The following information concerns the application of DSL services from Netpath, Inc. It does not necessarily equal the DSL implementation of any other service, and hence there may be distinct differences between this information and that published elsewhere. A handy FAQ is published at http://www.everythingdsl.com/faq.html and may answer questions which are not discussed here. There is also a good article in the August 2000 edition of PC World.

What is DSL?

DSL is an acronym for Digital Subscriber Line. This is a generic term that encompasses different types of lines. Here are some flavors of DSL:

I-	DSL is ISDN DSL which supplies 144K.
A-	DSL is Asymmetrical DSL which supplies faster download speeds than upload.
S-	DSL is Symmetrical DSL which splits the channel into two equal halves.

See also http://www.everythingdsl.com/whatisdsl.html for more information.

What DSL does Netpath Offer?

Netpath offers currently ADSL from BellSouth which is 384-512kbps download speed, bursts up to 1.5mbps for most websites & small files. 256kpbs upload speed, but 192kpbs is more realistic.

* Speed is not guaranteed in any way: your speed will be affected by many factors, including the speed of the Internet itself, and of the sites you visit. There are other business class services that optionally may be offered.

How Does ADSL Work?

An ADSL generally depends on there being a solid copper connection between your facility and the phone company's DSLAM (a special unit that provisions DSL services) within a specified distance (generally about 3.5 miles). This means that there can't be anything on the line to disturb the signal. Things that can cause trouble are:

Fiber-optic runs	many fiber-to-the-curb neighborhoods are not DSL capable at this time.
Bridge Taps	test wires attached to the normal copper pair. These wires are connected only at one end and are unconnected at the other end. Hence they behave like radio antennas capturing high-frequency signals and rebroadcasting them on the line and causing interference.
Load Coils	reduces hum and static in long runs of copper line. These devices compensate for the wire's capacitance and block out all non-essential frequencies for voice communication (anything greater than 4KHz).
Shorts	moisture can induce small shorts in copper lines which create attenuation (suppression) of high-frequency signals used by DSL.

The telephone company will attempt to sidestep these problems by not qualifying any lines suspected to have them. In some cases, there is solid documentation of the existence of these problems, but in others, Ma Bell is not sure what actually exists on a line! Remember, some of these copper lines have existed since the early part of the 1900's.
ADSL runs on the same line as a voice circuit. Since voice uses frequencies between 0 and 4KHz (4000 cycles per second), any frequency above this can be used to multiplex (multiplexing is adding more than one signal together) a different signal. ADSL uses frequencies between 10KHz and 1MHz (1 million cycles per second) to encode data.
Since ADSL does not need the voice range and voice certainly doesn't use the high frequencies of ADSL, the two can happily coexist as long as the high-frequency noise is filtered from the voice circuits. In other words, you can talk on the phone at the same time you use ADSL.

How Are ADSL Tones Filtered From Voice Lines?

ADSL high-frequency tones are filtered using a low-pass filter device. This device may either be installed outside by the telephone company in a separate box with a dedicated line going to the ADSL modem, or the filtering can be achieved within your facility using special little inline filters that plug between your phone device (telephone, fax, modem) and the jack in the wall.

What Lines Should I Submit To Test?

Only submit telephone lines that you expect to keep. ADSL depends on voice service on the same line, so do not submit a modem line for testing/approval if it is your intention to get rid of it when you get ADSL! We had one customer whose voice line did not qualify, but the modem line did so they ordered a disconnect on the modem line seeing they were getting ADSL. You guessed it! The ADSL order was halted immediately.
Only submit voice-grade telephone lines. ADSL cannot use ISDN lines and cannot use trunk lines. Suitable lines are regular voice lines, fax lines, even modem lines if you expect to keep them after getting ADSL.

Why Does My Line Not Qualify For DSL?

Your line may not qualify because of a number of reasons. First and foremost, you might not be within the range required to serve DSL from the DSLAM (generally within 3.5 miles of line). Another reason might be that your telephone service is being serviced by a CLEC other than BellSouth (e.g. BTI, Trivergent, etc.). Our circuits can ONLY be installed on BellSouth lines by telecommunications law.
Your neighborhood may be serviced by a fiber feed which causes DSL problems unless equipped with special additional equipment. Additionally, your lines may have bridge taps or load coils (see above) which prevents ADSL from traveling on them. Finally, your line might not be in the line database at this time and may qualify later on.

My Line Qualified - What Do I Do Now?

Do nothing apart from placing your ADSL order with Netpath, Inc. The fact that your line qualified does not mean that you will actually get ADSL to work on your line. Do not get rid of your modem line or ISDN until ADSL is up and has been running for several days. There are several reasons for this:

1. The line database could be incorrect and there might be conditions on your line that were unforeseen.
2. The line database could be incorrect and you are out of range.
3. There might be adverse conditions surrounding your line (e.g. noise or shorts).

Especially, DO NOT EVER DISCONNECT THE LINE THAT QUALIFIED FOR THE ADSL. ADSL depends on there being a regular voice service on the same line. If you disconnect the line, then your ADSL will go away also.

What Does DSL Get Me?

DSL's claim to fame is high-speed access. Throw out any concepts that you have about surfing or downloading using a modem. DSL is much faster. Additionally, DSL service is up 24 hours per day. This is true high-speed, unlimited time usage.

What Do I Need For DSL?

DSL is provisioned using a special device which we will call a "modem" for want of a better term. Netpath has standardized on the 3-Com Home Connect and 3-Com Office Connect products, both of which are 10 Mb Ethernet-based devices. What this means is that you need to have an Ethernet network card in your computer. If you do not have one, you will need to purchase one and install it. These are relatively inexpensive. If you have questions, please contact us and we can help.

What About Security and Hackers?

Since DSL is a 24 hour per day option, your computers are vulnerable on the Internet. You might wish to purchase a Linksys Cable/DSL Router which has a built-in firewall. There are two models to choose from:

BEFSR11 which has only one port, and BEFSR41 which includes a 4-port hub (see http://www.linksys.com/products).
Another solution is to use port-blocking software such as ZoneAlarm (free for non-commercial use) which can be found at http://www.zonealarm.com and downloaded.

A VERY important step to make in preparing your system is to make sure that either ALL shared devices are properly password protected OR to remove sharing from TCP/IP. If you need to share drives and printers, then it is better to install NETBEUI for sharing in Windows. In TCP/IP settings, click on Bindings and turn off File and Printer Sharing. This is a major hole that hackers can exploit.
It is also advisable to apply any security fixes to your operating system from the manufacturer (Microsoft, Apple, etc.) to ensure known holes are plugged.

How Many Computers Can I Run On DSL?

We automatically give you 4 IP addresses which you can use on different machines within your network. If you are running behind a proxy server, firewall, or Linksys device, then you can add as many computers as the DHCP server will handle. The IP addresses that we provide are real static IPs.

So I Ordered DSL, Now What?

Once contracts and permissions have been signed, Netpath places an order for ADSL to your location. The telephone tech will check for DSL at the outside connection and then the order will be marked complete. Once Netpath has received a copy of the completed order, one of our techs will contact you to set up a time to install the DSL modem and help set up one of your computers to use it.

How Do I Reset My HomeConnect Modem?

Do NOT EVER press the reset button on the back - it resets the configuration of the modem. To reset /reboot the modem, merely unplug it and plug it back in.

Troubleshooting An ADSL Connection

The most important first step is to check all connections to the ADSL modem. If they are snug, make sure that your computer's Ethernet is connected. On the HomeConnect, you should see a green power light, a green ADSL indicator, and a green LAN light. The LAN light and ADSL lights might blink on and off occasionally.
If the LAN light is not lit, then your Ethernet is not correctly connected. On a HomeConnect you might have accidentally switched the modem from crossover to straight-through or vice-versa, if all of your cables appear to be snugly plugged in. There is a small transparent plastic switch next to the Ethernet connector on the modem. Press it in and then release it to change the configuration. If the Ethernet light does not come on, press it in again and set it back as it was. Reset/reboot the modem by unplugging it and plugging it back in. If this does not change the Ethernet light within a minute, something is broken on the Ethernet side.
If the ADSL light is red, then there might be something wrong with the ADSL connection. Check the connection to the phone plug. Reboot the modem. If the ADSL light does not turn green in 2 minutes, then something is wrong with the ADSL connection.