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BTw IP Profile / bRAS Profile

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This page contains information and FAQs about BT's IP Profile.

BT IP Profile


~ What is an IP profile?

Your IP profile is closely related to the BTw bRAS profile and is an indication of the maximum throughput speed your line can attain whilst that particular profile is in place.

According to BTw, the first Data Rate should be set within 75 mins of going live on maxDSL.
Most customers will find that their line has a profile set at the bRAS within 3 days, although it can take up to 10 days for some lines to fully stabilise.

For Users on a 20CN product, the IP / bRAS profile is based on your lowest sync speed, and jumps up in 0.5Mb or 0.25 Mb stages.
So although you may get higher sync speed, your bRAS profile will limit you to what throughput speed you are likely to achieve.

For users on a 21CN exchange, the IP profile is calculated as 88.2% of your sync speed.
For FTTC/VDSL2 which uses PTM, it is around 96.8% of your sync speed.

Only BT Wholesale products have bRAS and IP Profiles, if you are with an LLU ISP then you wont have a bRAS or IP profile.

  bRAS IP profile top

~ How is my IP profile monitored?

Each time you sync, the DSLAM's Management Device will process this information and send it to the Rate Adaptive Profile (RAP) function which is one of the duties performed by RAMBO.
RAMBO then sends this information to the bRAS where the profile is applied.
Rate Adaptive Process
click for full image

More information about the bRAS control and the RAP function can be found on the DLM system page.

Note: Sometimes very quick resyncs are not always detected by the Rate Adaptive Process and it is recommended to leave 1 minute between a power down and resync.

  bRAS IP profile top

~ Why do we need an IP / bRAS profile?

The simple answer is to stop traffic bottle-necking at the exchange backhaul VPs. A maximum throughput level is needed to stop more data than your line can physically achieve being sent down the backhaul and causing packets to be dropped at the DSLAM.

When we request data this will firstly comes down over high speed UK backbone (Colossus) to the RAS.
From the RAS traffic will traverse the ATM backhaul where it branches off to the different exchanges. These Virtual Paths on some exchanges can be relatively small (say 20-50 MB). If you have a lot of users at the same exchange requesting data coming off the backbone fast, this could soon swamp the VPs. Therefore BT's solution is to throttle the speed of "our" data at the RAS and not allowing data to travel down the VP at a speed any faster than our connection can handle.

The IP profile is a "net" figure after an allowance has been made for any processing overheads such as TCP/IP and ATM overheads.

  bRAS IP profile top

~ How can I find out what my IP Profile is?

You can find out what your IP profile is currently set at by performing a Broadband Performance Test.

IP profile result

In addition your ISP should also be able to find out this information from data provided to them from BT called an Actuate Report.  Be aware though that not all ISP Help desks will know what this is, and it isn't always information that CS support staff - particularly on some of the larger ISPs - are able to see. bras profile

  bRAS IP profile top

~ How is my IP Profile calculated?

It is based on your lowest sync speed over a period of time, and makes an allowance for TCP/ATM overheads. BT uses a range of figures based on the figure which you sync to the exchange at.

BTw is using 3 different methods to calculate your IP profile depending on how your broadband is provisioned. ie if your exchange is 20CN or 21CN or if its FTTC.  The reasons for different profile calculations is likely to be due to the more recent products using PTM which has less overheads than ATM.

  • For FTTC / VDSL / Fibre / Infinity

    From observations, BT would appear to be using approx 96.8% of the sync speed to calculate the IP profile for FTTx products.
  • For 21CN WBC & adsl2+ Products

    With effect from late 2011, BT introduced a new Quantisation DLM system that results in much quicker updating of the IP profile - which is calculated as 88.2% of the sync speed.

  • For 20CN (MaxDSL) Products

    The 'up to 8Mb' products on 20CN exchanges has set parameter bands based upon your sync speed.  The full table is listed further down or you can use this quick calculator.
Calculate IP Profile (20CN)
Enter Sync Speed:  
IP Profile:  
Maximum Throughput Speed: 
Range From:  
Next Step up: 

     bRAS IP profile top

~ How often does it change?

Previously your IP profile would be amended within 75 mins for a decrease in sync speed, or after 3 days for an increase in sync speed. Obviously this arrangement wasn't always the best solution since it could take several days to recover from one bad sync period such as during a thunderstorm.

With effect from Aug 2007, BT will introduce "Adaptive Max Logic" which will replace both the 3 day system and Blip logic. This should be of benefit to those who have suffered from an unusually low sync, although smaller increases will take a bit longer.

Your IP profile will continually change whilst you are on a maxdsl service dependant upon the speed at which you connect to the exchange at. Good Lines will seldom see any changes, but long lines are subject to frequent changes depending upon the connection speed. Because of the way SNR behaves, most lines will achieve a better sync speed during the early part of the day than in the evenings.

Users on a 21CN exchange or FTTC, where DSLAMs use the quantisation system, should see changes occur much quicker.

  bRAS IP profile top

~ WBC Banded Profiles

WBC Banded Profiles apply to adsl lines on BTs 21CN network such as adsl2+. 

Banded profiles may be applied to lines that have difficulty maintaining sync at the higher speeds.

The theory is to stop lines initially syncing too high at a speed which cannot be sustained and would normally encounter frequent disconnections and slow throughput speeds due to a high number of errors on the line which causes data to be retransmitted.

The list on the right shows the available banded profiles which may be applied by the DLM.

Banded Profiles
160 288
288 576
576 1152
1152 2272
1472 3072
2272 4544
3328 6656
4864 9728
7168 14336

  bRAS IP profile top

~ What is "Adaptive Max Logic"?

This applies to adslMax - ie the 'up to 8Mb' product available on 20CN exchanges.

  • Decreases in sync speed will still reflect in the IP profile within 75 mins.
  • Increases in sync speed will depend on the percentage of the increase and will vary between a few hours and up to 5 days.

A large % increase in sync speed should see the IP profile rise within 4-6 hours, whilst a small increase may take up to 5 days before the IP profile reflects the change. BT estimates that under "Adaptive Max Logic" more than 60% of increases will now occur before they would on the old 3 day system.


1. - Large increase - Line dropped to a 576 sync during a thunderstorm (profile = 500), after a resync it went back up to 7616 (profile 6500). Profile increase = 6000/500 *100 = 1200% increase which should occur in 4-6 hours.
2. - Small increase - Sync increase from 7616 (profile 6500) to 8128 (profile 7150) after interleaving removed. Profile increase = 650/6500*100 = 10% which may not take effect for 5 days.

How long it exactly takes for increases to be applied would also seem to depend on how busy the system is.

  bRAS IP profile top

 ~ How long will it take for an increase to occur on 20CN products?

The figures below give a rough indication of how long changes are scheduled to occur after an increase in the IP profile. The Percentage Increase in IP Headline Rate = Period before the BRAS profile changes begin.

4 hours
12 hours
24 hours
48 hours
72 hours
96 hours
120 hours

Remember that some ISPs need to increase their own systems accordingly in line with BT's, which may take a little longer to process.

~ My (20CN) IP profile is "x" so what speed must I have synced at?

Whilst I cant tell you the exact figure - it is possible to calculate which range of figures your lowest sync speed will have been in.

Show IP profile range (20CN)
Enter IP Profile:  
Sync Range        
Next Step up:

  bRAS IP profile top

 ~ FTTC IP Profile

Unlike ADSL which uses ATM framing (PPPoA), VDSL2 uses PTM framing (PPPoE). The biggest advantage is that PTM has substantially less overheads than ATM and more efficient throughput.
Because VDSL uses PTM framing, the allowance for overheads is much less than on 21CN products and is usually in the region of 3.2%.  This figure may vary ever so slighly depending upon framing parameters set by the DSLAM.

~ Full list of available IP & bRAS profiles used by BT Wholesale & BT Openreach.

Calculated as 96.79% of the sync speed or 96.69% for g.inp lines.
To get your sync speed from your IPprofile: Sync = IPprofile / .9679
21CN ADSL2/ADSL2+ and 21CN WBC adsl1
Calculated as 88.2% of the sync speed.
20 CN adsl1
Sync speed (incr 32kb stages) IP profile bRAS ATM bit rate profile Maximum Throughput speed
(AAL5 Payload)
From To
160 kbps 256 kbps 135 138 Up to 135 kbps
288 kbps 384 kbps 250 256 Up to 0.25 Mbps
416 kbps 544 kbps 350 370 Up to 0.35 Mbps
576 kbps 832 kbps 500 512 Up to 0.5 Mbps
864 kbps 1120 kbps 750 768 Up to 0.75 Mbps
1152 kbps 1408 kbps 1000 1024 Up to 1 Mbps
1440 kbps 1696 kbps 1250 1280 Up to1.25 Mbps
1728 kbps 1984 kbps 1500 1536 Up to 1.5 Mbps
2016 kbps 2240 kbps 1750 1792 Up to 1.75 Mbps
2272 kbps 2816 kbps 2000 2048 Up to 2 Mbps
2848 kbps 3392 kbps 2500 2560 Up to 2.5 Mbps
3424 kbps 3968 kbps 3000 3072 Up to 3 Mbps
4000 kbps 4512 kbps 3500 3584 Up to 3.5 Mbps
4544 kbps 5088 kbps 4000 4096 Up to 4 Mbps
5120 kbps 5664 kbps 4500 4608 Up to 4.5 Mbps
5696 kbps 6208 kbps 5000 5120 Up to 5 Mbps
6240 kbps 6784 kbps 5500 5632 Up to 5.5 Mbps
6816 kbps 7360 kbps 6000 6144 Up to 6 Mbps
7392 kbps 7936 kbps 6500 6656 Up to 6.5 Mbps
7968 kbps 8096 kbps 7000 7168 Up to 7 Mbps
8128 kbps 9087 kbps 7150 7320 Up to 7.15 Mbps
old WBC ADSL 2+ Profiles
9088 kbps 10207 kbps 8000 8192 Up to 8 Mbps
10208 kbps 11359 kbps 9000 9216 Up to 9 Mbps
11360 kbps 12479 kbps 10000 10240 Up to 10 Mbps
12480 kbps 13631 kbps 11000 11264 Up to 11 Mbps
13632 kbps 14751 kbps 12000 12288 Up to 12 Mbps
14752 kbps 15903 kbps 13000 13312 Up to 13 Mbps
15904 kbps 17023 kbps 14000 14336 Up to 14 Mbps
17024 kbps 18175 kbps 15000 15360 Up to 15 Mbps
18176 kbps 19295 kbps 16000 16384 Up to 16 Mbps
19296 kbps 20415 kbps 17000 17408 Up to 17 Mbps
20416 kbps 21567 kbps 18000 18432 Up to 18 Mbps
21568 kbps 22687 kbps 19000 19456 Up to 19 Mbps
22688 kbps 23839 kbps 20000 20480 Up to 20 Mbps
23840 kbps - 21000 21504 Up to 21 Mbps

  bRAS IP profile top

~ "Stuck bRAS profile"

Although not quite so common these days as when dslMAX was first introduced, there is still the odd occasion when a line seems to get what is known as a stuck bRAS profile.

When your line is first profiled the theory is that the DLM system should set your IP profile in line with your sync speed within the first 75 mins. If a profile is not correctly set then the default value of 2048/2000 is used. This may clear within 3 days and it may help if you say leave your router switched off overnight... but some lines just seem to get "stuck".

From my own observations this mostly appears to happen on the better quality lines - ie ones that don't loose sync or need any automatic DLM configurations.

If you suspect a stuck bRAS on your line then you will have to contact your ISP asking them to get BTw to clear a stuck bRAS profile fault.

  bRAS IP profile top

~ How does DSL Max work?

For more information on how Max DSL works and how its different from traditional adsl - see How DSL Max works and What is MaxDSL? . In particular look at the DLM process to see how it is responsible for the bRAS and IP profile.

  bRAS IP profile top



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