Can two ADSL connections interfere with each other

Hi,

I have a personal and a work phone line into my house both with ADSL (although from two different ISPs). The work line and its ADSL was put in as an up-to-8meg service last year. Originally, I had intended to cancel my personal ADSL but the service on the work ADSL line was so poor (averaging around 1.5meg even though I am about 800 metres cable length from the exchange) that I decided to keep my personal 2meg service running.

Last week my ISP changed my personal line from the rock-solid 2meg service to the up-to-8meg service and, although the training period doesn't finish until Tuesday, I've seen that also drop to below 2meg.

The interesting thing is that when the personal line was changed over, i saw the work line drop to an average of half a meg for a couple of days. It could be coincidence but it made me wonder whether the two are linked in some way and that I have created a vicious circle - keeping the personal line because of poor performance on the work line and getting poor performance on the work line only because I am keeping the personal line.

With the personal line performing as badly now, I have no problem with cancelling it if any of you believe it could be part of the problem. Alternatively, is there any way I can get a line reverted to the reliable to 2meg service? Another option is to move to Sky as they are offering an up-to-16meg service locally but I suspect many of you will warn me off Sky generally and, if it is the same rate adaptive system, it will probably get restricted down to the same level anyway.

Any advice is welcome.

Regards,

Dave

Crosstalk is certainly possible, and is probably inevitable to some extent.
So see if there is any effect you could try the following.
Obtain lines stats (attenuation, noise margins, power levels etc) from each line while both active. Then disconnect one modem and see if the other line stats improve.
Then try the other way round.
May give an indication if there is a problem distinct to these 2 lines.

Thanks Rogan for the really quick response.

I have the stats from my personal router as I was already trying it with my work router disconnected since about 10:30 this morning. These figures don't mean anything to me but perhaps they provide some clues for you. I will do the same comparisons on the work router later and report back again (although my other router does not report stats in exactly the same way I'm afraid).

These are figures since I disconnected my work router and reset my personal router at about 10:30AM this morning.

Line Status: Downstream / Upstream
ADSL Link Speed: 7616 kbps / 448 kbps
SNR: 3.5 dB / -
ATEN: 15 dB / 12 dB

Line Error: Downstream / Upstream
ADSL layer FEC: 59 / 1377
ADSL layer CRC: 3 /161
ATM layer HEC: 5 / 154
Frame Counter: 29913 / 25028
Loop Distance: About 3 K ft


These are figures from before I disconnected my work router. I am not sure when my personal router had last been reset before this.

Line Status: Downstream / Upstream
ADSL Link Speed: 7136 kbps / 448 kbps
SNR: 2.5 dB / -
ATEN: 15 dB / 13 dB

Line Error: Downstream / Upstream
ADSL layer FEC: 10 / 15074
ADSL layer CRC: 1 /18
ATM layer HEC: 2 / 17
Frame Counter: 305715 / 377814
Loop Distance: About 3 K ft

As ever, any advice welcome.

Dave

OK, I now have the other stats, as I said, in a dfferent format as determined by router model.

Although I don't know what the figures mean, it does look to me like the figures on both are worse when they are both connected than when the other is off. Does that mean that I should cancel my personal connection and, if I did, would I need another 10 day training period? Which line should I choose to have my one connection on?

These are the figures for my work connection with my personal router disconnected...

Upstream Noise Margin:

relative capacity occupation: 0%
noise margin upstream: 6 db
output power downstream: 19 db
attenuation upstream: 18 db
tone 0- 31: 00000005566656665655556666666660
tone 32- 63: 00000000000000000000000000000000
tone 64- 95: 00000000000000000000000000000000
tone 96-127: 00000000000000000000000000000000
tone 128-159: 00000000000000000000000000000000
tone 160-191: 00000000000000000000000000000000
tone 192-223: 00000000000000000000000000000000
tone 224-255: 00000000000000000000000000000000


Downstream Noise Margin:

relative capacity occupation: 0%
noise margin downstream: 4 db
output power upstream: 12 db
attenuation downstream: 29 db
tone 0- 31: 00000000000000000000000000000000
tone 32- 63: 00222222222222222232233233222222
tone 64- 95: 02233333333333333333334344444444
tone 96-127: 44444444444444444444444444444444
tone 128-159: 44444444444444444444444444444444
tone 160-191: 44444444444444444444444444444444
tone 192-223: 45545555555555555555555555555555
tone 224-255: 55555555555555555555555555555555


ATM Status:

SAR Driver Counters Display:
inPkts = 0x000008b7, inDiscards = 0x00000001
outPkts = 0x000006b6, outDiscards = 0x00000000
inF4Pkts = 0x00000000, outF4Pkts = 0x00000000
inF5Pkts = 0x00000001, outF5Pkts = 0x00000001
openChan = 0x00000002, closeChan = 0x00000000
txRate(Bps) = 0, rxRate(Bps) = 0


WAN Port Statistics:

Link Status: Up
Upstream Speed: 384 kbps
Downstream Speed: 2720 kbps
Node-Link: 1-PPPoA
Status: Up
TxPkts: 1747
RxPkts: 2254
Errors: 0
Tx B/s: 0
Rx B/s: 0
Up Time: 0:11:41



These are the figures for my work connection when both routers are on and connected...

Upstream Noise Margin:

relative capacity occupation: 0%
noise margin upstream: 6 db
output power downstream: 19 db
attenuation upstream: 19 db
tone 0- 31: 00000005566555655555556556665650
tone 32- 63: 00000000000000000000000000000000
tone 64- 95: 00000000000000000000000000000000
tone 96-127: 00000000000000000000000000000000
tone 128-159: 00000000000000000000000000000000
tone 160-191: 00000000000000000000000000000000
tone 192-223: 00000000000000000000000000000000
tone 224-255: 00000000000000000000000000000000


Downstream Noise Margin:

relative capacity occupation: 0%
noise margin downstream: 6 db
output power upstream: 12 db
attenuation downstream: 28 db
tone 0- 31: 00000000000000000000000000000000
tone 32- 63: 00222222222222222222222222222222
tone 64- 95: 02222222222222222232333333333333
tone 96-127: 33333333343333333333333333333333
tone 128-159: 33333333333333333333333333333333
tone 160-191: 33333333333344444443434344444444
tone 192-223: 44444433333444443333444444444444
tone 224-255: 44444444444445555555555566666666


ATM Status:

SAR Driver Counters Display:
inPkts = 0x000000b3, inDiscards = 0x00000000
outPkts = 0x000000d5, outDiscards = 0x00000000
inF4Pkts = 0x00000000, outF4Pkts = 0x00000000
inF5Pkts = 0x00000000, outF5Pkts = 0x00000000
openChan = 0x00000003, closeChan = 0x00000001
txRate(Bps) = 0, rxRate(Bps) = 0


WAN Port Statistics:

Link Status: Up
Upstream Speed: 352 kbps
Downstream Speed: 2112 kbps
Node-Link: 1-PPPoA
Status: Up
TxPkts: 241
RxPkts: 202
Errors: 0
Tx B/s: 0
Rx B/s: 0
Up Time: 0:06:13

Thanks for your help,

Dave

Your two ADSL connections should work quite happily together.

I have two such connections (as per my signature) and they do not interfere with one another in any way at all.

You probably should be more concerned with an ISP which messes about with your connection without giving you sufficient notice.

Assuming that both sets of figures relate to your personal router, there is no strong evidence that the work router is interfering with the personal router. Would you care to declare the ISPs and a little more about your setup - particulalrly your premises wiring and whether your lan is wired or wireless?

Sort out your house wiring, with low attenuation figures like that, you should have the full 8mbit sync, and more snr than that.

Thanks Sandgrounder,

It is good to know it can be done then. Does the fact that yours work necessarily mean that this is not the source of my problems though? Could it be that we are connected differently to the BT network meaning I have problems and you do not? Or is it just that I have to live with this because I have poor line quality even though I am only 800m from the exchange?

Regards,

Dave

Thanks pitnicker,

I'm sorry if I misled - the first posts figures relate to my personal router firstly without my work router being on and then with both being on. The second set of figures relate to my work router, firstly on it's own and then with both on.

I do have a wireless lan but my tests are going through CAT5 cabling. Both routers exist on the same subnet but I configure devices to connect to .1 or .2 depending which route I want to use. I have no devices with two network cards and no devices use both connections simultaneously - it is either/or.

My work connection is through Vodafone. My personal connection is through Metronet.

Regards,

Dave

Thanks Dave2150,

Are you saying that it is my extensions on my personal line? As I say, I have no connections other than the ADSL itself on the work line and yet that is getting the same sort of performance (admittedly connecting higher but it is still training and whenever I speedtest it is still performing worse than my 2meg service did).

With the personal line, I have one proper point which is from the wall panel under the stairs but it is not a proper BT Master Socket. From that point, Sky have done their normal classy extensions which are just glorified extension leads rather than wall points. I have therefore plugged their extensions in after the filter that goes into this one proper socket - can dodgy wiring after a filter on voice extensions still cause problems if they are after the signal has been filtered?

You obviously understand these figures. If I unplug everything apart from the two routers, should I see an immediate change to these figures and what figures should I expect? If I don't see a change, are the figures sufficiently bad for me to get BT out to investigate?

Sorry to ask so many questions today.

Regards,

Dave

Edited by daveok1 (Sun 28-Jan-07 16:45:59)