Digital Subscriber Line (DSL)

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Digital Subscriber Line (DSL)

Digital Subscriber Line (DSL)

DSL or xDSL, is a family of technologies that provide digital data transmission over the wires of a local telephone network. DSL originally stood for digital subscriber loop, although in recent years, manyhave adopted digital subscriber line as a more marketing-friendly term for the most popular version of consumer-ready DSL, ADSL. DSL uses high frequency, regular telephone uses low frequency.

Typically, the download speed of consumer DSL services ranges from 512 kilobits per second (kbit/s) to 24,000 kbit/s, depending on DSL technology, line conditions and service level implemented. Typically, upload speed is lower than download speed for Asymmetric Digital Subscriber Line (ADSL) and equal to download speed for Symmetric Digital Subscriber Line (SDSL).

Can I talk on the phone and surf the Internet at the same time?

Short Answer: Yes.
Long Answer: If your DSL is on a separate pair of wires, then your phone service is never affected in the least. If your DSL is on the same pair of wires as the telephone, you can still talk on the phone while you're connected to the internet. The filters that your phone company sends you will make sure that your telephone sounds as clear as usual.

Can I share the DSL connection between several computers?

Short Answer: Yes.
Long Answer: Depending on the type of modem that you have, you will either be able to just plug several network cables into the back of the modem (the Netopia 7000 series, for example, has a built-in 8-port ethernet hub), use an external ethernet hub or have to set up a proxy server. If you have a router (such as the Netopia 7000 series) then your router will typical perform network address translation and allocate fake IP addresses on the inside. You will typically be limited to about 255 computers connected this way, though there may be physical reasons why you can only connect fewer machines. If you have a bridge (such as the Efficient Networks SpeedStream 5000 series) then you have to set up a proxy server or some type of internet connection sharing software on one computer, and connect to the internet that way.

Are there any special requirements for the DSL modem?

Short Answer: No.
Long Answer: The DSL modem is a piece of equipment that you typically put somewhere out of the way. Under normal circumstances you should never have to touch it once your line is installed. This unit will always be on, even if your computer is off. All that is required to connect a DSL modem is a power plug and two wires (most modems ship with just one wire, so you will need to have an ethernet cable).

Is DSL reliable?

Short Answer: Depends.
Long Answer: DSL reliability is rather iffy. You can be lucky enough to install it and never have a problem again. Then again, you might be unlucky enough to spend time on the phone with technical support every week. My personal experience with the service (I have had DSL for over a year) has been mostly an uphill battle. The service is great when it works, but I have called support more times than I care to count. If internet connectivity is mission-critical, then I suggest you either have a dial-up account for backup (some DSL providers will give you dial-up access free of charge, but then if the problem is on their end, that may not help you in the least) or spend the extra money for a T1 line.

How fast is DSL?

Short Answer: Fast.
Long Answer: The fastest a regular dial-up modem can go is 56,000 bits/second (FYI: there are 8 bits in a byte). The slowest a DSL connection will usually go is 128,000 bits/second (you do the math). The fastest a DSL connection can go is about 6,000,000 bits/second. Typical home DSL connections will be 1,500,000 bits/second download and 384,000 bits/second upload speed or 608,000 bits/second download and 128,000 bits/second upload. How fast you can go depends on a) how many feet of wire there is between you and your phone company's office (Covad claims to offer 144,000 bits/second DSL service at almost 8 miles of wire) b) whether you choose ADSL or SDSL and c) how much you're willing to spend.

What is ADSL and SDSL?

Short answer: ADSL and SDSL differ in whether the speed is the same downloading and uploading.
Long answer: ADSL (asymmetrical digital subscriber line) has a higher download speed at the cost of a slower upload speed. ADSL is what is usually found in homes. SDSL (symmetrical digital subscriber line) has the same speed both ways. SDSL is usually found in small offices and home offices.

Is DSL safe?

Short answer: Yes.
Long Answer: In terms of safety from hackers, viruses and other problems DSL is almost as safe as a dial-up connection. I say almost, because the major difference is that DSL is always on. In a dial-up situation, a hacker typically doesn't have enough time to target your computer, but you're only connected for a few hours at a time and because your computer has a different IP address each time you dial your ISP. In a DSL situation, you are connected to the internet whenever your computer is on, whether you're actively browsing around or not. With DSL you will also typically be assigned an IP address that belongs to you and only you in the entire world. This makes your computer an easier target for hackers. You should always take security precautions when connecting to the internet, whether by dial-up or DSL.

How big is a DSL modem?

Short Answer: Roughly the size of a hard-cover book. (see pictures)
Long Answer: The Netopia 7000 series is about 9 wide by 8.5 deep by 2 tall. The Efficient Networks SpeedStream 5000 series is about 5 wide by 7 deep by 1.5 tall.

Is a DSL modem wall-mountable?

Short Answer: Depends.
Long Answer: The Netopia 7000 series is wall mountable. The SpeedStream 5000 series does not come wall mountable, but if you're handy, you could probably work something out.

Is a DSL modem rack-mountable?

Short Answer: No.
Long Answer: The modems in the Netopia 7000 series and the SpeedStream 5000 series are not rack-mountable. If you're aware of any DSL modems that are, please let me know.