DSL Frequently Asked Questions

What is DSL?
DSL (Digital Subscriber Line) is an always-on internet connection that normally terminates in a socket on your wall, one that looks much like a phone socket. In the US, the socket is exactly a phone socket, and, for the popular residential DSL, (ADSL), the same housewiring does indeed carry both phone and data.
 
DSL is billed on a monthly basis, usually for a fixed price, and for the majority of providers it includes unlimited usage. In other words, whether you use it for email once a day, or you are a net addict and use it constantly, your bill is always the same.
 
Once you have a DSL line, you can use all the resources of the internet in the same way as you did from a regular modem and a dial-up account. The difference is now you can use them 24 hours a day with no connection delay, and usually (although not always) without a 'username' and 'password'. You need not worry about busy signals or any connection/disconnection process.
 
The key advantage of DSL over a dial-up modem is speed. DSL is from several to dozens of times faster than a modem connection. A complex web page that could take up to a minute to finish loading at 56K can appear in just seconds over DSL.
 
Connection speed, reliability, and the 'always-on' nature of DSL are the main reasons it is so popular. For small businesses, DSL is also a great way to save money compared to pay per minute ISDN service, or expensive T1 lines.
DSL vs CABLE?
This is a question that is asked everywhere you look. Which do I want ... DSL or Cable?
 
DSL service shares bandwidth amongst ALL users connected to the same DSLAM. Cable shares bandwidth amongst ALL users connected to the same CMTS.
 
DSL's advantage?
The dedicated circuit prevents other users from affecting your connection to any significant degree. (In most cases.)
 
Cable's advantage?
Generally cable can support higher bandwidth rates, and can usually provide service to a larger area than 18,000 wire-feet, DSL's limit.
 
Cable modems are typically faster for downloads than most if not all DSL lines, when the cable infrastructure is new or well maintained. One of the most common complaints seen is that of slower connections and other problems as more subscribers in a given area come on line. Additionally, cable has a few other disadvantages when compared to DSL.
 
The first disadvantage is that cable is an RF network -- this means that it is vulnerable to transient problems "within the network" from RF interference. Since cable is a shared media, there is a possibility that performance may degrade over time as additional households plug in, connect additional devices (videos, game machines etc.) to the TV lines.
 
A cable company may react slowly to decreases in performance if it reacts at all, as they never sell access by speed, or promise consistent speed or latency.
 
Another of the disadvantages of cable over DSL is the upstream (return path). Cable companies are using a very narrow band for return signalling, and this is positioned below all the space allocated for TV channels. This band is prone to RF interference and is very limited in capacity. Upstream transmissions may therefore compete with others in the area, get delayed (suffer high latency) due to noise fighting techniques, and cable TOS (Terms Of Service) typically prohibit any kind of constant upstream use. Internet use is shifting away from central servers broadcasting to many individuals and some interesting peer to peer applications are appearing (games, voice and video applications, communal libraries). These applications need a strong upstream channel.
 
In summary, cable modems are currently good value and strong competition for residential casual use, often available more cheaply and far faster than their ADSL competition. However, DSL is probably the more future-proof system, offering digital direct from the internet infrastructure. If your DSL ISP is on the ball, your performance in either direction will not be different from peak hour to early morning, and DSL lines are available for a wide variety of purposes, both business and residential.
Why is distance important with DSL?
PShift currently only offers DSL in Stowe and Morrisville, and this offering is contingent upon your distance from the telco office. Your phone lines normally terminate at a telco office, usually nearby. This distance, (the length of your line between your location and the telco office), is a very important factor in whether or not you can get DSL, and what speed you can get.
Here are some rules of thumb for distance ranges. Please be aware that especially with non-Telco ADSL lines, distance limits for speeds can vary widely from company to company. There are cases where it is policy for "residential" DSL lines not to be offered as far out as functionally identical "business" products!
Distance
In Feet		 comment
less than 5000 You will have little trouble getting all speeds of DSL
5000-10600 You may have trouble getting the highest speeds on offer
10600-15000 The danger zone for DSL from national CLECs like Covad and NorthPoint. Speeds on offer are pinned back steadily until they reach 192k for 15,000 feet. If your line is longer than around 15000 feet, they may not accept an order.