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DSL & Cable Myths

This tech tip is more or less a continuation of last week's, where we discussed DSL vs. Cable for high-speed Internet access. This week we are going to discuss some of the common myths and misconceptions about these services.

1) Because it is shared, cable is not secure.

A common misconception is that because all of the cable subscribers in a neighborhood are on the same cable and do form a network of sorts, it is possible for your neighbors to browse your computer just as if you were all on the same LAN. The truth is, not only do many cable companies encrypt your traffic with unique subscriber keys, but upstream and downstream traffic is carried on different channels, and cable modems cannot monitor the upstream channels. Your neighbors have no more access to your computer that any hacker on the Internet would (and that's the subject of another tech tip or two).

2) Running a server on your cable connection won't affect the other subscribers.

This is technically true, but what matters is that servers typically create much more upstream traffic than normal web browsing. There is a limitation in the TCP/IP protocol itself that causes downstream traffic to slow down as much as 80% when the upstream channel gets saturated. This Internet phenomenon is called 'upstream saturation'. A few servers in your neighborhood may not matter but too many will create a crunch for everybody, and for this reason some cable companies prohibit servers on their connections.

3) You can only get cable Internet if you subscribe to cable TV.

It's actually up to the cable provider. Since the TV signal is already on the cable, it takes an extra step to block it out and there might be an extra charge for this 'service'.

4) DSL is easy to get and easy to install.

These are both 'iffy'. IF you live within 17,000 feet (about 3 miles) of a central office (by the length of the wire, not 'as the crow flies'), and IF your phone company offers DSL, and IF they aren't backlogged on installation, and IF there is a clean, quiet phone line with no crosstalk already coming into your home, then getting DSL is easy. That means at least 25% of us are just flat out of luck. As for installation, self-installation is cheaper and therefore more popular, but potential problems abound. For example, noise on the electrical line can get transferred to the phone line through the DSL modem, so if you have poor house wiring, dimmer switches on your lights etc., be prepared for some headaches getting your DSL to run without errors.

5) DSL can share your home phone line and won't interfere.

Yes, you can usually run DSL on the same line you use for regular telephone service, and even do voice and data at the same time, but you must put a special filter on each extension where you have a phone plugged in. These filters come with your DSL service.

6) The DSL upload capacity has no affect on the download.

Most residential DSL service has a maximum upstream capacity of 128Kbps. DSL is affected by upstream saturation just like cable, because this is a limitation of the TCP/IP protocol and not of the type of Internet access. This means that if your upload traffic approaches the limit, for instance because you are sending a very large file somewhere, your downstream speed will drop noticeably. Unlike cable, at least you only have to worry about your own traffic and are not affected by what other subscribers are doing. If you mostly just browse the web and send text e-mail, you won't need to concern yourself about it at all. However, if you frequently have large uploads for any reason, you might find out if your DSL provider has any upgrades with higher upstream capacity. And yes, it will cost you more per month.