About DSL

Your DSL connection is composed of a lot of different components at your house, at the telephone company and at EasyStreet. In this page we break down the components into 3 main groups, describe the pieces and how they work, and give you an ideas for fixing various problems. This diagram gives you a good overall picture of your DSL connection.

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Your DSL depends upon your Phone Line

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The phone line between your location and the DSLAM at the telephone company (Telco) must meet the following requirements:

  • The line must be All Copper
    • Only one phone number can be assigned to the line
    • No Digital Loop Carrier (DLC) or fiber connection between your home and the local Central Office
  • The distance must be less than 15,000 feet.
    (Current technology is increasing this distance, check with your telephone company what the limit is in your area.)
  • No loads, bridges, taps or other phone company devices on the line.

DSL uses the same Plain Old Telephone Service (POTS) copper phone line to transmit data that your regular analog modem does, but uses a digital and not an analog signal. This technology works by bypassing the analog voice system (and its limitations) altogether.

With DSL you use a special DSL “modem” (also called a CPE) to send a digital signal from your computer, over the copper wire to another special DSL modem at your phone company’s Central Office (the building where your phone line terminates). At the Central Office, the regular voice and telephone data that you generate by using your phone normally is split off and sent normally through the Public Switched Telephone Network (PSTN), and the digital signal from your computer is translated at the DSL modem at the Central office (called a DSLAM) and routed through a separate Data Network to our network at EasyStreet. At EasyStreet, we route your data out to the Internet.

In this diagram the splitter that separates the regular telephone signal from the DSL signal is shown as a different device, but in real life the splitter is usually built into the DSL equipment.

Because DSL is separated from your regular voice line, you can use your DSL to connect to the Internet, at the same time that you are talking on the phone or using your fax machine. If you have a phone line in your house that you use just for your modem, you may not need it any more!

DSL “Modulation”

dsl-modulation

DSL takes advantage of the unused bandwidth on your copper phone line. The first 4KHz are reserved for voice data. DSL adds a second set of frequencies to your line in the upper part of the sound spectrum and uses that part of the channel for data. The image shows a sample of the frequencies that data can use.

There are many different types of DSL technology, and each type splits up the DSL signal differently, but most of them follow the same general rules given above.

We generally call the device that translates the signal from a regular digital signal sent out by your computer into the high speed sound frequencies that communicate that signal over your phone line a modem, even though these devices are very different than analog modems. Since the basic function of the machine is similar to the concepts that people are used to we find the word modem to be handy short-hand, understood by most of our customers.

Because the high frequency digital signals that your computer sends with DSL can sometimes be heard on your telephone (and can interrupt your fax machine), it is a good idea to install filters between your wall jack and your telephone handset or fax machine. Use the filters that came with your DSL modem kit, and check the diagram that comes with them for installation information.

Splitter-Less DSL Equipment

When DSL was first implemented in our area Verizon would install a splitter on the outside of your house that separated the voice and data channels on your telephone line. Then they would wire the data channel to a special phone jack in your house for DSL. They stopped doing that after the first year or so, now both phone companies use a splitter-less design.

splitterless

Instead installing a special splitter on the outside of your house, or in your wiring closet, the splitter is now built into the DSL equipment provided by the phone company. This has cut the installation cost of the equipment, and most users find that the DSL signal doesn’t interfere with their regular phone lines.

If you do hear some additional static or noise on your lines it’s a good idea to install the filters that came with your DSL equipment. (Don’t install a filter on the DSL line going to your modem, that will filter out the DSL signal and break your connection to the Internet).

The Internet light on the Actiontec, the WAN LNK light on the Cisco modems, Modem light on the Fujitsu modems and the connection indicators only tell you whether your not your DSL modem is ‘trained’ or synchronized with the DSLAM (DSL Area Multiplexer) — the device that translates the DSL signal at the telephone company. This is the first part of your connection to the Internet, and it’s the only part of the connection that uses DSL technology.

If your connection lights indicate that your DSL is working, but you can’t get to the Internet, the problem can be with your computer; in the connection to EasyStreet; or in the connection from EasyStreet to the Internet.

DSLAM to EasyStreet, EasyStreet to the Internet

This is a handy over simplification of the complicated nest of fiber and switching devices that take the data from your DSL line from the DSLAM and send it out to the Internet. The boundaries of the EasyStreet network are surrounded by the green box. (Clouds are used whenever there are too many connections to draw them individually).

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The “Path” (DSLAM to EasyStreet)

In the DSLAM (DSL Area Multiplixer) the DSL signal is translated back into a regular digital signal and then forwarded through the telephone company data network. After passing through the telephone company data network, the data from your DSL connection is sent through a DS3 to EasyStreet. The path that your data takes from the DSLAM to EasyStreet is often called the Permanent Virtual Circuit (PVC) — phone company technicians often just call it “the path”.

This part of your connection is largely invisible you and to us here at EasyStreet. Generally problems in this part of the network are found by sending a set amount of traffic through the data network and checking different points along the network to see if it makes it through to the other side. It can be difficult to find problems in this part of your connection, and it frequently takes a 3 way conference call between EasyStreet, the phone company’s DSL repair, and you at your end of the connection to identify the problem.

EasyStreet to the Internet

At Easystreet the DS3 from the telephone company comes straight into our Redback DSL router. (We have multiple Redback routers, but your connection only terminates in one of them). The IP of the DSL router is given as your Gateway on your Account Information, and it is the first piece of equipment that you can ping.

The DSL router uses your IP and your MAC address to authenticate your DSL connection (so you don’t need to enter a username and password). As it’s name implies the DSL router sends your data through our network to our other routers that connect to our mail and web servers , or to our upstream Internet connections.

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