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[Greyt]

I have two adsl lines coming into my office. Both have been running at full 8mbit on Adsl for several years without any issues.

Each line is with a different ISP each with an attenuation of 15-16

My exchange was recently upgraded to adsl2+ and I requested the 1st line to be upgraded to adsl2+ annex m. I got 19 mbit down and 2 mbit up. Line was rock solid for 10 days+

After 2 weeks the second line was upgraded to annex m. For 2 hours I got 13mbit down and 2mbit up. After 2 hours I had 256k down and 512k up (not a typo!). I requested the profile was reset and I ended up with 3mbit down and 2mbit up.

The first adsl connection has since degraded but is still running at 13mbit.

I have carried out all normal diagnostis. Switched routers between lines, used nte test socket, replaced routers to draytek 2830s, replaced filters (high quality adsl nation). Everything indicates an issue with the slower line.

I have requested a sfi2 visit from Openreach since I just want this resolved but I am curious on one thing - the master socket was moved internally by bt several years ago, the second master socket is connected next to the first master socket. Both sockets are connected using a single cable coming into the office from BT. Is there a chance that the Pairs within the cable could be interfering with each other?

[asbokid]

The presence and extent of crosstalk on a pair can be determined from Quiet Line Noise data obtained from the ADSL modem.  Obtaining this data is usually possible with Broadcom chipset devices.  It's useful to have two lines for comparison purposes. Both lines are with different ISPs but are they attached to the same DSLAM at the exchange? Who are the ISPs?  Other line data - e.g. attenuation across the bandplan should illustrate whether this is the cause of the problem.  Two pairs in the same drop cable, in the same cable bundle and terminating on the same DSLAM in the same exchange?

cheers, a

[burakkucat]

Welcome to the Kitz forum.

I am curious on one thing - the master socket was moved internally by bt several years ago, the second master socket is connected next to the first master socket. Both sockets are connected using a single cable coming into the office from BT. Is there a chance that the Pairs within the cable could be interfering with each other?

Highly unlikely. Consider the number of pairs (100s) that are bundled together in the E-side cables which exit the exchange building. They all run together until the PCP cabinet is reached. At that point the numbers of pairs starts to decrease, as different capacity D-side cables feed to different DPs. Having reached the DP that serves your office, undoubtedly via the same E-side & D-side cables, then why should there be a problem with them arriving at your Office from the DP in the same service cable?

[kitz]

If you disconnect all equipment from line 2..  what happens with line 1?  Does the sync speed go back up?

[Greyt]

Thanks for the comments. In answer to suggestions so far :-

switching off one of the connections makes no difference - I suspect I have a stuck profile now though so that it is not easy to see if this is helping. forcing the modem to sync using ADSL rather than ADSL2+ also remains at the same sync speed.

Quiet line data- I am using Draytek routers so dont think I have this option, but will look into this some more. 

My comment on the lines conflicting was based on a limited understanding that the cables need to be twisted to remain balanced. The cables have to be straightened as they go through the first NTE to the second NTE. I know it was a long shot but wondered if this could be an issue....I am struggling to work out any reason why the second ADSL2+ activation has caused such issues - hence looking at long shots even though of course this could all be coincidence.

Both ISPs are using 21CN infrastructure

Fingers crossed that the SFI2 will uncover an issue. Does anyone know if the SFI2 engineer has the option of :-

switching DSLAM
Switching cables used from exchange to property
Resetting BRAS profile / force retraining etc (or does this have to be done by the ISP?)

[asbokid]

Quiet line data- I am using Draytek routers so dont think I have this option, but will look into this some more. 

The Draytek Vigor 2830 apparently uses a Lantiq XWAY Danube-S System-on-Chip. The Danube has a dual MIPS32 core clocked at 333MHz. [1] [2]

The Danube is part of the AR9 SoC family. Lantiq bought the IPR for this family from Infineon who had bought it from Texas Instruments' wireline division.  TI had a reputation for shipping buggy silicon in its DSL CPE series but Infineon and then Lantiq may have have ironed out those gremlins long ago.

Analysing QLN from each end is an obligatory part of the xDSL specs, so every modem must gather QLN tonemap data.

However, there may not be a userspace tool to actually retrieve the tonemaps for human consumption.    The kernel drivers in the Draytek share much in common with the ECI VDSL2 kit being used for CPE by BT Openreach ( ).  The retrieval of QLN, HLOG (line attenuation), SNR and BITS tonemaps is achieved by reading and writing to pipes for a firmware utility called dsl_cpe_control or similar  [3]

cheers, a

[1] http://www.linux-mips.org/wiki/Danube
[2] http://www.lantiq.com/uploads/tx_abzlantiqproducts/PB-e-0029-v1_lres.pdf
[3] http://www.wehavemorefun.de/fritzbox/Dsl_control