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6.0 Terminology

The Asymmetric Digital Subscriber Line is your existing telephone line. Asymmetric means that the data transfer speed is not the same in both directions. Typically the downstream is at least four times the upstream speed.
Bell Sympatico currently offers ADSL.
The maximum theoretical throughput of ADSL is 8mbps down, 1mbps up.

ADSL is a distance-sensitive technology: As the connection's length increases, the signal quality decreases and the connection speed goes down. The limit for ADSL service is 18,000 feet.

1Mbit - 4.8KM
3Mbit - 3KM

Your ISP may also turn on interleaving for error correction depending on your lines condition.

by BliZZardX See Profile edited by MacGyver See Profile
last modified: 2003-12-02 21:58:17

Interleaving is an extra level of error correction.

ADSL modems are capable of data interleaving, which is a technique used to increase resistance to noise bursts on a line. Interleaving decreases the chance that noise on a line will cause data transmission errors. Interleaving may be necessary in situations where the quality of the phone line is sub-standard or you are approaching the distance limits of DSL service to ensure a stable and reliable connection.

The down-side of interleaving is that it increases latency (ping). This is because a single packet is spread out over several packets before it can be fully sent or fully received.

You can tell if interleaving is active on your line by measuring the first hop ping. If it is under 20ms, interleaving is disabled. If it is above 40ms, interleaving is enabled.

The DSLAM (central office equipment) has interleaving set, and this cannot be changed remotely by the end user. In general, only people who need interleaving have it turned on. However, some technicians will turn it on as a "quick fix" for problems that could be best solved in different ways.

If you would like to have interleaving turned off, please refer to instructions located here. Bear in mind that if your line quality is poor, Sympatico will likely not turn it off. However, if you insist, they will change it, but you must agree to forgo any future support regarding speed or interleaving changes. They will flag your account so that any rep who helps you will see they are not to support you any more.

After all is said and done, your modem should go offline and re-sync.
You will notice lower ping times.

IF after interleaving is disabled, and you experience line quality problems, slow speeds, or connectivity issues, then interleaving is likely required on your line for DSL to work properly.

A more detailed explanation of Interleaving can be found by clicking here
A thank you goes to kevmetric for the information.

by BliZZardX See Profile edited by MacGyver See Profile
last modified: 2005-03-27 16:39:14

ATM network
ADSL products typically use ATM (Asynchronous Transfer Mode) to carry data cells from customer modems to DSLAMs. When this traffic arrives at a DSLAM in a local exchange, it is normally carried over an ATM network to a more central location within the network with internet access.

by BliZZardX See Profile edited by MacGyver See Profile
last modified: 2003-07-26 22:04:38

The DSL Access Multiplexor is name for the bank of ADSL modems in the central office where your DSL line terminates. Before reaching the DSLAM, your line is passed through an exchange-side splitter/filter where the line is split in two: the original line goes to the telephone switch, while a new line goes to the DSLAM.

If the DSLAM is located in a cabinet in your neighbourhood (not in the central office), it is referred to as the RDSLAM

by BliZZardX See Profile edited by MacGyver See Profile
last modified: 2009-01-12 15:02:59

Sometimes referred to as "Stingers" (a Lucent Technologies trademark), a Remote DSLAM, RSLAM, or RDSLAM is a DSLAM that is not installed in the central office. Instead it is installed in a pole mounted box or a steel cabinet on the ground, somewhere along the phone line between your central office and your home. RDSLAM's are installed to decrease the distance between your DSLAM and your modem, thereby improving service by reducing distance. Your voice telephone service is still routed to the central office.

by MacGyver See Profile
last modified: 2004-03-10 17:13:10

Occupancy is the percentage of line capacity used. Each DSL line is capable of a certain maximum speed or "capacity" dependant on line distance and other varying factors. The occupancy is an expression of your current sync rate setting over your maximum capacity. There are occupancy rates for both upload and download.

For example, if your current sync rate is 3008/800, and your maximum capacity is 7200/1100, your occupancy is 42% downstream and 72% upstream.

Bell Sympatico will not upgrade your line if the occupancy if either the download or upload sync rate needs to be increased and is already 70% or more.

You can find out what your occupancy is by checking your modem line stats if your modem supports that features, or by calling 310-SURF and speaking with an agent.

Also known as "Line Occupancy" or "Relative Capacity Occupation"

by MacGyver See Profile
last modified: 2005-02-10 08:33:40

Outside Plant Interface Digital Subscriber Line Access Module

Bell uses this term to refer to the new Lucent Stingers, which is a RDSLAM.

Bell and Lucent joined together to develop these RDSLAMs. They are custom built for the extremes of Canadian weather.

by MacGyver See Profile
last modified: 2004-04-30 15:31:55

The demarcation point (or demarc or Network Interface Device (NID) for short) serves several purposes:

•It is the point that defines the end of the telephone company's wiring, and the beginning of your wiring.
•It defines where the telephone company's responsibility for maintenance ends, and your responsibility begins.
•It contains a surge suppressor to help protect the wiring and connected equipment in your home from damage
•It allows you to temporarilly disconnect your wiring from the telephone company's wiring for troubleshooting purposes.

Generally, the demarc is located on the exterior of your home in a grey or black box. Sometimes the demarc may be inside your home in the basement if you live in an older home. If you live in an apartment or condominium, the demarc is usually located in the main telephone room, although in some buildings it may be located in your suite, behind a blank outlet cover plate or in a closet or utility room for example. If you live in a townhouse, the demarc may be located in a common cabinet outside at the end unit.

Maintenance of the demarc itself is the responsibility of the telephone company.

More photos available here:

by MacGyver See Profile
last modified: 2004-07-11 18:32:27

AML stands for Added Main Line.

AML is technology used by Bell to piggyback a second voice line on an existing pair of copper wires serving an existing voice line. AML lines do not support DSL services. Getting the AML removed may be difficult especially if there are limited numbers of wire pairs in your neighbourhood.

by MacGyver See Profile

(for ease of explanation, the example is if a user is connected to a terminal in a central office -- the same scenario applies if they terminal is remotely located outside the main central office of the area)

An ADSL modem connects to a DSLAM (Digital Subscriber Line Access Multiplexer) in a central office over your phone line and "handshakes" with it in a manner somewhat akin to that of a dialup modem in that when making the connection, it sends various connection speed requests back and forth until they can agree (for lack of a better term) on what will work for the equipment at both ends. When the speed is agreed upon, the modem "syncs" in that it is ready to send and receive at the same connection rate as the DSLAM.

The rate that it connects at is determined by two things:

(a) the rate that it is set at by the company that owns the DSLAM (in our case Bell, on behalf of the ISP in question)


(b) any line problems that might affect speed (they cause resistance and can hinder communication -- think of it as static on a line when trying to talk to someone; if it is clear, your call goes faster than if it is noisy and you lose bits of the conversation).

As distance is a problem with ADSL (the longer the loop, the greater the resistance in transmitting date), the farther you are from a DSLAM, the lower your maximum rate of communication. This is why some people can get higher speeds than others (or at least, higher estimated speeds).

We are in the midst of an upgrade, but we'll leave that aside for a moment. Right now, there are three speeds of ADSL available: DSL Basic (128k), HSE (2500k or 2.5M) and HSE Ultra (4000k or 4M). Depending on which one you have, they modem will try to connect at the appropriate speed for your service. However, if there are problems, the modem may "jump down" to the next sync rate to try and stabilize your connection instead of having it try to connect at a speed which it cannot manage. This is why the service is marketed at 'up to' rather than guaranteed speed.

Explanation courtesy of Kardinal See Profile

by MacGyver See Profile

Refer to this post for an explanation.

by Kardinal See Profile edited by MacGyver See Profile
last modified: 2005-06-12 07:45:39