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| What is DSL? DSL stands for Digital Subscriber Line. It is an Internet access technology that brings high-speed connectivity to businesses and homes over ordinary copper telephone lines. There are many types of DSL available. __DSL refers to the different types of DSL such as ADSL, SDSL, and IDSL. For example ADSL stands for Asymmetric Digital Subscriber Line (click to see description of this service). How DSL Works. Traditional phone service (sometimes-called "Plain Old Telephone Service" or POTS) connects your home or small business to a telephone company office over copper wires (that are wound around each other and called twisted pair). Traditional phone service was created to let you exchange voice information with other phone users and the type of signal used for this kind of transmission is called an analog signal. An input device such as a phone set takes an acoustic signal (which is a natural analog signal) and converts it into an electrical equivalent in terms of volume (signal amplitude) and pitch (frequency of wave change). Since the telephone company's signaling is already set up for this analog wave transmission, it's easier for it to use that as the way to get information back and forth between your telephone and the telephone company. That's why your computer has to have a modem - so that it can demodulate the analog signal and turn its values into the string of 0 and 1 values that is called digital information. Because analog transmission only uses a small portion of the available amount of information that could be transmitted over copper wires, the maximum amount of data that you can receive using ordinary modems is about 56 Kbps (thousands of bits per second). (With ISDN, which one might think of as a limited precursor to DSL, you can receive up to 128 Kbps.) The ability of your computer to receive information is constrained by the fact that the telephone company filters information that arrives as digital data, puts it into analog form for your telephone line, and requires your modem to change it back into digital. In other words, the analog transmission between your home or business and the phone company is a bandwidth bottleneck. Digital Subscriber Line is a technology that assumes digital data does not require change into analog form and back. Digital data is transmitted to your computer directly as digital data and this allows the phone company to use a much wider bandwidth for transmitting it to you. Meanwhile, if you choose, the signal can be separated so that some of the bandwidth is used to transmit an analog signal so that you can use your telephone and computer on the same line and at the same time (source http://www.whatis.com/ - DSL listing). How DSL works with multiple users (The DSLAM or Digital Subscriber Line Access Multiplexer To interconnect multiple DSL users to a high-speed backbone network, the telephone company uses a Digital Subscriber Line Access Multiplexer (DSLAM). Typically, the DSLAM connects to an asynchronous transfer mode (ATM) network that can aggregate data transmission at gigabit data rates. At the other end of each transmission, a DSLAM demultiplexes the signals and forwards them to appropriate individual DSL connections. What DSL service is right for me? Choosing a DSL service depends on how you plan to use the Internet. There are three types of DSL currently offered through InfoWest. They are ADSL, SDSL, IDSL. Let's read about each one of them that way you will better know which service is right for you. What is ADSL? ADSL (Asymmetric Digital Subscriber Line) is for residential (home) or small business users. ADSL is called "asymmetric" because most of its two-way (or duplex) bandwidth is devoted to the downstream direction, sending data to the user. Downstream data is any data arriving on your computer from the Internet. Upstream data is any data leaving your computer destined to arrive at another computer somewhere out on the Internet. For a user with ADSL service, downloading will be faster than uploading data on the Internet. In fact, only a small portion of the bandwidth, usually less than half of the total downstream bandwidth, is available for upstream data activity. ADSL data rates are 384K (downstream) and 128K (upstream). This is usually written as 384/128 ADSL and must be 12,000 feet or closer to the phone company's central office. The next service level up of ADSL is 768/384 DSL. It, too, must be within 12,000 feet of the central office. Much of the Internet activity of small business or home users is downstream activity. ADSL is great for users who download graphics, multimedia, and other rich content that needs downstream bandwidth. These requests are usually require little upstream bandwidth. What is SDSL? Another variation of DSL to be widely used is SDSL or Symmetric DSL (digital subscriber line). The main characteristic of SDSL is that it is symmetrical, meaning an equal amount of bandwidth is available in both directions. In other words, downloading has the exact same data capacity as uploading. A typical use of SDSL would be a company running a web server at their office (web servers require upstream bandwidth so you would need the upstream capacity as much as the downstream capacity). SDSL can carry about as much data on a single wire of twisted-pair as can be carried on a T1 line. SDSL data rates offered through InfoWest are 192K, 384K, 768K, and 1.1M. What is IDSL? IDSL (ISDN DSL) is somewhat of a misnomer since it's really closer to ISDN data rates and service at 128 Kbps than to the much higher rates of ADSL. IDSL runs at 144 Kbps and must be located within 36,000 feet of the telephone company's central office (where the DSLAM is installed). IDSL will be used in areas where ADSL and SDSL are not available because of distance limitations. This means that users living approximately 21,000 to 36,000 feet from a central office probably will not have ADSL and SDSL services available for their use and will have only the IDSL option. One of the great features you get with DSL service is the capability to connect multiple computers using a single DSL connection. In other words, you can connect your office lan (local area network) to the Internet with DSL. You can connect your home network to the Internet with DSL. DSL is so cool. Where will DSL be available (in St. George and the surrounding areas)? Most of St. George City will have access to some type of DSL service. Distance will determine what level of services (whether it will be ADSL, SDSL, or IDSL) are available. DSL modems follow the data rate multiples established by North American standards. In general, the maximum range for DSL without repeaters is 5.5 km (18,000 feet). As distance decreases toward the telephone company office, the data rate increases. Another factor is the gauge of the copper wire. The heavier 24 gauge wire carries the same data rate farther than 26 gauge wire. If you live beyond the 5.5 kilometer range, you may still be able to have DSL if your phone company has extended the local loop with optical fiber cable. Contact InfoWest to find out exactly what services are available in your area. How is DSL different from other Internet access technologies such as Cable or Wireless? Internet access services such as DSL, Cable, and Wireless are direct competitors. Some of the technologies are not currently available in southern Utah. Currently (4-3-00) there are only two broadband technologies available - DSL and Wireless. There are advantages and disadvantages to each of these services. One of the advantages with DSL is you won't be competing for bandwidth with neighbors in your area. DSL is switched technology which has advantages over shared network infrastructures such as cable or wireless. What Type of Equipment will I need for DSL? InfoWest will be using DSL modems from Efficient Networks. To find out more about the specific modems, go to www.flowpoint.com Here are some of the features of the DSL modems: -Built-in 4-port Ethernet LAN hub -DHCP automatically assigns and manages LAN IP addresses -FlowPointTM NAT allows multiple devices on your network to share a single WAN IP address or allows mapping of existing LAN IP addresses to a range of WAN IP addresses -FlowPointTM Firewall prevents unwanted visitors from accessing your LAN -Multi-user sharing via Ethernet LAN |
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