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RADSL / Max ADSL / up to 8Mbps FAQ

Can I get RADSL on the business services?

Products aimed at businesses also use rate adaption, with Office 500 and Max Premium both being available to businesses. It should be noted that while a Wholesale product may be called an Office product, some providers will allow a consumer to order it, this is particularly to allow people to benefit from the higher upstream option on the Max Premium service.

I've heard the hardware will be different?

RADSL (Rate Adaptive DSL) does not affect your choice of hardware. With the launch of Max products in 2006, people may find that ADSL modems/routers that connect via Ethernet or wireless may perform better than their USB counterparts.

If you find your ADSL modem is not very stable with a rate adaptive product, changing to hardware from a different manufacturer is worth trying. Some research to determine whether the innards are different is worthwhile, ideally you are looking for hardware that uses a different ADSL chipset.

How will I know how fast I can get from an up to 8Mbps or ADSL2+ product?

It is possible to estimate how fast you may get on a Max, Max Premium or LLU product for the downstream line speeds. The BT Wholesale line checker at www.btwholesale.com/getbroadband will give an estimate based on a previous measurement of the capacitance of the line.

If you already have an ADSL service, you may have access to your line attenuation and noise margin (SNR Margin) figures, which can be used to provide an estimate of the maximum line speed, which may be more accurate than a simple line length guess. Two main sites exist for this form of calculation Mr Saffron's ADSL/ADSL2+ calculator, and www.dslzoneuk.net. It should be said that the estimator's generally give a best case figure, for the line to be stable it may need to run at lower speeds.

If you have no idea about how to get your attenuation and noise margin figures, take a look at www.kitz.co.uk/adsl/frogstats.htm which shows how to obtain the stats from the most common hardware. This was written by one of our forum users.

My line test failed ADSL install, will it work with Rate Adaptive ADSL?

The answer to this question depends greatly on when you applied for your ADSL service. If before September 2004 to be allowed a fixed speed 0.5Mbps service you had to have a line shorter than 6km (less than 60dB attenuation).

The launch of the Max (Rate Adaptive) products from BT Wholesale made a small difference to those on very long lines, and if a previous order failed and the online checkers will allow you to order an ADSL service it is worth trying a MAX product as this may work since it will connect at 160Kbps and upwards. WARNING Some broadband providers refuse MAX orders on lines which may be slower than 1Mbps, this is a provider specific filter rather than a BT Wholesale issue.

How fast is RADSL?

This depends both on what service you ordered, and the capabilities of your telephone line. If you ordered a 0.25Mbps or 0.5Mbps service, the downstream line speed is fixed, but if you ordered a Max product your downstream line speed may be anything between 160Kbps and 8Mbps.

How does RADSL work?

When connecting, the ADSL modem splits the upstream and downstream sections of the spectrum into discrete sections known as bins, and will try to use as many as possible. The modem will assign a number of bits to each bin, and a noisy bin will carry less bits than others. This allows the modem to cope with specific frequencies that AM radio stations produce interference on.

The upstream section has less bins than the downstream. ADSL2+ has the potential to use double the number of downstream bins compared to ADSL and ADSL2. ADSL2 manages its better performance by how it populates the bins with data and error correction techniques.

Should I be using RADSL?

If you have ordered, or are using any product based upon BT Wholesale IPStream 500 (USB), IPStream S500 (Ethernet) or Home/Office 500 (wires only), you will be using RADSL automatically. The Home/Office 1000/2000 products use fixed line speeds.

If you applied for ADSL before July/August 2001 and failed due to poor line quality, or you live too far from your local exchange (greater than 3 to 4km), the new more tolerant RADSL limits will give you a second chance to obtain broadband internet access at your premises. You need to go ahead and re-order ADSL. The new RADSL (rate-adaptive) test limits will be automatically used by BT.

After 31st March 2006, two new products are available from BT Wholesale, Max and Max Premium. These products use rate adaption for both the downstream and upstream speeds. The downstream line speeds will range between 8Mbps and 288kbps, and upstream between 448kbps and 288kbps. The Premium service supports a maximum upstream of 832kbps. Since the Max products are fully rate adaptive there are no specific limits, you will get whatever speed your line is capable of.

What does RADSL stand for?

RADSL stands for Rate Adaptive Digital Subscriber Line. Rate adaption can be applied independently to the upstream and downstream sides of an ADSL connection.

I have Max ADSL, but what download speeds should I be getting?

The download speeds from a Max ADSL service are determined by the line sync speed (connection speed shown by your ADSL modem). A simple rule applies, if your line sync speed drops to a lower value the download speeds will adjust immediately, but download speeds will only rise if the line sync speed remains stable for between 75 minutes and five days. Larger changes in sync will mean it is more likely the maximum possible speed will increase the same day.

For example, if you connect at 1248Kbps normally, your downloads should be close to 1Mbps, but if you suddenly reconnect at 576Kbps the maximum download speed will drop to 500Kbps. Then if your ADSL modem reconnects again later that day at 1152Kbps the speed wont improve for a variable period of between 75 minutes and five days, and will only improve if everytime the modem reconnects you reconnect at 1152Kbps or higher.

A table showing the line sync speed and the corresponding IP profile (sometimes called BRAS Data Rate) is shown below. Some service provider portals will tell you your current IP Profile setting, alternately visit www.speedtester.bt.com and this will test the download speed and also give you your current IP profile value. A warning about the tester site, it does not always work if lots of other people are using it.

Line sync speed (connection speed)

IP Profile / BRAS Data Rate

from 288Kbps (Kilo bits per second) 0.25Mbps (Mega bits per second)
from 416Kbps 0.35Mbps
from 576Kbps 0.5Mbps
from 864Kbps 0.75Mbps
from 1152Kbps 1Mbps
from 1440Kbps 1.25Mbps
from 1728Kbps 1.5Mbps
from 2016Kbps 1.75Mbps
from 2272Kbps 2Mbps
from 2848Kbps 2.5Mbps
from 3424Kbps 3Mbps
from 4000Kbps 3.5Mbps
from 4544Kbps 4Mbps
from 5120Kbps 4.5Mbps
from 5696Kbps 5Mbps
from 6240Kbps 5.5Mbps
from 6816Kbps 6Mbps
from 7392Kbps 6.5Mbps
from 7968Kbps 7Mbps
8128Kbps 7.15Mbps

What are the myths behind the BT Wholesale Max product?

A great many myths and legends have grown up around the rate adaptive product that is IPStream Max and DataStream Max in the UK. To help people understand some of the truth behind all this BT Wholesale has published a document that can be downloaded in PDF format from here.

As of November 2007, a new version of the document is in product and some specifics like how the BRAS Data Rate (IP Profile) is adjusted will have changed.

What is the IP Profile?

Firstly let’s be clear this only applies to people who have an IPStream/Datastream Max or Premium Max product. The way to tell is to look at what speed the upstream side of your ADSL modem is connecting at, on Max this is usually 448Kbps and on Max Premium 832Kbps. There are some exceptions to this since the upstream is rate adaptive and on poorly performing lines may connect at another value, but for most people those two upstream speeds indicate a BT Wholesale Max based service.

The IP Profile is a setting that is derived from your downstream connection speed and is used by BT Wholesale to manage the amount of backhaul capacity needed on their network for the millions of people with Max connections. If you have a 7Mbps IP Profile it is impossible for your connection to download stuff from the internet at faster than 7Mbps (~7000Kilo bits per second, 875KB/sec). There are a limited number of IP profiles possible, twenty in actual fact and they can be seen in full at this FAQ entry.

The large difference between connect speed and IP Profile is down in part to the fact that the data is carried over the BT Wholesale network using ATM packets, thus there is a an overhead for carrying IP (Internet Protocol) traffic of around 10 to 13%. The exact figure varies according to the data being transferred and configuration of the IP stack on the computer. So even without the IP Profile the maximum speed possible from a sync speed of 8128Kbps is around 7250Kbps, the next lowest IP Profile is 7150, so 100Kbps of traffic is wasted.

Why is my IP Profile a lot lower than my downstream connection speed?

If you for example have a connection speed of 4032Kbps and an IP Profile of just 0.75Mbps, this suggests that at some point within the last five days your modem reconnected to the exchange at a connection speed between 864Kbps and 1151Kbps. The IP Profile will improve given time and prior to August 2007 this was on a fixed 3 day wait period before it improved. As of August 2007 a more flexible system has been implemented where large improvements in the IP Profile may take place with 75 minutes, for example a jump from 135Kbps up to 7.15Mbps should happen quickly, whereas a small increment from 3.5Mbps to 4Mbps may take the full 5 days the current system allows.

The reason why the changes take a length of time is to avoid millions upon millions of database updates each day, which will impact on BT Wholesales ability to manage the network.

It should be remembered that the IP Profile will lower immediately (within a minute or so) if your downstream connection speed changes and takes into the range for a different IP Profile.

Can I make the IP Profile change faster?

Some people advise using tricks to make your modem sync very slow and then quickly let it sync faster again, the problem with this is that if you get it wrong you could end up on an even lower IP Profile than you started with.

Why can't the IP Profile be set to a higher value than my downstream connection speed?

This is not desirable because if this was done the BT Wholesale network would try to feed you data faster than your ADSL line would manage, this data would be then buffered and after a short while packets may be thrown away (dropped), resulting in lost data and having to request data again. Another effect of this is that it makes the network hardware busier and may impact on how well the network can handle all the data from other people.

How can I find out what my IP Profile is?

A number of broadband providers expose the setting on their customer portal as the BRAS Data Rate or IP Profile. So you can login and see what the current value is and how it has changed. Broadband providers get informed of each change to the IP Profile so in theory if a provider stores this information it should be available to help desk staff. NOTE: In some providers only second line support may have the ability to see the information.

For those that cannot get the IP Profile from their ISP see this FAQ entry for information on the using the BT Wholesale Speedtester.

I think my IP Profile is stuck, what can I do?

Remember that it takes up to five days of being connected at a downstream connection speed that justifies an increased IP Profile now, so don't assume it is stuck until the five days is up. Make sure your ADSL modem has not reconnected at a slower speed when you were not watching, some modems log all the connection attempts making it easier to check this.

If after five days it is still stuck, raise this issue with your broadband provider, if this does not progress then try emailing andrew@thinkbroadband.com who may be able to help.

I have always connected at 8128Kbps, but never see downloads faster than 2Mbps?

There is a situation where a line that is very stable when it gets converted to MAX does not trigger an update to the IP Profile. If you have been like this for more than ten days and the broadband provider has failed to resolve it then email andrew@thinkbroadband.com who may be able to help.

Remember to check what speeds you get at off peak times such as around breakfast time, to ensure it is not congestion on the BT Wholesale network, broadband provider or just the internet in general.

I've heard removing the ring wire can improve my connection, how do I do this?

The ring wire (sometimes called bell wire) is a hang-over from old telephones that needed the telephone line to generate the bell ringing signal on a third wire. Modern telephones generally do not need this third wire, and its presence creates an imbalance in the telephone wiring and can cause rate adaptive ADSL connections to connect slower than would otherwise be expected.

If you have already fitted an NTE5 ADSL faceplate then removing the ring wire will not make any difference. It should be noted that any improvements will be immediately apparent if you look at the connection speeds reported by your ADSL modem after it has restarted. Actual download speeds on a Max product will take some time to improve due to the delay in the IP Profile improving which is between 75 minutes and five days.


Click image for larger version

The image above shows a standard BT Master Socket with the removable faceplate lifted off. There are four wires connected; the blue pair to pins two and five, and the orange pair to pins three and four. The ring wire is the wire on pin three, i.e. orange wire with a white strip. It should be pointed out that old wiring may use just four solid colours and the wires will not be twisted together, in which case rewiring the telephone extensions in the property to use modern twisted pair phone cables is worthwhile; www.adslnation.com stocks suitable cable. If you have two or more telephone extensions, you will find multiple wires connected to pin three.

To disconnect the ring wire(s) lift the wire away from the metal conductor as shown below:


Click image for larger version

Removing the wire on pin 3 on the other sockets around your property may help, but generally will have no effect. As with any changes make sure your telephones and ADSL still work and if not return your wiring to its previous state, to test the phones fully you need to make an incoming call to check they still ring.

NOTES:Where possible do not cut the ring wires, but lift them out of the connector, cutting them may leave you with too short a wire to reconnect when you move out of the property. If refitting a wire to connectors like those in the sockets, an IDC Krone tool must be used which can be purchased at stores that sell telephone extension kits (such as DIY stores) and also online.

This procedure of removing the ring wire is also useful if you do not have an identifiable master socket in the property.