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How does ADSL compare to SDSL?
Do you already have xDSL? Test your Connection Speed You may test your connection speed by going to BCTel's Test Page or DSLReports Test Page or MSN Speed Test. These pages have Web-based programs that will test your download speed. My favorite program for testing and monitoring connection speed is DU Meter. Get DU Meter here. Other programs
that can help you to test and monitor your connection speed are:
If you are not satisfied with your system's performance, you might try tweaking your MS Windows Registry. Improve your modem performance via Windows Registry Tweaks for DSL and Cable Modems After registry tweaks, you can expect an improvement in your modem or router's performance. See my Cable Modem Registry Tweaks for Philip Philipov's tweaks. Some people argue that there is only one setting that will improve cable modem and DSL modem performance, namely, increasing the DefaultRcvWindow in the Windows 95/98 registry and increasing the TcpWindowSize in the Windows NT/2000 registry (or increasing the TCP Receive Window or RWIN). The default in Win95/98/NT is 8K, and in Win2000 the default is 16K. Moreover, there is a dispute about whether to increase the DefaultRcvWindow above 64K in Windows98. But, aside from these disputes, I have found that all of Philip Philipov's Windows registry tweaks are safe and effective. These tweaks will almost certainly improve your performance. Go to my Austin RR Info page for Tweaks. Or if you just want to do the minimum tweaking (namely, increasing the TCP Receive Window only), see the Navas Group for their registry tweaks. Austin xDSL Users' SURVEY Please vote in our xDSL Survey. Or if for some strange reason you do not wish to vote, you may view the survey results below.Austin xDSL Users' FORUMS
Please
visit our forums
to discuss xDSL, cable modem and related topics. Post a question
or comment. General xDSL Information SDSL is based on proven technology that the telephone companies have been using for years for their T1 service (namely 2B1Q encoding), and with a dedicated always on SDSL connection, for the first time, it is economical for small businesses to do the following:
SDSL is packaged in a range of bandwidth configurations that include 144 Kbps, 160 Kbps, 200 Kbps, 416 Kbps, 748 Kbps, 1.04 Mbps, and 1.5 Mbps. One of the great features of SDSL is its scalability. With just one phone call, you can increase your speed starting from 144 Kbps up to 1.5 Mbps. In other words, the SDSL Router is software switchable, and each router can support the full range of connection options. For example, you can start off with a 200 Kbps connection and as your needs change, you may upgrade to a 748 Kbps connection. Verio charges a fee of $150 to process each upgrade or downgrade order. How does 1.5 Mbps SDSL compare to a T1? Well, SDSL should be very comparable to a T1 in terms of performance, since SDSL is based on the same technology as HDSL DS1 or T1 (namely, 2B1Q encoding). If a dedicated T1 is considered more reliable, it is due to the fact that when businesses purchase a more expensive connection, they expect a higher quality of service. At present, most ISPs provide very few guarantees for SDSL connectivity (or none at all), whereas, for T1 or DS1 connectivity, many ISPs and telcos will promise: (a) 99 percent up time, (b) guaranteed packet delivery rates of 90 to 97 percent, (c) no more than 120 to 150 ms latency on their routers and (d) proactive notification within 15 minutes if they fail to ping your router. Why are ISPs offering guarantees for DS1 and no guarantees for SDSL? In short, ISPs are positioning traditional DS1 or T1 as more reliable so that they can continue to charge exorbitant rates for 1.5 Mbps connectivity. In other words, if ISPs offered the same guarantees for SDSL that they make for the traditional DS1 or T1 service, no one would purchase the older DS1 technology.
How does ADSL compare to cable modems? DSL provides a dedicated service over a single telephone line; cable modems offer a dedicated service over a shared media. While cable modems have greater downstream bandwidth capabilities (up to 27 Mbps), that bandwidth is shared among all users on a single node. So, performance of a cable modem will vary, depending upon the number of people connected to your node. With xDSL, you have a dedicated line from your computer to your ISP's backbone network, so you are NOT sharing your connection. Using Time Warner's cable service, your Motorola Cyber SURFR Wave modem has the capacity to support a 27Mbps downstream and 680kbps upstream. But, for whatever reason, the modem is throttling down to about 1/10 of the downstream capacity of the modem. In my experience, the absolute best throughput is about 2.7 Mbps downstream and 400 Kbps upstream. See my Austin RR Info for more information on Time Warner's Cable modem service in Austin. I have found cable modems and ADSL to be about equal in performance. If one has a performance problem, typically, the problem is caused by your ISP's network (i.e., problems with routing and latency). Again, your modem's performance is very much a product of your ISP's network peformance beyond your local node. And, some ISPs work harder than others to improve latency (or ping times) by (going beyond just connecting their network to the local NAP and) setting up private peering arrangements with major backbone providers. RR is constantly working on their network, trying to improve latency and routing. Likewise most xDSL providers in Austin have fairly robust networks as well. You may be able to find an ISP that has slightly better routing and latency than Road Runner, but most users will find that the peformance of RR and ADSL providers to be about equal. What do I need to get DSL? DSL uses exiting copper telephone lines, but transmits data at higher frequencies (i.e., 26kHz to 1 MHz) than what is used for normal analog voice and data traffic (i.e., 300Hz to 3,400Hz). Hence, the first prerequisite for getting DSL in your area is a high-quality telephone line. Also, you need to live within 10,000 feet from your local switching center to get the higher connection speeds (and 18,000 feet to get DSL at any speed). So, first, you will need to contact your telco or an ISP to see whether or not you qualify for DSL service in your area and at what speeds you may connect. Second, you need a connection from a telephone company (NorthPoint, Covad, Southwestern Bell...) and an Internet Service Provider to provide access to the Internet. Third, you will need to install in your computer a NIC (Network Interface Card). Fourth, you will need a DSL modem or a DSL router. Where can I get DSL in Austin? ADSL: There are several Internet Service providers in Austin who provide ADSL service (e.g., Texas.net, Jump.net, Swbell.net, io.com). Typical cost for 1.5M downstream and 128k upstream ADSL is $40 to 50 per month ($20 per month for the ISP and $30 per month to Southwestern Bell or Covad for the telephone line). For 6.0M downstream and 384k upstream ADSL, be prepared to pay $160 per month ($60 for the ISP and $100 per month for the telephone line). Also, watch out for metering charges. SDSL is a commercial grade service. Below are a list of providers who are offering the service in Austin. Although you may purchase 160 Kbps connections for as little as $103 per month from verio.net, I have listed the 1.5 Megabit per second connection speed, the highest connection speed, as a basis for comparison (November, 1999).
SDSL Order Fullfillment So, the order has been placed for SDSL, what can I expect? You can expect a 45-day installation period. Here is the process: (1) Your ISP will contact your CLEC, your Competitive Local Exchange Carrier (i.e., NorthPoint, for example), with your order. (2) Your CLEC will contact your local telco to request a circuit. (3) Your telco (i.e., Southwestern Bell) will install your SDSL circuit and test it--you may not know that this step has been completed. (4) Your CLEC will make an appointment with you to do your inside wiring. If you have ordered a router through your ISP, they will also deliver the router at this time. (5) Either your CLEC will provide you with your IP addresses or you will contact your ISP, and they provide you with your IP addresses. At this point, your CLEC and/or ISP will help you configure your systems and get connected.
General DSL Links North Point's Broadband Traveler's Guide (PDF) Links for ISPs
General Links
Data Speeds Continue to Climb
With the spread of DSL, cable modems and other digital connections, before too long, the average data connection will be high-speed 1 Mbps connection. TeleChoice just completed a survey of xDSL deployment (November 1999), and they came up with the following projections. Figures represent U.S. DSL lines in service. HDSL is not included.
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