DSL: also known as darn speedy link
DSL: also known as darn speedy link
A dial-up modem can occasionally hit 53 Kbps; a DSL connection can reach 10 times that speed
By Michael Cheek
What does the acronym DSL stand for?
A. Digital subscriber line
B. Darn speedy link
C. Dependability sometimes low
D. Dangerous snake lair
E. All of the above
If you chose E, you're right. OK, maybe D doesn't apply unless the Category 5 cables get tangled around your feet.
After about four weeks of DSL use'sometimes struggling with it, often enjoying it'I've seen a glimpse of the broadband future. DSL got its start with home users impatient for faster connections, but it's now infiltrating the office, and with good reason.
At the GCN Lab, we pay $500 a month for a fractional T1 line with about the same bandwidth as my DSL home connection, which costs less than $50.
DSL business accounts run only $100 or a little more per month. Unlike frame relay, Integrated Services Digital Network or other standard business connections, DSL requires no special wiring into the office. Its traffic travels over the same copper lines used by analog telephones'a great advantage.Two for one
Instead of adding phone lines, you can have data and voice share the copper. Offices with private branch exchanges cannot put DSL onto that copper, but chances are good that they already have one or more dedicated analog phone lines for faxing or for emergencies when the PBX goes down. DSL can share one of those lines.
If the power goes out, the analog phone line still works for voice traffic, although DSL won't. The thing to remember is that DSL does not interfere with the voice connection at all.
DSL isn't reliable enough yet for critical connections. But for a field office or small workgroup location, it's an economical broadband option.
DSL has become the catchall term for several services. This article will focus on asynchronous DSL. In the mid-Atlantic and Northeast, Bell Atlantic Corp. (soon to be renamed Verizon Corp.) is the leading DSL provider. Even if you order DSL from another company, Bell Atlantic probably provides the service.
The situation is similar in other regions because the local Bell operating companies control the copper telephone lines pretty much everywhere.
DSL's digital signal piggybacks on the analog voice signals. A DSL access multiplexer, known as a DSLAM, must be located close to wherever DSL subscribers link up. Depending on the type of connection, a DSLAM has to be within about 20,000 feet.
Because it requires no special wiring, DSL installation is becoming a do-it-yourself job. Bell Atlantic sent me an installation kit with a modem and several filters to split the digital signals from the analog'data from voice.
It was surprisingly simple to get a single computer onto the Internet. I plugged in the DSL modem to wall current and to a phone line. I connected the computer's standard network interface card to the modem, installed a little software and watched all the lights turn green.
Bell Atlantic's DSL service uses Point-to-Point Protocol over Ethernet. PPPoE acts a lot like a dial-up connection without the dialing delay. Connection is almost immediate.
Bell Atlantic and other providers are rapidly adopting PPPoE because the connection at the telco's end acts just like dial-up, too.
Bell Atlantic cautioned that DSL wouldn't work until after 6 p.m. on the first day of service, and technical support would close down at 8 p.m. But my connection was working by 6:30 p.m.
Next I had to set up the account, which was where I hit a glitch. Bell Atlantic's software included a special version of the Netscape Navigator browser to assist in account setup. But the registration server appeared to be down. So I called tech support and waited.
I ended up establishing the account the old-fashioned way, over the phone talking to an operator. When that was done, I dialed in and connected just fine.
Using a ping command in an MS-DOS shell session on the computer, I confirmed that it was connected to the Internet. I also discovered that the connection was very, very slow. I told the Bell Atlantic technician, who instructed me to hang up and send an e-mail message about it.
For that, I had to use my old dial-up account. It seemed a little weird that I needed to send e-mail when I was speaking with a representative on the phone.
Although I got confirmations via e-mail that Bell Atlantic was working on it, I never received notice that the problem had been fixed. But two days later, my PC was screaming on the Internet. When I say screaming, I mean the connection reached 500 Kbps.
Connecting by dial-up modem, I occasionally get 53 Kbps. So my DSL connection was almost 10 times faster than the fastest analog modem.Down is up
The Linksys router was very easy to set up'from the DSL modem to the router to the hub'to manage DHCP tasks for a network. It also insulated the network from attacks.
Most small-business DSL connections, like mine, are asymmetric'the download speeds are much faster than the upload speeds. Small-office and home DSL users can upload at about 90 Kbps and download up to 640 Kbps. For that reason, ADSL is not ideal for hosting a Web site, because the Web server needs to send out data as fast as it comes in.
The connection speed varied during the day. From 9 a.m. until 10:30, I'd see 200 Kbps to 300 Kbps. Then it would rise to between 350 Kbps and 400 Kbps. Around 5 p.m., the speed dropped to about 200 Kbps, probably because other DSL customers got home and started surfing. As the evening wore on, the speed climbed back to almost 500 Kbps.
How do I know? A Web site and an application told me.
Microsoft Corp. offers the Speed Test at www.computingcentral.com/topics/bandwidth
. After you wait a few moments, the Web site tests the connection feed. The first Web page has a large data file in the header. When your computer requests that page, the time is noted. Then code at the end of the large file requests a second page. When your computer requests that second page, the time is noted and the transfer speed calculated.
Another handy tool for determining speed and even more data about your connection is Net.Medic 1.2.2 from Lucent Technologies NetworkCare. This free software'available for download from www.ins.com/software/medic
'can analyze any connection and lets you know when the Internet is clogged.
The Net.Medic dashboard shows statistics about downstream and upstream rates. It tells how many hops the packets are making to and from servers. It can also tell when a server is failing to respond to a data request.
It also reports the general health of your PC, such as the load on the CPU. An overloaded CPU can cause surfing delays.Free floating
You can leave the individual panes of information in Net.Medic's dashboard or set them free to float by themselves. A few can be embedded as a tool bar in the Web browser.
Net.Medic tracks connection performance over time and provides quick statistical reports. If problems arise, it can also make suggestions for fixes. It even has an information pane for a modem'an analog modem, not the DSL kind. Perhaps future versions will support broadband products.
The 1M Net.Medic download takes up less than 2M when installed.
I found the Microsoft Computing Central Web site and Net.Medic came within about 15 Kbps of each other in their speed ratings.
So far, I had a terrific connection for one computer, but I have more than one computer at home'three, in fact, linked in a small network. The next step was to extend broadband Internet to the other PCs.
Net.Medic detects roadblocks anywhere from a local PC to the Internet itself.
My inclination was to use Microsoft Windows 98 Second Edition's Internet Connection Sharing. It turned out to be a bad choice.
First, I had to upgrade each system to Win98SE, which was tricky. On one system, when I selected Internet Connection Sharing, it never installed or showed up as an option under Windows Setup'the tab under the Add/Remove Programs icon in the Control Panel.
A second system upgraded more smoothly and showed ICS. To share the DSL connection, that PC needed two network cards: one for the DSL to come in, another to send the Internet traffic out to the network.
When ICS is working correctly, Win98 acts like a router. Only one computer needs to have it installed, and a wizard walks you through the installation.
After I designated each network card correctly, the wizard generated a floppy disk with a small application to set up all the other computers with the correct settings.
It didn't work.
Over several hours, I set and reset both PCs' network settings, which are not easy tasks. In the end, the PCs could see each other on the network and trade data, but ICS never worked.
I discovered the problem relates to PPPoE. Microsoft's support Web site refers users to another site that suggests a series of manual changes to the Windows Registry. Here's just the first step in changing the relevant entries:
'Add or change the MTU value for the NetTrans registry key for the network adapter (or the HSE service adapter for the gateway computer) and values for the MSTCP registry key and delete the Microsoft ICS InternetMTU key, if present.'Say what?
Perhaps I could have deciphered the instructions eventually, but I found an easier solution, recommended by another user who has a cable modem.
Linksys Group's Instant Broadband EtherFast Cable/DSL Router has a long name but short instructions. Linksys sells two versions: The BEFSR11 has one port to connect to an existing network, and the BEFSR41 has four ports, also acting as a 10/100-Mbps switch.
I already had a 100-Mbps hub with four ports, so I got the single-port version.
Why spring for 100-Mbps Fast Ethernet equipment when a 640-Kbps DSL connection can't begin to fill up the pipe? Standard 10-Mbps Ethernet would have sufficed, but I was thinking ahead. Internet connections will continue to get faster. Users weren't satisfied with 28.8 Kbps, 33.6 Kbps or 56 Kbps, and it probably won't be long until 640 Kbps seems too slow.Easy connection
The price difference between 10- and 100-Mbps hubs and network cards is minimal. Moreover, standard Ethernet devices are disappearing.
Linksys' router connected right up with ease'from the DSL modem into the router and out of the router to the hub. The router acts as a Dynamic Host Configuration Protocol server, assigning addresses to all PCs on the network.
But first I had to uninstall ICS and all the Bell Atlantic software on the primary system. Then I enabled DHCP and rebooted. The router, by default, set its IP address as 192.168.1.1. That address is not found anywhere on the Internet; it's meant for private networks and so is generally safe.
Because the router is exposed on the Internet, however, I recommend changing its default password. It's unlikely but conceivable that someone could hack into the router. I could not 'reach' it from an outside connection.
Furthermore, the router acts like a firewall between your individual systems and the Internet. It would be extremely difficult for a hacker to get into your network. But don't neglect installing virus protection software to guard against e-mail attacks.
Troubleshooting utility for Internet connection problems
Lucent Technologies NetworkCare; Sunnyvale, Calif.; tel. 888-767-2988
+ Detects Internet communication status and speed
' Doesn't recognize DSL modem hardware
Win9x or NT 4.0, Pentium II or faster processor, 36M of RAM, 2M of free storage, Explorer or Navigator 4.0 or later browser, active TCP/IP stack
Instant Broadband EtherFast Cable/DSL Router
Linksys Group; Irvine, Calif.; tel. 949-261-1288
Price: $104 for router; $160 for four-port switch or router
+Very easy management via Web browser
+Some firewall protection
'No detailed control of communication ports
Linksys did a terrific job of simplifying router management through a Web interface. Moreover, the PPPoE setup was easy. I typed in a user name and password, selected Connect, and my network was on the Internet.
Any PC can use up to 65,535 communication ports. For example, Port 21 is for File Transfer Protocol traffic, and Port 80 is for Hypertext Transfer Protocol. The Linksys router worked well on such common access protocols.
But some applications use more complex port arrangements. A videoconferencing program I installed to chat with a friend in Germany uses the following ports: 2,000 to 2,033, 2,050, 2,051, 2,069, 2,084, 2,095, and 3,010 to 3,030.
The Linksys router was too effective as a firewall, blocking some of those ports. Under the more advanced settings, the router offered the option to forward certain port connections to a particular PC on the network. This is handy if, for example, you're running an FTP server on one system. The forward feature works on only 10 ports, however, and I needed 60 ports.
Also under advanced settings, Linksys provided a so-called demilitarized zone setting. If you insert a PC's IP address here and enable it, the PC is no longer protected by the firewall.
This can be handy, but when I want to conference with my friend in Germany, I must leave my system vulnerable to hacker attacks. Some of the personal firewalls reviewed recently [GCN, April 3, Page 33
] could help here.
Only one system on a network can be in the DMZ at a time. That's protection, but it limits access for some uses.
I tend to leave the DSL connection always on. After the link has not been accessed for a while, the connection can go away. When it doesn't work, I log on to the router, disconnect and then connect again. Sometimes it won't connect immediately, but a second attempt works and bandwidth returns.
This is basically the same operation as rebooting a PC; the reinitialization clears whatever is clogging the line.
The Linksys router makes accessing the Internet easy and controllable over a DSL connection. Although my DSL connection still fluctuates in speed and has gone down a time or two during thunderstorms, I've found it well worth the effort to install. I once paid $24 a month for a 56-Kbps connection at home.
Now I'm running almost 10 times faster for about twice as much money. It's worth it for any field office that needs broadband speed.
|Glossary of DSL terms|
|Asymmetric DSL: Provides a fast downstream but a slower upstream connection. Most basic ADSL connections upload at 90 Kbps and download at up to 640 Kbps. Faster versions can reach up to 6.1 Mbps with special wiring. Standard ADSL shares analog phone lines via a splitter to divide the voice from the data.|
ADSL Lite: Transmits up to 1.5 Mbps with a DSLAM as far away as three miles. ADSL Lite uses filters instead of a splitter to divide voice from data. Most home and small-business connections today have ADSL Lite.
CDSL: Consumer DSL, a version of ADSL proposed by Rockwell International Corp., supports 1 Mbps downstream and 128 Kbps upstream with a DSLAM within 18,000 feet.
DSL Lite: Same as ADSL Lite.
DSLAM: DSL access multiplexer that blends data signals with voice.
G.Lite: Same as ADSL Lite.
HDSL: High-bit-rate DSL delivers the T1 rate of 1.5 Mbps via two twisted copper pairs. A second version, HDSL2, is expected to carry that rate on a single twisted pair. HDSL cannot share analog phone lines, and repeaters are necessary every 6,000 feet.
IDSL: Integrated Services Digital Network DSL is symmetric and delivers 144 Kbps, which is 16 Kbps more than standard ISDN. IDSL cannot share analog phone lines.
RADSL: Rate-adaptive DSL varies its speed based on signal quality, reaching up to 640 Kbps. Some ADSL connections are in fact RADSL. RADSL can share analog phone lines.
SDSL: Symmetric DSL uses a single twisted pair to deliver the same rates upstream or downstream, from 144 Kbps to 1.5 Mbps. SDSL cannot share analog phone lines. SDSL sometimes means HDSL2.
UDSL: Universal DSL, same as ADSL Lite.
VDSL: Very-high-bit-rate DSL goes over fiber cable in areas with numerous connections. Often it's referred to as FTTN, or fiber to the neighborhood. Depending on the distance between repeaters, VDSL is able to transmit from 12.9 Mbps to 51.8 Mbps.
DSL: Generic DSL applies to all the terms listed above.