2. Installation

Before actually ordering service, there are several things you may want to explore.

2.1. Pre-Installation

Beyond the obvious consideration of price, there are many reasons to investigate which providers may be offering DSL services in your area. The large Telephone companies are everywhere, and may advertise the most. But increasingly smaller ISPs and independents are getting into the act. This is creating diversity in the DSL marketplace. A good thing of course, but possibly creating a little confusion too.

Not all DSL services are alike. Just because two local companies are offering "ADSL", does not mean that necessarily there is much in common at all. In fact, there are potentially a number of factors that make one ADSL provider's service significantly different from another's. Some things to consider:

For a more lengthy discussion on some of these considerations and related issues, see the DSL Overview appendix for more on modems, qualifying for service, and choosing a provider.

Once you have chosen a provider, and ordered service, the next step is for the telco to "qualify" your loop. This essentially means testing your line to make sure it can handle the DSL signal, and possibly what level of service may be available to you. This may take some time, especially if the telco encounters problems with the loop. If no problems are found during this phase, then possibly there will be a two to three week wait for the installation. YMMV.

After the telco has qualified the loop and readied their end of the connection, the next step is installation of the necessary components at the customer's end of the connection: wiring modifications, splitter or filters, and, of course the modem and any necessary software.

2.2. Installation Options -- Self Install or Not

You may or may not have a choice on how the installation is done, or who does it. This is totally at the discretion of the provider. Many providers offer a "self install" option where you do all the work. In this scenario, the provider will send a kit in order to save them from sending a tech, and thus reducing cost. Typically, self install kits will include microfilters for the POTS (Plain Old Telephone Service) phone jacks, the modem (and maybe a NIC), and a CDROM with drivers, etc. on it. In some cases, a splitter may be included instead of microfilters. In any case, some type of filtering is necessary on the non-DSL lines. If not the noise generated by the DSL signal may interfere with POTS devices.

The other possibility is for the provider to do the installation. Obviously, the cost is higher here, but it may have the advantage of having a trained tech do any wiring. There is also a better chance of getting a "splittered" installation with this option (a good thing!). Another benefit is that if something is wrong with the line, or the telco has not provisioned the line properly, an on-site tech may be able to help sort out certain kinds of problems quickly.

The self-install kit should come with full instructions, regardless of whether the installation will be splittered or filtered. So we won't go into much detail on this aspect.

2.3. Wiring/Installation Options

There are various wiring schemes depending on how your service is being provided, who is providing it, and which DSL service is being provided.

Figure 1: DSL Block Diagram, POTS with Splitter (NID not shown)

       <--------Home/Office-----><---Loop---><--Central Office-->

 POTS  X-------+
 phone,        | 
 fax,          | 
 etc,          | 
               |                                 CO
               |                               -------
               |                               |     |
               |                               |     |
               |            -----              |     |
 POTS  X-------+----Voice--=| S |              |  D  |
                            | P |              |  S  |=- Voice Switch
                            | L |    2 wire    |  L  |
                            | I |=------------=|  A  |
                            | T |  Local Loop  |  M  |=- ISP --> INET
           ---------        | T |              |     |
 Linux X--=| Modem |=-Data-=| E |              |     |
           ---------        | R |              |     |
                            -----              |     |


Figure 2: DSL Splitterless (a.k.a. filtered) Block Diagram

       <--------Home/Office-------><----Loop---><--Central Office-->
 POTS  X--Voice---[RJ11]------+
 phone,          (filter)     | 
 fax,                         D                      CO
 etc,                         a                    -------
                              t                    |     |
                              a                    |     |
 POTS  X--Voice---[RJ11]----- &                    |  D  |
                 (filter)     V  -----             |  S  |=- Voice Switch
                              o  | N |   2 wire    |  L  |
                              i-=| I |=-----------=|  A  |
                              c  | D |  Local Loop |  M  |=- ISP --> INET
                              e  -----             |     |
           -----------        |                    |     |
 Linux X--=|  Modem  |=-------|                    |     |
           -----------                             -------

2.4. Self Install - Wiring

If you are not doing the self-install option, then you may skip this section and move to Configuring Linux. If you are doing a self-install with microfilters, skip to the mircofilter section. The following procedures are meant to illustrate the wiring process. Please note that your procedures may be different at your location. Make sure you follow any warnings or safety instructions provided, that you RTFM, and that you are familiar with telco wiring procedures.

The first step will be to wire up the connections from your provider. Identify the line on which service will be installed, and the locations of your splitter and DSL jack(s). (For perhaps a better wiring scheme, see the Homerun section immediately below.)

Be aware that typical telco wire has more than one pair per bundle. Often, two pairs, but sometimes more. If you have but one phone line, the other pair(s) are unused. This makes them available for use with wiring for DSL. Wire pairs are color coded for easy identification. SDSL and IDSL require a dedicated, or "dry", pair. If an unused pair is available, then no real re-wiring is required. It is just a matter of re-wiring an existing jack for the correct pair of wires, and attaching the modem.

2.4.1. The Homerun


" I would not use microfilters if I lived across the street from my CO. A splitter is the only way to go. "

--A retired BellSouth ADSL installer  

The optimum method of wiring for the DSL modem is sometimes called a "homerun". It is called this because it is one, straight shot from the splitter to the modem's DSL jack. What this does is bypass the existing inside wiring altogether, and any problems that might be lurking there -- like a corroded connection somewhere on a POTS jack. Inside wiring deficiencies can cause a degradation of the DSL signal.

This also allows you to route the cable to avoid any potential RFI (Radio Frequency Interference) sources. RFI anywhere in the circuit can be a DSL killer. Routing the cable away from items that may have electric motors, transformers, power supplies, high intensity lighting fixtures, dimmer switches and such, is a smart way to go. And you are also less likely to have a failing microfilter cause problems -- one potential point of failure instead of several. You can also use a better grade of cable such as CAT 5.

If your existing installation is "splitterless" (i.e. using microfilters) now, converting to a homerun will entail purchasing a splitter. And, of course, will also mean some new wiring will need to be run. Microfilters also add to the effective loop length -- as much as 700 ft per filter in some cases! So if you have several microfilters installed, and your sync rate or distance is marginal, eliminating these filters may result in a significant improvement.

A poor man's splitter can be rigged by using a microfilter inside the NID. This is not "by the book", but seems to work for many.

2.5. Wire the Splitter

If you have the splitterless design (i.e. using "microfilters") or a dedicated line, you may skip this part.

The splitter will typically consist of two parts, the splitter and a small outdoor housing. Mount the splitter and accompanying housing per the telco's instructions at the Network Interface Device (NID) point (also sometimes called the SNI or ONI), usually the side of your house where the phone line is located. Put it on your side of the NID. The phone company may need to access the splitter for maintenance, so its advisable to locate it on the outside where they can get at it, but outside is not absolutely necessary.

The wire bundle should have at least two separate wire pairs. The splitter takes one pair, and separates the signal onto two pairs. One pair in the bundle will then go to all POTS jacks, and the other to the modem's DSL wall jack. So connect the incoming telco line to the LINE side of the splitter. Then wire the inside pair for your telephone to the VOICE, and your inside wire pair for the modem to DATA.

Checkstep At this point, you should be able to pull dial tone off the voice side of the splitter. If this doesn't work, then you've wired it wrong. You can also plug the modem into the test jack in the NID box (most should have this). Plug in the modem's power cord, and if the line is provisioned correctly, you should "sync" in less than a minute. This test only requires the modem. (Internal and USB modems will require a driver to be loaded before syncing. This would mean having the computer there too.)

2.6. Wire the DSL Jack

Wire the DSL wall jack (RJ11) at your computer location, which should already be connected to the DATA side of the splitter. The specifics differ for each situation, but basically you will have a wire pair that you will connect to the DSL jack. Make sure you read the directions, as the DSL-RJ11 wiring may be different for phones and DSL jacks. AND -- different modems may expect the signal on different pairs -- most on the inside pair, but some on the outside pair.

Figure 3: RJ11 Wiring options

   /  \
  |    |  
    ^^  <-- Inside     Most modems on inside pair
   ^  ^ <-- Outside    Some on outside, e.g. Alcatel 1000, SpeedTouch Home


2.7. Installing Microfilters

Pretty much a no-brainer here. If you are doing a "splitterless" installation, then install the provided microfilters in all phone jacks except the one where the DSL modem will be connected. Don't forget devices like fax machines and analog modems. The filters filter out the higher DSL frequencies and will keep the DSL noise from interfering with POTS equipment.

Warning! If you have an alarm system, it is recommended not to use microfilters. Alarm systems can present various problems, depending on how they are implemented. The recommended installation in this case is with a splitter.

2.8. Installing an Ethernet Modem

To install, connect the modem's (or router's) power cord, and connect the phone line between the DSL wall jack and the modem. This cable should be provided. If not, a regular phone cord will suffice. With the ethernet interfaced modems, you may also connect the ethernet cable between the NIC and the modem (but not really necessary at this point just to verify an ethernet modem is working).

Checkstep At this point, verify that the modem syncs with the telco's DSLAM signal. Most modems have a green LED that lights up when the signal is good, and red or orange if not in sync. The modem's manual will have more details on the LEDs. If it doesn't sync, then check your wiring, or make sure that the DSL signal is being sent. Do this by calling your telco and verifying they have activated the service. Or by testing the modem at the test jack on the NID (see above). Note that having dial tone on the line does NOT confirm the presence of the DSL data signal. And vice versa -- perfectly possible to have dial tone and no DSL, or DSL and no dial tone. There should also be no static or noise on the voice line when everything is installed and functioning properly.

2.8.1. Installing the Ethernet Network Card (NIC)

Ethernet modems will, of course, require an ethernet network card. If you haven't already done so, install the NIC in your Linux machine, configure the kernel, or load modules, etc., etc. This is sometimes the biggest stumbling block -- getting the NIC recognized and working. See the various Linux references for doing this, such as the Ethernet HOWTO for more information. Also, see the Troubleshooting Section below. This is certainly something you could conceivably do ahead of time if you already have the NIC.

Be sure the RJ45 cable between the NIC and the modem is now connected. You can "hot plug" this cable, meaning there is no need to power down to do this.

We can do a few quick tests now to see if the NIC seems to be functioning properly. First we'll attempt to bring up the interface. Then we'll see how well it is responding by pinging it. And lastly use ifconfig to check for errors:

# ifconfig eth0 up

$ ping -c 50
PING ( from 56(84) bytes of data.
64 bytes from icmp_seq=0 ttl=255 time=0.2 ms
64 bytes from icmp_seq=1 ttl=255 time=0.2 ms
64 bytes from icmp_seq=2 ttl=255 time=0.1 ms

- ping statistics -
50 packets transmitted, 50 packets received, 0% packet loss
round-trip min/avg/max = 0.1/0.1/0.2 ms

$ ifconfig eth0
eth0    Link encap:Ethernet  HWaddr 00:50:04:C2:09:AC  
        inet addr:  Bcast:  Mask:
        RX packets:428 errors:0 dropped:0 overruns:0 frame:0
        TX packets:421 errors:0 dropped:0 overruns:0 carrier:0
        collisions:0 txqueuelen:100 
        Interrupt:10 Base address:0xc800 

If "eth0" comes up without errors, and you can ping it without errors, and ifconfig shows no errors, we should have all our hardware in working order now, and are ready to start configuring Linux. If not, see the Troubleshooting section below.

Gotcha: A few modems may already be wired as a 10baseT crossover, and require a direct Category 5 cable for a direct connection to a NIC, rather than a crossover cable. I lost around 12 hours figuring this one out, so don't make the same mistake - make sure you RTFM first.

2.9. Installing a USB Modem

The physical installation of a USB modem is similar to an ethernet modem. There is no ethernet card necessary obviously. So connect the phone line between the DSL wall jack and the modem's DSL port, and attach the USB cable to the computer's USB port.

USB modems will require vendor and model specific drivers in order to sync and function properly. Assuming you are using the Alcatel SpeedTouch USB, then there are drivers available from Alcatel's driver page: http://www.alcatel.com/consumer/dsl/supuser.htm#driver. This driver is a kernel module, and is available as both binary and raw source. This driver requires at least a 2.4.1 kernel. In addition, you will need to install additional software and patch the kernel for other required features. There are brief instructions included with the driver. Much of the code is still experimental, and reportedly is not completely stable at this time. This is not novice level stuff!

This driver also supports both PPPoE and PPPoA, though the steps for getting either to work are quite different. See the Appendix for step-by-step instructions.