Cable vs. DSL

Originally Written 03 May 2003

Recently there has been a huge push by digital subscriber line (DSL) providers to take a bigger chunk of the broadband market away from cable internet service providers. This has become even more apparent in recently thanks to Verizon and SBC (and I’m sure others will follow suit) dropping their prices dramatically. This is good for broadband subscribers and people looking into broadband because the cost of high speed Internet services is coming down. DSL and cable broadband both have their advantages and disadvantages but DSL seems to be the one lacking in quite a few areas and their marketing shows it.

DSL has many, many different types or versions. Asynchronous Digital Subscriber Lines (ADSL) are typically what most DSL providers offer to home users. These typically have a cap of 1.5 Mbps download speed and a provider specific upload speed that’s usually a significantly lower data rate. ADSL has a max speed of about 8 Mbps but this is rarely seen by home users (or even business users, for that matter). Symmetric Digital Subscriber Lines (SDSL) offer a greater upload speed (a max of about 2.3 Mbps) and an equal download speed (max of 2.3 Mbps). This is what is typically marketed to business customers as a replacement to the expensive dedicated leased lines, like T1s and fractional T1s offered by numerous companies. SDSL though is significantly more expensive because of their increased capability (which makes perfect sense). There are several other versions or types of DSL but ADSL and SDSL are your two typical flavors found just about everywhere. As the case with any DSL line, it’s a dedicated circuit between your location (home, building, apartment, etc.) and the Telco. There are also limits to the distance a DSL circuit can be run. So even if DSL is available in your area, your specific phone line might not be able to get it. DSL also requires some trickery in terms of wiring jacks with filters so that your phone system still works as it should when you’re also connecting to a DSL service. Cable requires a filter as well but one filter (or the removal of a filter depending on your cable company) works for every jack in your home.

Cable Internet services are limited only by the providers’ use of frequencies. The technology is pretty the same across the board which eliminates the version/type issue that DSL has. Cable providers that offer high speed Internet access typically use one channel (6 MHz) for download streams and a much smaller channel for upload streams. There is quite a bit of technology involved in getting signals converted to and from the coax/fiber cable network to the Internet but it’s a rather efficient process in comparison to DSL and offers much more than just high speed Internet access (HDTV, voice, digital cable, etc.). We all know that both cable and DSL are “always on” technologies. The one downside to cable is that you share bandwidth with other people. Cable providers use a cable modem termination system that essentially takes the Internet and puts it on your coax. These systems are fed a very high speed (typically ATM) Internet connection (for ideas of the speed of ATM see our Bandwidth Reference). This termination system is where all the users of cable Internet in your area get their Internet access from. In a sense it distributes data from one source to numerous other sorts, much like a hub in a LAN. This is cable Internet’s one major flaw but is typically overcome by assessing the bandwidth needs of specific areas and increasing or decreasing the feed as necessary. This is one of the reasons cable providers rarely mention guaranteed speeds or latency.

Cable versus DSL is a tough one. For a long time DSL was a more reliable option because of the guaranteed data rates. But there were limiting factors like distance from your local Telco and price. Cable clearly became a better option even though it was a shared technology (which helped drive the price down) because of its flexibility in delivering Internet access to entire areas in one fail swoop. Cable providers have also adhered to standards (Data Over Cable Service Interface Specification or DOCSIS) thus simplifying development of networks unlike DSL’s flavor craze, which runs off unknowing users in my opinion. Cable for the moment is significantly cheaper for what you get in terms of bandwidth even though that bandwidth is dependent upon so many factors (population, time of day, etc.). Based on price alone cable seems to be a better overall option if both cable and DSL are available in your area. I’m partial to cable myself because I’ve never had a real problem with it (and I did go through the @Home bankruptcy). I’ve never once met a happy DSL customer.

DSL providers market things such as “dedicated” which is true in the sense that from the Telco to you wall jack it is a dedicated circuit. But, from the Telco to the Internet you still share the bandwidth with everyone else connecting to that Telco (which could easily be more than “your neighborhood”). At least cable providers acknowledge the fact that their users share bandwidth and build their networks so that each user has the best possible experience. Verizon has actually gone as far as saying (on their web site) that you can’t, “Use the same phone line for phone or fax and Internet” with cable. This is a very moot point because cable Internet doesn’t use a phone line. DSL providers typically require a contract (12 months or more) to be signed for any service. Cable providers typically don’t require this because no matter what if cable Internet is available in your area your house is getting it’s just being filtered out. When setting up DSL for your phone line typically, someone actually has to do physical labor at the Telco to provide you with service so a contract is to be expected so that the labor charged to your provider can be reimbursed somehow. There are numerous other things to look at when you’re making a decision about broadband and typically it is area specific but if both DSL and cable Internet access are available to you my advice is to go with cable.