thing that means is that the download speed will be higher than the upload speed.
DSL is usually sold by one of two kinds of providers. The first type is the top-level phone company directly. By top-level I mean whoever actually owns the infrastructure that goes to your home. In the US this is usually a larger company like AT&T, or Verizon. There are also some smaller companies like Windstream that provide service directly to smaller towns.
The other DSL provider will be  a local, or semi-local re-seller  This is a smaller company that resells services for the top-level company. Basically they buy the loop (the physical wire or circuit that goes to your house or business) and sell it to you and then give voice and data over it themselves. Most of the time these smaller companies are a lot cheaper as they’re getting the loops from AT&T for a few dollars and then reselling to you for a profit. They’re also the most limited in what they can actually do. Typically their customer service is better to make up for speed deficiencies.
DSL, like all data connections, is limited by distance from the Central Office (DSLAM). You need to be within a mile (~2km) to get the best connection. After that first mile the guaranteed speeds will drop until you get about 19,000 feet (roughly 3.5 miles or ~5km) away. In my experience the smaller providers probably won’t offer you service at that distance.  This is where your re-seller companies fall short. Big companies like AT&T will put repeaters out so they can sell to more people at higher speeds. Smaller re-sellers typically can’t or more likely won’t do this so they are limited to a circle about three miles around the central office.
If you live in a small town you can safely assume the only central office is down town. Small cities will usually have multiple central offices so it might be difficult to find what kind of service might be available to you specifically. Unfortunately I don’t know of any tool available to the public to look this stuff up. Your internet service provider/phone company has access to these tools with the top-level company and they can tell you how far you are away.
Speeds vary from place to place. I’ve seen as high as 25Mbps download speed and as lows as .768Mbps download. For some reason download speeds with DSL are parcelled out in multiples of three until you hit the 20Mbps range, so you can expect to see 1.5 (half of 3), 3, 6, 12 and 15Mbps speeds advertised. Upload speeds are typically under a megabit as most home consumers don’t need upload speeds faster than that. If you do need faster upload speeds you can usually ask for them. Re-sellers are more likely to work out a deal with you than the bigger companies. Typically the lowest speed any company offers is 1.5Mbps download and .3Mbps upload (they’ll say 300Kbps to sound bigger). Of course the smaller the town the slower the speeds most of the time.
DSL service will require you to have a modem. Some companies will just give you a modem, most will just or rent you a modem at a discount with a contract. You can also provide your own and they’ll usually have a compatibility list on their website. Most Best Buy stores will carry modems compatible with your local service. I have an Amazon store with various equipment on it that is universally compatible. I HIGHLY recommend if you are considering AT&T that you get a modem from them as they will actually set it up for you. Be aware that if you provide your own modem, most DSL providers won’t give you any real technical support.
Note: I’ve seen some conflicting information about the distances I talk about above, some of it from sources on the internet, and from other people that have worked in the industry. I chose the numbers above because they were what I have been told most commonly over the phone, and what I had to tell customers when I worked at an ISP. Different technologies, geographical considerations, city size, line quality and other factors can drastically change what speeds you can get. The above distances are just a common rule of thumb, not an exact measurement for everywhere.
What is Cable Internet?
Cable internet service is a data connection that is provided through your cable service provider. The same coaxial line that your cable television comes in can be used to provide data (and voice services!) as well.
Most cable companies will provide some sort of internet service in addition to television. You’ll mostly hear cable internet referred to as “DOCSIS” (Data Over Cable Service Interface Specification). There are as of this writing three major versions of this. There’s DOCSIS 1, DOCSIS 2, and DOCSIS 3. There are a few minor versions but most home users don’t have to worry much about that.
This sort of internet service requires a few extra steps to set up but is usually more available to consumers. If you can get cable television, you can usually get cable internet. I am not sure what the limitations are as far as distance goes, but those limitations do exist. Some smaller towns may not have cable internet available even if the television service is. This is rare but I’ve seen it. Most people in those towns usually have satellite television/internet anyway because of how rural they are, at least in the United States.
It’s been my experience that cable providers can give you far higher speeds than DSL in the same area. The DOCSIS 3.1 standard should allow for 10Gbps download speeds. Even here in Amarillo, with a measly two hundred thousand population you can get 100Mbps download service to your house in many places if you are willing to pay for it. Smaller towns can still get 8-12Mbps service download speeds with cable if you are actually living inside the town.  Standard service seems to be in 20Mbps range for cities.
Like DSL, cable is delivered with asynchronous speeds. Your download speed will be higher than your upload speed. The trend is to give between 1 and 2 megabit upload speeds even if the download speed is far higher. Cable internet download speeds seem to be advertised in multiples of five for some reason. You’ll usually see 2.5, 5, 10, 20, 30 and 50Mbps speeds advertised.
A lot of cable companies will give you a modem if you ask. Usually they’ll rent them to you for $5 a month or so. If you are lucky they might just give it to you with a contract. As cable modems tend to burn out after two years or so, I recommend buying the modem yourself with home cable internet service. The biggest reason for home users is the leasing arrangement will cost you more over time, and you can usually get a compatible modem cheaper from Amazon or Best Buy than your cable company. If you have a business, lease the modem. Because they tend to burn out, the cable company will replace worn out leased modems and you get priority service (Sometimes you can just take the bad modem to the local office yourself and they’ll swap it out for you right there). If you as a business owner don’t want to lease the modem, buy two identical modems and keep one unopened as a spare.
Unlike DSL providers, it has been my experience that the cable companies will give you a bit more technical support if you provide your own modem. This is primarily because of how cable internet service works, you have to call them to activate the modem. If the modem is compatible with their service, they set it up for you. I’ve got an Amazon store set up that has modems compatible with most of the US cable providers.

So What’s the Real Difference?

The difference boils down to speed, who provides the service, and how big your city is.
Cable tends to be faster, cheaper and more available than DSL in many places. At least in my experience it tends to be a bit less reliable. You’ll have a few more outages per year than DSL. Usually cable companies tend to just say you can’t get service in an area and not telling you that your speeds will be lower if there’s a distance issue. One big disadvantage to cable is that there is usually one single provider that has a monopoly on the area so you can’t call somewhere else for a better quote.  Cable internet comes through your cable television provider.
DSL tends to be a bit more reliable, but it usually slower and a little more expensive in some areas (not always, sometimes it’s far cheaper than equal cable, but the top speeds aren’t as high). It also tends to be less available in smaller towns than cable. The other problem is that sometimes your next door neighbor can get a very fast speed, but you can’t.  One big advantage with DSL is that there are usually multiple competing companies in an area that can provide it. DSL comes through your telephone provider.
Either way you can get DSL without land line (POTS) phone service really cheap in most cities. If you get your DSL through a major company like AT&T there are some perks like free WiFi access at certain hotspots, which is awesome for people who travel a lot. If you get cable internet you usually get complimentary basic cable television with it, and you can usually also get your land line service as well for a discounted rate (I know people who have worked out their cable service in such a way that the internet is free and they pay a dollar for a land line).
There are advantages and disadvantages to both types and you should really call both kinds of providers and see what they have to offer before deciding. At the end of the day it really comes down to where you live and what you’re willing to pay.
I know I mentioned this at the beginning of the article and once in the middle, but I’m providing another link to the Home Internet Needs store on Amazon I set up so you don’t have to scroll looking for it.

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