DSL HOWTO for Linux
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# 2. Installation

Before actually ordering service, there are several things you may want to explore. Please note, that there are many ways any given telco might decide to handle qualification and installation procedures. Much of what is described in this section, is how it is commonly done in the U.S.

## 2.1. Pre-Installation

In many parts of the world, there is no choice on who you get DSL from: your friendly local telco, of course! They own the copper wires, and thus they hold all the cards.

However, in the U.S. de-regulation has opened this up somewhat. Beyond the obvious consideration of price, there are reasons to investigate which alternate 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 has created some diversity in the DSL marketplace. A good thing of course, but possibly creating a little confusion too. Conversely, in areas where there is only one choice, then we have no choice but to accept whatever service is being offered.

If your telco has a monopoly on phone service and DSL, you may skip the rest of this section. And probably the next few sections. They will probably control the installation and qualification processes, and you just wait for them to get finished.

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:

- Speed vs Price.

- What hardware is provided, i.e. modem or router. It is best if this is external ethernet in either case.

- The ISP's Network architecture. PPPoX? Static IP? Servers allowed?

- Is it an "always on" service, at least theoretically? Are there supplemental usage fees, or idle timeouts?

- Linux friendly, Linux hostile, or Linux agnostic? This is not as much of a problem as it used to be in most areas. Some providers are still very restrictive on allowing "servers", and possibly even LAN connections. Buyer beware. Talk to other users, and read their TOS (Terms of Service) to get a feel for their attitude.

- Quality of service. How is news, mail, etc.? News particularly seems to be inconsistent with low-end broadband providers. Probably because of the dramatic increase in binary news content, which is compounded by the higher bandwidth and increased usage of such groups.

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 one 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. In much of the world, this is done by the telco, and there is little flexibility. Many providers in the U.S. 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) or ISDN (where ADSL over ISDN is used) 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 regula telco devices such as phones and answering machines.

The other possibility is for the provider to do the installation. Again, this may be your only option. 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. If your telco is performing the installation, you may skip this section.

- Dedicated Line. Some DSLs require a dedicated, or "dry", wire pair, e.g. IDSL. This means a separate, physical line without dial-tone for DSL and Internet connectivity. Also, DSL services from CLECs (independent telcos like Covad), may use a dedicated line, depending on their line sharing agreement with the local incumbent carrier. (Instead the CLEC will actually lease a loop from the ILEC.) On your end, this simply means using one of the unused wire pairs in the telco wire bundle, and connecting it to the DSL jack.

- Shared Line with Splitter. For DSLs like ADSL, that are provided over the same line as regular voice service, the signal must be filtered somehow so that voice services are not adversely effected. Installing a splitter splits the line into two pairs, and filters the DSL signal from one of them. This results in a inside wiring scheme where DSL goes to only one jack, and then regular voice type service to all other jacks. This is considered by many to be a better type of installation than "splitterless", i.e. with microfilters instead. See below.

  Splitters are available from various manufacturers and come in various shapes and sizes. Some are small enough to fit in the NID itself (sometimes called SNI, this is the telco phone box on the outside of your house), while others have a housing as large as the NID itself. Typically this is mounted near the NID, on the customer's side of the demarcation point.

- Shared Line with Filters. Again, for some DSLs that piggyback on the POTS (or ISDN) line, the signal must be filtered or split at some point. This is not necessary for g.lite or RADSL however. The other way of doing this is by placing RJ11 "microfilters" in each phone jack -- except where the DSL modem will be. These filters are relatively small, plug-in devices and remove the higher frequencies associated with DSL. This is obviously much easier since no tools or wiring is required. This is often what is included in self-install kits, and is often referred to as a "splitterless" installation. This is a very common approach in the U.S. Note that in areas where ADSL over ISDN is provided, filtering is required also, but the filters themselves are quite different and are not interchangeable with POTS filters!

  Similar microfilters are sometimes used by some telcos to reduce the excessive "whine" on the line that is produced by some modems. This is a little different approach as the filter is put on the same jack as the modem.

- Shared Line, Splitterless and Filterless. Some newer DSLs, like G.Lite, have no adverse effect on regular POTS devices and thus require no filters or splitters. This would seem to be the wave of the future. Just plug and play. Though still not very common.

### Figure 1: DSL Block Diagram 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 a self-install, 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 voice 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 just fine 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 phone 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

``

||
||
||
/ \
|RJ11|
| |
----
||||
^^ <-- 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", self-install 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 (or ISDN) equipment.

Warning! Alarm systems can present various problems, depending on the type of alarm and how it is installed. This may require telco help for proper installation so the one does not interfere with the other. Common microfilters tend not to work because most alarm boxes use a different size jack. Filters are now available just for alarm boxes, though traditionally this has been handled with a splitter type installation.

## 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 10.0.0.1 up

    $ ping -c 50 10.0.0.1
    PING 10.0.0.1 (10.0.0.1) from 10.0.0.1: 56(84) bytes of data.
    64 bytes from 10.0.0.1: icmp_seq=0 ttl=255 time=0.2 ms
    64 bytes from 10.0.0.1: icmp_seq=1 ttl=255 time=0.2 ms
    64 bytes from 10.0.0.1: icmp_seq=2 ttl=255 time=0.1 ms
    <snip>

    - 10.0.0.1 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:10.0.0.1  Bcast:10.255.255.255  Mask:255.0.0.0
            UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
            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 most likely 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, this will require both a binary firmware driver available from Alcatel's driver page: http://www.speedtouchdsl.com/support.htm, and a separate modem driver.

This driver also supports both PPPoE and PPPoA, though the steps for getting either to work are quite different. See the Appendix for more on this modem.

The Eci Hi Focus ADSL Modem has some support in Linux now too. See http://eciadsl.sourceforge.net/.

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