ADSL
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What is ADSL MAX?
What speed should i expect?
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How do i diagnose a speed problem?
Top Faults & troubleshooting them
How do i do a speed test on BT's network?
Installing an ADSL Router
Installing an ADSL Modem
Check if a user is online
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What speed am I likely to achieve with Link Connect ADSL Products?Aim of this articleThis article lays out some guidelines for what download speed you are likely to achieve on a Easy, Biz or a Network product. Using this information you can assess whether your data speed is normal, or whether there could be a problem. What is the maximum speed that I can get with Link Connect Products?All NON-fixed rate products will attempt to sync at a maximum line rate of 8128 kbits/s. Accounting for ATM overheads this translates to a maximum achievable data rate of 7150 kbits/s (or 893.75 kBytes/s) What are the reasons why I might not achieve this speed? There are a number of technical reasons why you may not achieve this speed, which are explained in detail later in this article. These reasons are listed below: * Physical line limitation * BRAS profile limit. * Virtual Path Congestion. How does the physical line limit affect me?ADSL uses your copper telephone line to carry a signal between the ADSL modem at your premises and equipment at the BT telephone exchange. As the noise level increases there becomes less and less spectrum available to use for the ADSL signal, and hence the sync speed is reduced to fit into the available margin. The noise (or attenuation) level on your line will be directly proportional to the line length .It may also increase if your line is of a poor quality. BT's Dynamic Line Management systems will automatically negotiate a sync speed which gives the best possible performance your line is able to achieve. This will be a maximum of 8128 kbits/sec, but can vary significantly depending on your line quality. You can usually check what line sync speed has been negotiated by looking at the line statistics information on your router or modem status page. The quality of the line between your premises and the exchange is fixed, but you may be able to make improvements to the internal telephone wiring within your property. * We would advise using good quality filters. Avoid the filters that look like telephone doublers. The filters that look like small rectangular boxes with a short cable to the telephone socket are generally better. Check that none of your filters are faulty by swapping them out and checking your line statistics. * Minimise the amount of extension wiring in use. If it is possible to locate your router at the BT master socket for your premises then this may yield improved stability and performance. * Ensure all your telephony equipment is properly filtered. How does the BRAS profile limit affect me?BT's line management systems will limit the speed you can download data across your ADSL line in relation to your line sync speed. Log on to your router or modem and check what speed it is synchronised at, and then use the table below to check what your BRAS profile limit should be.
Any changes to your Line sync rate should be reflected in the BRAS profile within 75 minutes, but in some cases (especially where the line sync rate has increased) this may take up to 3 days to update. NOTE: It is currently not possible for Technical Support to check what BRAS profile your line is set to. The best way of determining this is to perform several BT speed tests at off peak times (including late at night or early in the morning) What is Virtual Path Congestion?ADSL is a contended product, using shared bandwidth within BT's Network. This means that your bandwidth is shared with other ADSL users at the same telephone exchange. BT state that because of congestion on these Virtual paths you are unlikely to achieve the full theoretical limit for your line at most times of the day. At peak times of the day they state that it may well perform similarly to a Home/Office 2000 line. The highest/lowest data rates that fall within the product specification details of the ADSL performance thresholds provided on services based on BT's IPStream Home, IPStream Office, IPStream Max and IPStream Premium services. These thresholds are as published by BT in relation to these services. What are performance thresholds?:The performance thresholds have been defined to help customers understand what level of service to expect from the various services. They define minimum and maximum performance levels in normal circumstances. Max services are not contended but are subject to usage restriction's & if the usage for your product is exceeded you will be charged £0.95p+VAT PER GB IPStream Max: IPStream Max is used to provide Easy 8/4 2GB, Biz 8/4 10,30,90GB. The performance thresholds are as follows:
IPStream Max Premium: IPStream Max Premium is used to provide Network 8/8 50GB and Network 8/8 100GB. The performance thresholds are as follows:
Data rates which vary during the day, but never fall outside the acceptable thresholds published above are very likely to be the result of congestion on your contended virtual path. In order to raise a speed fault you should log several BT speed tests demonstrating the poor speed, separated by at least 4 hours, and then contact support. Details of how to perform a BT speed test are in the speed tester HowTo |
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