Faster Than a Speeding Electron!
As a follow-up to our discussion about streaming media, we're now going to take a brief look at high-speed internet access for home and small-business networks. Specifically, we'll compare cable and DSL connections.
If you're hoping for a definitive statement, "X is faster than Y", or even "X is better than Y", forget it. There are just so many variables, some of which change by the moment, that it's impossible to accurately predict which technology, cable or DSL, will be faster for YOU. Your next door neighbor may get different results. You may get different results depending on the time of day, the site you're visiting, or the type of data you're sending or receiving. Factor in price, customer service, reliability, and add-on services, and it quickly becomes pointless to discuss which is "better."
With the caveats out of the way let's get into some detail.
We said that it's impossible to determine whether cable or DSL will be faster under your circumstances, and that's true. It's also true that cable has the POTENTIAL to be faster. While a DSL connection could give you speeds up to 10 megabits per second (Mbps), and some proprietary systems can double that or more, cable can reach 30 Mbps. Theoretically. In actual practice you'd never reach that capacity with either option. A number of reasons...
If the cable or telephone wiring in your home is older or of poor quality, it may reduce your capacity.
In the case of cable, you're sharing your line to the Internet Service Provider (ISP) with all of your cable-using neighbors. (This used to be a security concern but has generally been corrected. Still, ask your cable company if they provide packet filtering or screening within the local area network.) If your neighbor's usage is heavy, your performance will decrease. DSL doesn't have this disadvantage; your connection to your ISP is dedicated just to you.
For DSL, as the distance from your home to the telephone company's switching center increases, the less bandwidth you'll have. That is, people who live closer to the central switch get a faster connection. (Sorry, but don't expect lower rates just because you live further away.) Cable doesn't suffer this limitation.
Your ISP may cap your bandwidth at a lower level to balance service for all customers, or to encourage you to pay more for a higher-end package.
Your ISP's gateway to the rest of the internet is also limited. If all of its customers start downloading large files at the same time, they'll all experience poor performance. In fact, the only way most ISP's can deliver even close to promised performance is if a large proportion of their customers are inactive at any given moment.
Traffic levels out on the internet will also affect your performance. During peak loads -- when there's some highly newsworthy event taking place, or when a virus is flooding the internet with junk email and denial-of-service attacks -- you'll notice a definite slowdown.
If the site you're trying to reach is busy or has a slow connection of its own, your access to it will be slow. The maximum speed you can reach to any one site is governed by the slowest link in the chain.
Another factor to keep in mind is that quoted speeds usually refer to downstream access, what you'll see when you're downloading files, browsing through web sites, or receiving email. Upstream access, when you're serving files from your own web server or FTP server, or sending email, is usually significantly slower. This is called "asymmetric." Symmetric access, with equal downstream and upstream speeds, typically costs more.
While we've used the words "bandwidth" and "speed" interchangeably, they're not really the same thing. Bandwidth is only one component of internet speed. We also have to factor in latency, how long it takes a bit of information to get from one point to another. Here's an illustration:
Suppose you've got a large cargo shipment to transport. You could send it via a single transport truck at 50 miles an hour, or in many small packages on motorcycles at 100 miles an hour. The transport truck provides greater bandwidth, but longer latency; while the motorcycle offers shorter latency but less bandwidth. If you need to send or receive a lot of data -- downloading large files for example -- you want greater bandwidth. If you need quicker response times -- for an online game perhaps -- you want lower latency. Ideally you'd like high bandwidth and low latency, but that's not always possible.
Besides just the speed of your connection, it's likely price is also a consideration. (If price is no object and you're willing to blow the bank, get an OC-3 connection; 155 Mbps for just a few thousand dollars a month.) Cable and DSL generally cost about the same, but you may be able to find a good deal by asking around. Since DSL works over telephone lines and those lines are often shared by several phone companies, you may be able to shop around for different DSL packages. With cable you may not have that option.
When making your decision, don't forget customer service (how easily can you get help if you need it?), uptime (how likely are you to lose your connection just when you need it most?), and add-on packages (like virus scanning, spam blocking, and firewall services.)
As time goes on we're likely to see more options for internet connectivity, such as service over power lines and wireless access. For now, if you need something faster than regular dial-up, either cable or DSL is a good choice for a small office or home network.
Regardless of which connection method you choose, even plain old dial-up, remember our discussion about security. Make sure you have a strong firewall and observe commonsense security precautions.