With TalkTalk Wholesale ADSL circuits we (and customers) have full control over the line profile. By default we disable DLM, and are able to set the profile manually.

On the control pages for the Line we have the profiles selection:

To change the profile, select the one you like, and then press Profile to make the change. It will just take a few seconds to apply, and the line will resync.

Why change profiles?

On the positive side, changing the profile can:

Increase throughput speed
Improve reliability
Help with errors (packetloss) caused by interference

The reverse of these is also true, if your line cannot support a profile selected.

Notes

The fastpath (non-interleaved) profiles are more likely to drop on a noise burst than the interleaved profiles

How long does a profile change take?

Not long! The profile change is set through to TalkTalk Wholesale as soon as you click the button on the control page, and the line will resync within a minute. If the profile change failed, then the log will say failed, it it was successful then it will say Done:

Understanding the Profile Names

We have a table of all the available profiles, See here

Annex A Line Profiles

Annex A line profiles are of the form:

XYYY_SNR_DDD_UUU_Protocol

Where:

X denotes the adaptive setting:
- If this is S then the profile is dynamic
- If this F then the profile is fixed.
YYY denotes the Interleaving settings:
- F indicates that interleaving hasn’t been applied and that this is a fast profile.
- I followed by a number indicates the size of the interleaving delay. The greater the number the greater the interleaving applied.
SNR denotes the target Signal to Noise Margin.
- Where this is a single number, this number indicates the target for both upstream and downstream
- Where there are two, the first indicates downstream and the second indicates upstream.
- The lower the number the greater the achievable line rate, the higher the number the higher the number then the lower the achievable line rate.
- Note: Some fixed profiles omit the SNR property from their name, where this is the case their target margin is 6dB.
DDD indicates the maximum download speed.
UUU indicates the maximum upload speed.
Protocol indicates if the profile is tied to a specific ADSL protocol. Where this is negated, the profile will negotiate with the CPE starting at ADSL2+ and working down to G.DMT.

Annex M line profiles

Annex M line profiles are of the form:

MXYYY_SNR_DDD_UUU:MInpN

Where:

M denotes that this is an Annex M profile.
X denotes the adaption setting.
- (S) Dynamic: This is where a maximum downstream speed is set but the line may not support that speed so the highest supportable speed is negotiated.
- (F) Static: This is where a maximum downstream speed is set and the line will be fixed at that specified speed.
YYY denotes the Interleaving setting:
- F indicates that interleaving hasn’t been applied and that this is a fast profile.
- I followed by a number indicates the size of the interleaving delay. The greater the number the greater the interleaving applied.
SNR denotes the Target Margin. Where this is a single number, this number indicates the target for upstream and downstream, where there are two, the first indicates downstream and the second indicates upstream Note: Some fixed profiles omit the SNR property from their name, where this is the case their target margin is 6db.
DDD indicates the maximum download speed.
UUU indicates the maximum upload speed.
MInpN denotes the Impulse Noise Protection values. Where this is set to 0 there is in none, else the values are that for Downstream followed by upstream, H denotes 1⁄2 a tone.

Diagnostic Profiles

There are a few diagnostic profiles that can be used to isolate faults.

View the Profile list

We have a table of all the available profiles, See here

Profile Factors

SNR

SNR is a measure of signal strength and as such is measured in Decibels (dB). The values in use on the TTT network are:

6dB
9dB
12dB
15dB

3dB should be available by 2014. Customers could try configuring their modem to force a 3dB profile, but this is not officially supported.

Interleaving, Error Correction and Delay

Packets of data that are transferred across a DSL line are split down into smaller blocks of data; these are then sent sequentially sent across the DSL line. As they arrive at the receiving end, they reconstructed back into the original larger packets of data.

If one block of a larger packet is lost due to line interference, the packet can be recreated using the remaining blocks that were received; data blocks reserve some space for data which can salvage a partially damaged block. This is known as Error Correction. Interleaving can be used as a form more robust form of error correction.

The ‘Delay’ of the Interleaving is simply a measurement of the size of the interleaving buffers. The size is measured in Milliseconds (ms).

The buffer sizes available on the TalkTalk network are:

Off (Fast)
8ms
16ms

The fastpath (non-interleaved) profiles are more likely to drop on a noise burst than the interleaved profiles

Impulse Noise Protection

Impulse Noise Protection (INP) is an error correction feature of ADSL2+ which makes interleaving more affective. It does not increase delay but does add in more error correcting bits which results in a drop in line rate for less noisy lines. Because of the increased noise immunity however, a slow noisy line will be able to sync at a higher rate with this feature enabled.

Note: On some hardware, INP can result in a substantial drop in downstream speed and should only be used where a line is particularly noisy and only slow speeds are achievable.