Intermittent connection errors
Hi,
I currently have intermittent connection issues. I had this a while back and it never seemed to get fixed - then one day it seemed to pretty much stop. Now it seems to have started again though. 
As I had no luck with phone support I thought I'd try here. I've looked through other cases and seen people suggesting to upload the WAN logs here, so this is what I've put below. I notice what seems like some low SNR results (I'm not an expert, but I've seen people say below 10dB is very bad, I'm seeing as low as 6 (or even -2dB if that's possible?) around when I've had outages recently. Could this be the issue and if so what is the fix? WAN logs below for outages this evening. Thanks to anyone that will try to help me get to the bottom of this. Screenshots of the logs also attached as this seems the only way to show the time of the events too.
(7224548.180000) WAN operating mode is VDSL
(7224548.180000) Last WAN operating mode was VDSL
(7224546.540000) PPP IPCP Receive Configuration ACK
(7224546.540000) PPP IPCP Send Configuration Request
(7224546.530000) PPP IPCP Receive Configuration NAK
(7224546.530000) PPP IPCP Send Configuration ACK
(7224546.530000) PPP IPCP Receive Configuration Request
(7224546.490000) PPP IPCP Send Configuration Request
(7224545.060000) PPPoE is up - Down Rate=42446Kbps, Up Rate=18169Kbps; SNR Margin Down=9.9dB, Up=8.3dB
(7224545.050000) CHAP authentication successful
(7224544.740000) CHAP Receive Challenge
(7224544.740000) Starting CHAP authentication with peer
(7224544.730000) PPP LCP Receive Configuration ACK
(7224544.730000) PPP LCP Send Configuration Request
(7224544.720000) PPP LCP Receive Configuration Reject
(7224544.720000) PPP LCP Send Configuration ACK
(7224544.720000) PPP LCP Receive Configuration Request
(7224544.720000) PPP LCP Send Configuration Request
(7224493.670000) PTM over DSL is up
(7224456.630000) PTM over DSL is down after 19 minutes uptime
(7224456.630000) PPPoE is down after 18 minutes uptime [Waiting for Underlying Connection (WAN Ethernet 2 - Down)]
(7224453.440000) PPP LCP Send Termination Request [User request]
(7223319.250000) WAN operating mode is VDSL
(7223319.250000) Last WAN operating mode was VDSL
(7223317.300000) PPP IPCP Receive Configuration ACK
(7223317.290000) PPP IPCP Send Configuration Request
(7223317.280000) PPP IPCP Receive Configuration NAK
(7223317.280000) PPP IPCP Send Configuration ACK
(7223317.280000) PPP IPCP Receive Configuration Request
(7223317.220000) PPP IPCP Send Configuration Request
(7223315.480000) PPPoE is up - Down Rate=35015Kbps, Up Rate=18169Kbps; SNR Margin Down=10.9dB, Up=-2.1dB
(7223315.460000) CHAP authentication successful
(7223315.170000) CHAP Receive Challenge
(7223315.160000) Starting CHAP authentication with peer
(7223315.160000) PPP LCP Receive Configuration ACK
(7223315.160000) PPP LCP Send Configuration Request
(7223315.150000) PPP LCP Receive Configuration Reject
(7223315.150000) PPP LCP Send Configuration ACK
(7223315.150000) PPP LCP Receive Configuration Request
(7223315.150000) PPP LCP Send Configuration Request
(7223260.030000) PTM over DSL is up
(7223222.070000) PTM over DSL is down after 0 minutes uptime
(7223211.510000) PTM over DSL is up
(7223151.290000) PTM over DSL is down after 140 minutes uptime
(7223151.290000) PPPoE is down after 139 minutes uptime [Waiting for Underlying Connection (WAN Ethernet 2 - Down)]
(7223148.020000) PPP LCP Send Termination Request [User request]
(7214752.960000) WAN operating mode is VDSL
(7214752.950000) Last WAN operating mode was VDSL
(7214751.160000) PPP IPCP Receive Configuration ACK
(7214751.150000) PPP IPCP Send Configuration Request
(7214751.140000) PPP IPCP Receive Configuration NAK
(7214751.140000) PPP IPCP Send Configuration ACK
(7214751.140000) PPP IPCP Receive Configuration Request
(7214751.090000) PPP IPCP Send Configuration Request
(7214749.520000) PPPoE is up - Down Rate=39120Kbps, Up Rate=18169Kbps; SNR Margin Down=10.4dB, Up=15.1dB
(7214749.510000) CHAP authentication successful
(7214749.440000) CHAP Receive Challenge
(7214749.440000) Starting CHAP authentication with peer
(7214749.440000) PPP LCP Receive Configuration ACK
(7214749.430000) PPP LCP Send Configuration Request
(7214749.430000) PPP LCP Receive Configuration Reject
(7214749.430000) PPP LCP Send Configuration ACK
(7214749.420000) PPP LCP Receive Configuration Request
(7214749.420000) PPP LCP Send Configuration Request
(7214697.440000) PTM over DSL is up
(7214660.810000) PTM over DSL is down after 10 minutes uptime
(7214660.810000) PPPoE is down after 9 minutes uptime [Waiting for Underlying Connection (WAN Ethernet 2 - Down)]
(7214657.460000) PPP LCP Send Termination Request [User request]
(7214093.540000) WAN operating mode is VDSL
(7214093.540000) Last WAN operating mode was VDSL
(7214091.930000) PPP IPCP Receive Configuration ACK
(7214091.930000) PPP IPCP Send Configuration Request
(7214091.920000) PPP IPCP Receive Configuration NAK
(7214091.920000) PPP IPCP Send Configuration ACK
(7214091.920000) PPP IPCP Receive Configuration Request
(7214091.910000) PPP IPCP Send Configuration Request
(7214090.510000) PPPoE is up - Down Rate=59921Kbps, Up Rate=18169Kbps; SNR Margin Down=6.5dB, Up=9.3dB
(7214090.490000) CHAP authentication successful
(7214090.450000) CHAP Receive Challenge
(7214090.450000) Starting CHAP authentication with peer
(7214090.440000) PPP LCP Receive Configuration ACK
(7214090.440000) PPP LCP Send Configuration Request
(7214090.430000) PPP LCP Receive Configuration Reject
(7214090.430000) PPP LCP Send Configuration ACK
(7214090.430000) PPP LCP Receive Configuration Request
(7214090.430000) PPP LCP Send Configuration Request
(7214039.800000) PTM over DSL is up
(7213977.800000) PTM over DSL is down after 3932 minutes uptime
(7213977.800000) PPPoE is down after 3931 minutes uptime [Waiting for Underlying Connection (WAN Ethernet 2 - Down)]
(7213974.610000) PPP LCP Send Termination Request [User request]
Time and date
Message
22:42:24, 03 Oct.
(7224548.180000) WAN operating mode is VDSL
22:42:24, 03 Oct.
(7224548.180000) Last WAN operating mode was VDSL
22:42:22, 03 Oct.
(7224546.540000) PPP IPCP Receive Configuration ACK
22:42:22, 03 Oct.
(7224546.540000) PPP IPCP Send Configuration Request
22:42:22, 03 Oct.
(7224546.530000) PPP IPCP Receive Configuration NAK
22:42:22, 03 Oct.
(7224546.530000) PPP IPCP Send Configuration ACK
22:42:22, 03 Oct.
(7224546.530000) PPP IPCP Receive Configuration Request
22:42:22, 03 Oct.
(7224546.490000) PPP IPCP Send Configuration Request
22:42:20, 03 Oct.
(7224545.060000) PPPoE is up - Down Rate=42446Kbps, Up Rate=18169Kbps; SNR Margin Down=9.9dB, Up=8.3dB
22:42:20, 03 Oct.
(7224545.050000) CHAP authentication successful
22:42:20, 03 Oct.
(7224544.740000) CHAP Receive Challenge
22:42:20, 03 Oct.
(7224544.740000) Starting CHAP authentication with peer
22:42:20, 03 Oct.
(7224544.730000) PPP LCP Receive Configuration ACK
22:42:20, 03 Oct.
(7224544.730000) PPP LCP Send Configuration Request
22:42:20, 03 Oct.
(7224544.720000) PPP LCP Receive Configuration Reject
22:42:20, 03 Oct.
(7224544.720000) PPP LCP Send Configuration ACK
22:42:20, 03 Oct.
(7224544.720000) PPP LCP Receive Configuration Request
22:42:20, 03 Oct.
(7224544.720000) PPP LCP Send Configuration Request
22:41:29, 03 Oct.
(7224493.670000) PTM over DSL is up
22:40:52, 03 Oct.
(7224456.630000) PTM over DSL is down after 19 minutes uptime
22:40:52, 03 Oct.
(7224456.630000) PPPoE is down after 18 minutes uptime [Waiting for Underlying Connection (WAN Ethernet 2 - Down)]
22:40:49, 03 Oct.
(7224453.440000) PPP LCP Send Termination Request [User request]
22:21:55, 03 Oct.
(7223319.250000) WAN operating mode is VDSL
22:21:55, 03 Oct.
(7223319.250000) Last WAN operating mode was VDSL
22:21:53, 03 Oct.
(7223317.300000) PPP IPCP Receive Configuration ACK
22:21:53, 03 Oct.
(7223317.290000) PPP IPCP Send Configuration Request
22:21:53, 03 Oct.
(7223317.280000) PPP IPCP Receive Configuration NAK
22:21:53, 03 Oct.
(7223317.280000) PPP IPCP Send Configuration ACK
22:21:53, 03 Oct.
(7223317.280000) PPP IPCP Receive Configuration Request
22:21:53, 03 Oct.
(7223317.220000) PPP IPCP Send Configuration Request
22:21:51, 03 Oct.
(7223315.480000) PPPoE is up - Down Rate=35015Kbps, Up Rate=18169Kbps; SNR Margin Down=10.9dB, Up=-2.1dB
22:21:51, 03 Oct.
(7223315.460000) CHAP authentication successful
22:21:51, 03 Oct.
(7223315.170000) CHAP Receive Challenge
22:21:51, 03 Oct.
(7223315.160000) Starting CHAP authentication with peer
22:21:51, 03 Oct.
(7223315.160000) PPP LCP Receive Configuration ACK
22:21:51, 03 Oct.
(7223315.160000) PPP LCP Send Configuration Request
22:21:51, 03 Oct.
(7223315.150000) PPP LCP Receive Configuration Reject
22:21:51, 03 Oct.
(7223315.150000) PPP LCP Send Configuration ACK
22:21:51, 03 Oct.
(7223315.150000) PPP LCP Receive Configuration Request
22:21:51, 03 Oct.
(7223315.150000) PPP LCP Send Configuration Request
22:20:55, 03 Oct.
(7223260.030000) PTM over DSL is up
22:20:17, 03 Oct.
(7223222.070000) PTM over DSL is down after 0 minutes uptime
22:20:07, 03 Oct.
(7223211.510000) PTM over DSL is up
22:19:07, 03 Oct.
(7223151.290000) PTM over DSL is down after 140 minutes uptime
22:19:07, 03 Oct.
(7223151.290000) PPPoE is down after 139 minutes uptime [Waiting for Underlying Connection (WAN Ethernet 2 - Down)]
22:19:03, 03 Oct.
(7223148.020000) PPP LCP Send Termination Request [User request]
19:59:08, 03 Oct.
(7214752.960000) WAN operating mode is VDSL
19:59:08, 03 Oct.
(7214752.950000) Last WAN operating mode was VDSL
19:59:07, 03 Oct.
(7214751.160000) PPP IPCP Receive Configuration ACK
19:59:07, 03 Oct.
(7214751.150000) PPP IPCP Send Configuration Request
19:59:07, 03 Oct.
(7214751.140000) PPP IPCP Receive Configuration NAK
19:59:07, 03 Oct.
(7214751.140000) PPP IPCP Send Configuration ACK
19:59:07, 03 Oct.
(7214751.140000) PPP IPCP Receive Configuration Request
19:59:06, 03 Oct.
(7214751.090000) PPP IPCP Send Configuration Request
19:59:05, 03 Oct.
(7214749.520000) PPPoE is up - Down Rate=39120Kbps, Up Rate=18169Kbps; SNR Margin Down=10.4dB, Up=15.1dB
19:59:05, 03 Oct.
(7214749.510000) CHAP authentication successful
19:59:05, 03 Oct.
(7214749.440000) CHAP Receive Challenge
19:59:05, 03 Oct.
(7214749.440000) Starting CHAP authentication with peer
19:59:05, 03 Oct.
(7214749.440000) PPP LCP Receive Configuration ACK
19:59:05, 03 Oct.
(7214749.430000) PPP LCP Send Configuration Request
19:59:05, 03 Oct.
(7214749.430000) PPP LCP Receive Configuration Reject
19:59:05, 03 Oct.
(7214749.430000) PPP LCP Send Configuration ACK
19:59:05, 03 Oct.
(7214749.420000) PPP LCP Receive Configuration Request
19:59:05, 03 Oct.
(7214749.420000) PPP LCP Send Configuration Request
19:58:13, 03 Oct.
(7214697.440000) PTM over DSL is up
19:57:36, 03 Oct.
(7214660.810000) PTM over DSL is down after 10 minutes uptime
19:57:36, 03 Oct.
(7214660.810000) PPPoE is down after 9 minutes uptime [Waiting for Underlying Connection (WAN Ethernet 2 - Down)]
19:57:33, 03 Oct.
(7214657.460000) PPP LCP Send Termination Request [User request]
19:48:09, 03 Oct.
(7214093.540000) WAN operating mode is VDSL
19:48:09, 03 Oct.
(7214093.540000) Last WAN operating mode was VDSL
19:48:07, 03 Oct.
(7214091.930000) PPP IPCP Receive Configuration ACK
19:48:07, 03 Oct.
(7214091.930000) PPP IPCP Send Configuration Request
19:48:07, 03 Oct.
(7214091.920000) PPP IPCP Receive Configuration NAK
19:48:07, 03 Oct.
(7214091.920000) PPP IPCP Send Configuration ACK
19:48:07, 03 Oct.
(7214091.920000) PPP IPCP Receive Configuration Request
19:48:07, 03 Oct.
(7214091.910000) PPP IPCP Send Configuration Request
19:48:06, 03 Oct.
(7214090.510000) PPPoE is up - Down Rate=59921Kbps, Up Rate=18169Kbps; SNR Margin Down=6.5dB, Up=9.3dB
19:48:06, 03 Oct.
(7214090.490000) CHAP authentication successful
19:48:06, 03 Oct.
(7214090.450000) CHAP Receive Challenge
19:48:06, 03 Oct.
(7214090.450000) Starting CHAP authentication with peer
19:48:06, 03 Oct.
(7214090.440000) PPP LCP Receive Configuration ACK
19:48:06, 03 Oct.
(7214090.440000) PPP LCP Send Configuration Request
19:48:06, 03 Oct.
(7214090.430000) PPP LCP Receive Configuration Reject
19:48:06, 03 Oct.
(7214090.430000) PPP LCP Send Configuration ACK
19:48:06, 03 Oct.
(7214090.430000) PPP LCP Receive Configuration Request
19:48:06, 03 Oct.
(7214090.430000) PPP LCP Send Configuration Request
19:47:15, 03 Oct.
(7214039.800000) PTM over DSL is up
19:46:13, 03 Oct.
(7213977.800000) PTM over DSL is down after 3932 minutes uptime
19:46:13, 03 Oct.
(7213977.800000) PPPoE is down after 3931 minutes uptime [Waiting for Underlying Connection (WAN Ethernet 2 - Down)]
19:46:10, 03 Oct.
(7213974.610000) PPP LCP Send Termination Request [User request]
Hi there,
Line tests have picked up on a high resistance line fault, I've raised it with Openreach for you and have added an update to your account here: https://www.plus.net/wizard/?p=view_question&id=194797351 please let me know when you've responded.
Adam
Thanks for the post tonyb55. Sounds like quite a pain! I sure hope I don't have the same. 😕
Best of luck with your issue (I hope it doesn't keep returning). I'll let you know if I find anything useful or that fixes the issue in case it's the same cause for you. If you could do the same I'd appreciate it. 
Hi adrianspringer,
Hopefully this will help provide some context for the terms being used.
I will say that the longer the disconnecton issue persists, the worse the impact on your speed will be due to Automatic Digital Line Management (DLM) utilised at the exchange.
Cross Talk
This interference occurs at the Cabinet (the big green box you are connected to).
It is noise that is generated on the connections within the cabinet that leaks onto other lines. Its similar to the noise you sometimes hear when you move your mobile phone close to a radio (am or mw at least)
The effect is to muddy up the signal that is being sent to and from your modem.
Both the modem in your house and the modem in the exchange expect to hear a nice clear note say for instance an E (using C Major C-D-E-F-G-A-B) but sometimes gets a D other times an F which it doesnt know what to do with some waits for the information to be sent again.
The effect at best is to slow down your speed and increase your latency.
RFI (Radio Frequency Interference)
Heres the method that engineers used to (some still do) use and some sources.
https://www.youtube.com/watch?v=iW0ZXh5pIoA
HR (High Resistance) Joint Issue
Not sure if this is of any use?
https://www.ispreview.co.uk/story/2011/06/23/bt-improves-high-resistance-fault-testing-for-uk-unbund...
SNR (Signal to Noise Ratio)
The target Signal-to-Noise Ratio (SNR) margin is particularly important in defining your broadband download speed. It effectively defines the buffer required in signal-to-noise ratio to protect your broadband connection from the fluctuations that can occur over time in signal and noise levels. Poorer lines tend to require higher target SNR margins to avoid regular disconnections.
The exchange equipment attempts to set the downlink connection speed such that there is a sufficiently high SNR margin to guarantee a reliable connection (without regular drops and/or an unacceptable number of errors). This specific margin that the exchange tries to achieve is called the target SNR margin. The higher the target SNR margin, the lower your connection speed.
To summarise, you want as low a SNR as is possiible such that your line remains stable.
The higher the SNR the slower your speeds will be.
| Effect of target SNR margin on downlink connection speed | |
|---|---|
| Downlink target SNR margin (dB) | Downlink connection speed (kbps) |
| 18 (worst case) | 3008 |
| 15 | 3616 |
| 12 | 4096 |
| 9 (TalkTalk's initial default) | 4768 |
| 6 (BT's initial default) | 5568 |
| 3 | 6240 |
| 1 | 6624 |
Original Article
https://www.increasebroadbandspeed.co.uk/SNR-tweak
Microfilter
Did i read correctly that you are using the microfilter?
You have a Fibre Broadband package?
Using a Plusnet Hub?
Heres the guide to master sockets
What type of master socket have I got?
The master phone socket is the main socket where the phone line enters your home, usually found in the hallway near the front door. If you can't find it, have a look outside for any wires entering your home, then look for a white box on the wall inside.
If you have more than one socket, the master socket is the one that will feed any extension sockets. It's always best to connect your Hub to the master socket if you can. This is where the broadband signal is strongest, before it goes through any other home wiring which could cause interference.
This is usually what an extension socket looks like. If all your sockets look like this, then one of them will be your master socket. It's most likely to be the one nearest where your line comes into your home.
Master socket with a single socket
If your master socket has one socket, like this:
You must use a microfilter for every phone socket in your home with any phone or broadband equipment plugged in (including your Hub, phones, answer machines, digital TV boxes, and alarm systems).
A microfilter is a device that allows broadband to work at the same time as your phone service.
Master socket with two sockets
If your master socket has two sockets, like this:
This means that the line is already split between your phone and broadband, so you don't need microfilters - not for your Hub or any other devices connected to phone sockets or extensions.
You must always plug your Hub into the broadband connection on your master socket. If you plug it into a phone socket or extension, it just won't work.
Plusnet Hub
It is worth pointing out that the Plusnet Hub (which is a combined Modem and Wireless Router) has a rather poor reputation both for reliability and especially for Wireless performance.
It is in fact a refaced BT Home Hub 5a with some firmware tweaks that make it even less attractive.
You can easily and cheaply replace it with a, used, BT Smart Hub 6 for around £10 from a particular website....
Which is really easy to set up to run your Plusnet Package.
|
BT Smart |
Plusnet |
|
 |
 |
|
| Complete Wi-Fi | No | No |
| Number of antennas | 7 | 5 |
| Wi-fi bands (2.4GHz and 5GHz) |
Dual Next generation AC wi-fi |
Dual AC wi-fi |
| 2.4GHz wi-fi band | 3x3 11b/g/n/ac | 2x2 11b/g/n |
| 5GHz wi-fi band | 4x4 11a/n/ac | 3x3 11a/n/ac |
| Built-in 4G filters | Yes | No |
| Connections | 4 x giga ethernet | 4 x giga ethernet |
| USB ports | Yes | Yes |
| On/off light control | Yes | No |
| Removable password card | Yes | Yes |
| Smart Wireless | Yes | Yes |
| BT Smart Scan | Yes | Yes |
| Dect | No | No |
Other Noise Types - REIN / SHINE / RFI/ EMI / PEIN /
More Useful Information
~ Introduction to IP profile
Before we start talking about IP profiles it is important to understand the following:-
- Connection Speed or Sync Speed:
The rate at which your broadband service connects to the exchange or DSLAM at and is the maximum speed your line can achieve for transferring both data and any data overheads. - Overheads:
When data is transferred it will always have an amount of overheads. These overheads are wrappers around the data to ensure safe delivery - Similar to an envelope around a letter, they are the labels which tell routers where to send the data.
These overheads can come from various Internet protocols such as TCP/IP or ATM. Data can have more than one wrapper depending upon they type of data and how it is transferred over the network. The original data which is encapsulated (wrapped) may be referred to as the payload. - Throughput Speed:
Throughput speed is the real time speed when you perform a speed test based on the useful data and without overheads. Throughput speed can vary depending upon various factors such as how busy (congested) certain network links are, or how fast the other end can send the data to you.
So to recap: Connection speed is the maximum rate for data transfer including any overheads, whilst throughput speed is based on how quickly the useful data (minus overheads) is being transferred.
~ What is an IP profile?
Your IP profile is related to the BT wholesale bRAS profile and is an indication of the maximum throughput speed your line can attain whilst that particular profile is in place.
The IP profile is a limit put in place calculated from your sync speed, minus an allowance for various protocol overheads. The profile is applied at the BT bRAS to restrict the downstream data traffic speed on the backhaul between the bRAS and DSLAM.
IP profile stands for Internet Protocol profile and should be a guide to the maximum speeds you see when performing a speed test.
For users on a 21CN exchange, the IP profile is calculated as 88.2% of your sync speed.
For FTTC/VDSL2 it is calculated as ~ 96.8% of your sync speed.
~ Why does BT apply an IP / bRAS profile?
The simple answer is to stop traffic bottle-necking at the exchange backhaul VP (or SVLAN for FTTC).
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.
~ How is my IP profile monitored?
| IP profile management is one of the duties performed by RAMBO as part of the RAP (Rate Adaptive Profile) process. Each time the line synchronises to the exchange, the DSLAM's Management Device will process and store information about your line rate. This information is then sent to the bRAS over NCAS RAMBO then sends this information to the bRAS where the profile is applied. |
 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. |
|
~ How can I find my IP Profile?
You can find out what your IP profile is currently set at by performing a PERFORMANCE TEST
| 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. |  |
~ How is my IP Profile calculated?
BT Wholesale use three different methods to calculate your IP profile. This depends 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 due to the more recent products using PTM which has less overheads than ATM.
- NGA System - For FTTC / VDSL / Fibre / Infinity
Uses the Quantisation System that should dynamically adjust the IP profile at each resync.
The calculation is based upon your current sync speed minus an allowance for TCP overheads.
From observations, BT would appear to be using approx 96.8% of the sync speed to calculate the IP profile for the FTTx products.
Please note that if your DLM profile is set to Retransmission High, then this figure will be nearer 91% to allow for the additional overheads.
- 21CN System - For ADSL2+ / WBC Products (Up to 24Mbps ADSL)
With effect from late 2011, BT introduced a new Quantisation DLM system that results in much quicker updating of the IP profile. The calculation is based on your last sync speed minus an allowance for TCP & ATM overheads. The calculation should always be a fixed rate at 88.2% of your sync speed.
~ How often does it change?
How often your IP profile changes, depends upon your type of product:-
- NGA System:
VDSL & Fibre products use the quantisation method so should be able to respond to any changes in sync speed quite quickly. - 21CN System:
ADSL2+ products for users on 21CN exchanges will utilise the quantisation method, so should be able to respond to changes in sync speed quite quickly.
Your IP profile will continually change 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.
~ NGA 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 therefore more efficient throughput.
Because of this PTM framing, the overhead allowance required for FTTC is much less than on 21CN products and is usually in the region of 3.2%.
It has also been observed that lines which have G.INP retransmission applied, then the allowance for overheads is in the region of 3.3%.
This figure may vary very slightly depending upon framing parameters negotiated by the modem and DSLAM and can depend upon the chipset in use. This is also why you may see some modems sync at say 79,987 rather than 80,000 kbps.
Because the IP Profile makes an allowance for overheads, any lines which have Interleave High or G.INP High Retransmission DLM Profiles will find the additional redundancy increases the total overhead allowance to circa 8-9%.
If you have access to your line stats you can check the profile for re-transmission under Bearer 0:
INP Rein 0 = Re-tx low
INP Rein 1 = Re-tx high
~ What is my FTTC sync speed?
Consumers who were issued with an Openreach ECI or Huawei modem have no way of accessing line stats without unlocking these modems. However, it is possible to reverse engineer an approximate sync figure from your FTTC profile. This method may vary by a few kbps due to reverse rounding and the afore mentioned framing parameters, but it should give you a rough idea.
Accuracy can be improved if you know you are on a Huawei cabinet and are using a BCM based modem.
Bald Eagle1 first discovered that using the figure of 96.79% gave high rate of accuracy when using a HG612 and he also noticed in 2015 that it was 96.69% for lines which had G.INP applied.
It has been proven in March 2016 that these exact figures do not work with Lantiq based devices (such as the ECI modem/HH5A) - regardless if you are on a Huawei or ECI cabinet.
~ WBC Banded Profiles for 21CN adsl2+
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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. |
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| NGA for VDSL / FTTC | ||||
| 21CN ADSL2/ADSL2+ and 21CN WBC ADSL | ||||
| 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 |
| 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 |
~ "Stuck bRAS profile"
Although not quite so common these days as when adslMax was first introduced, there is still the odd occasion when a line seems to get what is known as a stuck bRAS profile. It is rare to see a stuck bRAS profile on 21CN or NGA.
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.
https://kitz.co.uk/adsl/IPprofile.htm