Review: Linux and DSL

by Andy Dubman

I received a mailer from my phone carrier, US West (I live in Minneapolis) advertising the new DSL service they were offering. I thought it would cost a fortune based on the speed they were offering. After calling, I was surprised to find out that it was only slightly more than my dial-up 33.6k line. I was informed that I would have to wait for about 3 months until the service was available in my area. I continued to use my painfully slow 33.6 in the meantime.

My telco was offering a promo on the service...A free "modem" (actually a small Cisco router) but the installation charge was $100.00. I know a little about networks, so I asked if I could install it myself. I told them I was using Win '95, which I was at the time.  They agreed and I saved the $100.00.  They sent me a complete "do-it-yourself" kit with very clear instructions, and a copy of Netscape for Windows for DSL (no different than the regular dial-up version). Do not be afraid. It works great with Linux and is very easy to set up.

DSL stands for "Digital Subscriber Line". It uses a new technology called "voice over IP" which means that normal telephone traffic (voice or fax) and network information (TCP/IP) travel over your existing copper phone lines with out interfering with each other. DSL requires a network. This network can consist of your computer with a network interface card (NIC), the router and a cable. If you have more than one computer, you need to use a hub and normal cat 5 data cable. This requires some additional work that I will not go into here. Since Linux (and most other modern operating systems) support TCP/IP, it's very easy to set up, even to someone who has never used either Linux or DSL before. It took me about 20 minutes to set it up, and it worked the first time with no complications. In fact, it's easier to set it up with Linux than Windows.

When I built my Linux box (Intel Pentium 233MMX/64MB SDRAM/5GB hard drive) I installed an ethernet card.  The one I used was an Addtron 380. It uses a Digital Equipment 21440 chip which used the "tulip driver". I am running Red Hat 5.2, and as of last November when I built it and installed Red Hat, I had never touched or seen Red Hat in action before. It has been a great experience, I'm liking it and have since converted to Red Hat as my primary desktop system. Control-Escape has helped me overcome the learning curve, and I appreciate that. Linux has been rock-stable and NEVER crashes.

I still had my old Windows95 box at the time I set up DSL, and since setting up my router required that I communicate with it via telnet, and I did not know how to do that with Linux at the time, I completed that task with the Windows box. [Ed: just type "telnet <destination_address>" at a Linux command prompt.] It was very easy and only took a few minutes, using the serial cable supplied with the router. The router's operating system user interface looks exactly like Linux's command line interface. Makes you wonder what it runs on...

The documentation with my router (Cisco 675) had very clear instructions on the three steps necessary to configure and test the installation:

1) log in
2) enable bridge mode (by typing one command)
3) test the line for noise and speed (two commands)

When I plugged in the router as the instructions told me and booted up Red Hat, the lights went on, the messages on my screen indicated the NIC was picked up by Red Hat, and it was using DHCP, which dynamically assigns the NIC it's IP address. At that point I knew it would work. I launched X, opened Netscape and instantly my home page came up. I thought it may have been a cached copy it was so fast, so I typed in a URL and within about 2.5 seconds, the page loaded. BLAZING FAST!

DSL has been consistently very fast ever since day one. My cost from USWest is $40.00/month plus my monthly ISP fee of 19.95. I was able to discontinue my second phone line which saved $26.00/month.

I connect to the Internet consistently at 256k. If you are not familiar with speeds, that's almost 9 times as fast as a 28.8 modem and 4.5 times as fast as a 56k modem (assuming a full-speed connection, which almost never happens with modems). It's twice as fast as ISDN and less money. The router I was furnished uses DHCP to supply IP addresses to the computers on its network, and it acts as a rudimentary firewall. [Ed: For techies and security gurus, it uses port address translation. For details see Cisco's Data Sheet.] It's pretty hard to hack in to.

The connection is always on, which means there is no dial up or delay of any kind. Open Netscape, Pine or whatever browser you wish to use, and you're on the Internet. You can talk on the phone or send a fax at the same time with no interference.

A lot of people talk about cable modems these days. I don't work for a telephone company or any other DSL partial entity. The following is my opinion after talking to the network engineers I interface with at work.

Although cable is fast, this technology uses shared bandwidth. What that means is that during the middle of the day when you are the only person in the neighborhood who's home and you're on the net, your speed is very good. When all the kids get home from school and log on, the speed bogs down. After work when all your neighbors go on, it gets slower. If your neighbor is a sysadmin and uses LANanalyzer, he can see your computer and look at your information. With DSL, he would have to be at your telco's switch to see your computer. It's direct connection to the telco.

To see if you can get DSL, call your phone company. It's an inexpensive way to get a fast connection, and it will work with any computer system that supports TCP/IP (Linux, Solaris, HPUX, MAC, WIN...)

And remember...Safe Surfing is Happy Surfing!

Andy

© Copyright 1999 by Andy Dubman. Used by permission.