I missed the attainable bit, that was only mentioned in the first post, not the second (the one I replied to) where he only mentions losing 30Mbps.

yeah I think you will get nowhere, I caused myself loads of hassle for nothing trying to fix something similiar.

Few things to consider. The 25% in 14 days things means openreach should come out and have a look but thats it, they can still easily say "nothing we can do line passes test".
It has to be actual speed, a line that has a 150 attainable dropping to 120 attainable is 0 speed loss.
If line is still above estimated speed then I think there will be an even harder time getting something done about it.

In my case I had a estimated speed of 65.9, the sync started out at 80 with 110 attainable. A 25% speed loss would need it to go below about 60. So I would have needed to lose 50 attainable speed. Instead I had 2 large drops of attainable a week apart from each other, both within a month of my line going live. I first went from 110 to 90, then the 2nd time from 90 to about 73. My effective speed loss was from just 80 to 73, not even 10%. I didnt report it. However later another issue occured on my line which was causing bursts of errors in the early hours of the morning, and DLM was pushing my line down to speeds below 40mbit. This I did report. BT showed up said they couldnt find a fault, JDSU passed etc. the engineer also claimed a 80mbit sync is impossible and I was mistaken I originally had a 80mbit sync, and that the install day 110 attainable he was in complete denial. After he gone, the early morning issues mysteriously dissapeared, in addition my line stopped occasionally jumpng to 90 attainable (prior to visit my attainable kept jumpng up to 90mbit). I used a fritzbox 3370 to accelerate DLM reverting my line and I ended up with for a while on a sync in the high 60s until about 2 weeks ago the attainable went back up to 73-74.

Personally I would be surprised if you had a 2nd FTTC line installed on he same dropwire and had no affect on sync speed on the 1st line.

I share a dropwire with my neighbour who has FTTC, I had a extra engineer visit (after I told BT I am a samknows tester, they decided I merited another visit) this engineer installed a new dropwire dedicated to myself, my attainable shot up to a speed higher than my install day. But then the area manager made him undo the work stating its against BT policy, so I am back on the shared dropwire.

I'm in the same boat but consider if you really need failover or you want to bond them.

The only sensible option for failover is to take an ADSL line back to the exchange, so I have a second line on ADSL at 2mbps and the primary FTTC at 60mbps.

The speed differential is huge making the ADSL line useless, however I really wanted backup (however slow) and two FTTC lines to the same cab is not really backup.

Although FTTC service is flawless so far I can't view that box at the end of my street as long term reliable as the kit at the exchange. I appreciate that I don't have two diversely routed physical wires but hey-ho, this is all you can do at home.

I have underground ducting and when I enable the second ADSL line it has a tiny effect on the FTTC line, maybe a 1mb or two from attainable. (Not the same as a second FTTC line I know but for comparison)

I'm using pfsense firewall to terminate the links and load balance.

Thanks for that really helpful article. I'm starting to understand some of the pain you must have felt when your line went bad and there's no reason for it other than crosstalk. Then to be told by BT that it's not policy to have a dropwire exclusively serving your property is definitely not customer friendly. I guess we all live in hope that vectoring will be adopted and rolled out quickly by BT.

Looking at all the posts it seems to suggest that it's quite likely that an additional line with ADSL/VDSL is likely to affect the existing service, so I think it's unwise for me to start paying for additional services when they might adversely effect my existing low latency connection.

FTTP seems to be the way for me even with it's relatively high setup costs. As an additional question... The Fiber aggregation node that Openreach talk about. Is that usually at the FTTC cabinet, the original CAB or somewhere entirely different. I only ask because my CAB is about 130m from my house and the FTTC cabinet about 90m.

In reply to a post by Magsy:

The only sensible option for failover is to take an ADSL line back to the exchange, so I have a second line on ADSL at 2mbps and the primary FTTC at 60mbps.

And what happens when a failure occurs on the cabling from house to cabinet or the duct from cabinet to exchange?

The only way is fully diverse routing.

Separate drop wire to a different pole. From pole to a different cabinet and from that cabinet to a different exchange.

Yeah I agree... and in my case I could make at least one alteration to my setup which would make it more resilient to power failures (which we've had a fair few recently) by fitting a UPS.

But yes I guess we'd have to define what type/level of resilience we're after and how much it costs to implement.

I have two FTTC lines, one Sky and one BT. I ordered the BT line 2 days into a 5 day internet outage when Sky tried to switch my existing ADSL to FTTC (long story...).

They both connect to the same cabinet so there is not much in the way of diversity. However when Sky is congested or goes offline then I have BT, and vice versa. So protection against provider outage, but not local issues.

The new BT line was wired into a spare pair of wires in the existing phone cable (which, incidentally, had already been used for Sky but were switched).

I use pfSense on a commodity PC (though expensive Intel NICs), which provides WAN load balancing. It doesn't work for everything, of course, but surprisingly many protocols split their requests and often provides around 90% of total bandwidth. The speed test on this site will report ~28MBit/s for the single HTTP thread and 54 for the 6x threaded test. Of more value is the ability to send latency-sensitive protocols down the 6ms BT line and have stuff like video use the 30ms Sky line.

I have not noticed any significant issue with crosstalk. My Sky line dropped from 31 to 26MBit/s in the two months before getting the BT line installed, and has remained there since. This is probably due to other people getting FTTC - I was first on my cabinet. The BT line hasn't moved from 28Mbit/s since installation.

thats good to hear.

In reply to a post by nOw2:

I use pfSense on a commodity PC (though expensive Intel NICs), which provides WAN load balancing.

pFSense seems to be a good choice from your post and some of the stories I've read elsewhere. It probably handles PPPoE connections more efficiently. I like the report graphs too.

BT and Sky seem to be a popular combination. I wonder what makes your Sky line have such poor latency compared to the BT line.

I was told by another poster here it's because the lines are different, but as mentioned they have actually been physically switched. I didn't have the energy to argue.
I've always seen poor latency on Sky, even on ADSL - where Zen provides 14ms Sky was 25ms. My FTTC was provided at 20ms then jumped to 30ms after an IP renewal (!). I just put it down to Sky's network - I'm at the end of their rather ramshackle network in north Wales.
I would actually not recommend using Sky if you use the line for business (their T&Cs actually forbid it) but you definitely want an LLU provider and Sky do have a network about as separate from BT as it's possible to be.