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Incorrect IP Profile?

SteveZ
Hooked
Posts: 7
Registered: ‎17-12-2018

Incorrect IP Profile?

Hi

My router sync speed to the cabinet is currently 67.1 Mbps. My BT IP profile is 58.6 Mbps. My download speed on a wired connection is usually around 55 Mbps - give or take 3 Mbps.

For some considerable time now - in fact since I've been on Plusnet Fibre Extra over a year ago - my BT IP profile has always been around 8 - 10 Mbps lower than my router sync speed. (Sometimes my router syncs at just over 70 Mbps.)

From what I have read, the IP profile should be around 97% of the router sync speed, so I assume the IP profile should currently be around 65 Mbps.

I've spoken to Plusnet Technical Support guys on the phone a few times and they arranged for BT to test the line which tested good to the cabinet (only around 470 metres away). BT have tested the line a number of times now and claim it is perfect.

When I asked Plusnet Technical Support on the phone why the IP profile was consistently so much lower than my router sync speed, they have no explanation for this. As far as they were concerned I was on a 80/20 Mbps service and not restricted in any way.

Further info:

I have tried various routers and the sync speed is very similar with all of them, yet the IP profile is always 8 -10 Mbps lower, so it's not a misreporting of the sync speed by the router.

My router is connected directly to the incoming BT cable with what I understand is the latest NTE5C master socket.

Even when the router left completely alone for a number of weeks without any restarts/power downs, the IP profile never seems to change very much, always staying the biggest part of 10 Mbps below the router sync speed.

Any ideas?

Thanks

Steve

8 REPLIES 8
Baldrick1
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Re: Incorrect IP Profile?


@SteveZ wrote:

From what I have read, the IP profile should be around 97% of the router sync speed, 


My understanding is that if G-INP on your line is set to Retansmission High the profile should be 91-92% of your sync speed. This might explain most of the disparity. 

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RealAleMadrid
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Re: Incorrect IP Profile?

@SteveZ I have seen posts on this forum where GEA tests have shown that on Retransmission high the profiling system uses an incorrect reduced value for the sync speed and sets the profile at about 87% of the true sync speed. There has been a lot of discussion on this this but Plusnet have never come up with any sensible explanation.☹️ 

It is possible, if you are lucky, to get DLM to switch to retx low which I have done by temporarily capping sync speeds at a reduced level but that requires CLI commands on a Broadcom based modem such as an unlocked Huawei HG612.

SteveZ
Hooked
Posts: 7
Registered: ‎17-12-2018

Re: Incorrect IP Profile?

Thanks Baldrick1 for replying.

How would I know if my line was set to 'Retransmission High' - and if it is, why is it if the line has been tested as 'good' several times by the BT Engineers?

I was under the assumption (possibly wrongly), that between the cabinet and my router the line is tested by Digital Line Management and a suitable sync speed is then established based on line conditions, then the IP profile is set (by who - BT?) to a little under the sync speed.

Any idea what the requirement is for 'Retransmission High' on a good line? I would have guessed that any problem with the line would simply reduce the sync speed.

SteveZ
Hooked
Posts: 7
Registered: ‎17-12-2018

Re: Incorrect IP Profile?

Thanks RealAleMadrid. You'd have thought that - if Retransmission High is the problem - that this would be something that Plusnet could sort out - or arrange to be sorted out.

The router I'm using at the moment is a Billion 8800NL which I believe uses a Broadcom chip. I'm unsure if it's unlocked or not though.

Baldrick1
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Re: Incorrect IP Profile?

@SteveZ 

I don't think that Retransmission High is an indication that there is anything wrong with your connection. I believe that this gets set if you have a good connection but are a distance from the cabinet and the DLM reduces your SNR to 3dB to extract the best performance possible from your line.

.

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SteveZ
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Registered: ‎17-12-2018

Re: Incorrect IP Profile?

@Baldrick1 

As I mentioned earlier, the cable length from my router to the cabinet is 'only' around 470 metres.

I'm not sure if that's classed as "a distance" in terms of fibre broadband? I thought that it was relatively close - the Plusnet Technical Support guys on the phone seemed to think so... but then again, they didn't appear to know what the cause low IP profile could be!

Baldrick1
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Re: Incorrect IP Profile?

@SteveZ 

If you are very close to the fibre cabinet then you can easily get the full 80/20 service with a high SNR. As you move away from the cabinet the speed drops off and the DLM drops the SNR to try to maintain 80/20. You get to the distance where the SNR gets down to what is effectively the DLM end stop of 3dB. After this the 80/20 speed can no longer be maintained and the speed drops. If you do a Google search you will find speed v distance charts.

A GEA test might give a bit more insight into how well the line is performing.

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SteveZ
Hooked
Posts: 7
Registered: ‎17-12-2018

Re: Incorrect IP Profile?

@Baldrick1 

 

GEA - Generic Ethernet Access - had to look that one up!

I have in the past looked at distance charts for FTTC and syncing at 65 - 70 Mbps is pretty decent for 470 metres from the cabinet.

The fact that the relatively short line consistently tests as good, then you would have thought that Plusnet would be able to diagnose the problem and give a definitive answer as to why my IP profile is the biggest part of 10 Mbps lower than my sync speed, rather than just booking BT out again and again to retest the line. Ideally Plusnet would then go on the fix  the issue - if at all possible.

Oh well, I'll reassess the situation at contract renewal time.