Old cables and vdsl vectoring

R

raivo

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May 14, 2012
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Hi,

My question is, how much internet speed and connection quality can affect cable lenght and type installed at home?

We have adsl internet since 2003 so inside house from street there goes phone cable with slighty thicker wires, then about 25 meter long telephone 4 wire cable, from which about 8 meters are unnecessary spare, at the end the cable is split into two parts with two wires each going into RJ11 connectors->modem, then telephone line goes all the way back through the same cable where it is linked with a short phone cable to the wall outlet nearby and from there goes another 10 meter long 4 wire cable to the next room outlet, where finaly is plugged our only stationary phone.

Assuming that the cable lenght outside house to the nearest DSLAM is within or close to the outer borders for VDSL(2) max distance and I have currently very stable and constant 15Mbit/2Mbit internet speed (limited by ISP, because they said 20Mbit is too noisy or unstable, something like that, I don't remember exactly) with nice 6ms ping. My 40 meter away neighbour house on the same street have 20Mbit.

Is it worth trying to replace the old 25 meter long 4 wire phone cable inside the house with 10 meters shorter and more in VDSL specs cat5 twisted cable and run phone line through seperate cable and is there even slightest possibility that I will have better chance for higher internet speed (they offer 20Mbit/5Mbit for the same price) and is it worth asking again to test my available internet speed?
 
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I'm having trouble following the whole cable routing situation in your home but yes DSL should be used on one direct cable from the NID to the modem. In the NID you install a filter to prevent the DSL signal from traveling down the other wires to your phones. The phone company should be able to see what speeds they get at the NID and if they can get 20 mb/s at the NID then it must be something with the wiring in the house preventing from you getting that same speeds at the modem.
 
Thank you for the answer. I am not sure what is NID, but some time ago we had problems with internet stability (one and only time) and they tested at the incoming outlet and at the modem and they said that at the NID (point where outside cable connects to the home inside wiring?) signal is good but at the modem side worse.

Is it your mentioned filter or not, but before we had vdsl modem installed there was some kind of splitter (small grey box) with IN and Phone out / dsl out before modem, with the new VDSL modem splitter is gone as the modem have built-in dsl/phone-1, phone-2 out lines - modem is a slighty modificied version of this and with a custom ISP firmware.

My phone wiring is simple, short version - small box that simply connects outside cable to inside cable-25m long 4 wire phone cable, that is splitted in two parts at the other end-both ends goes in to the modem's dsl and phone out jacks-phone signal travels all the way back at the same cable and then through about 3 connection points finnaly reaches phone.

My question is, theoretically, how much such wiring setup can affect vdsl quality and speeds and is it something worse improving to gain, lets say, 20Mbit instead of 15Mbit stable connection? They technically can give me 20Mbit/5Mbit but as I understand it, they cannot quarantee 100% connection stability at these speeds. Will the proper wiring help in my situation?
 
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Mopower is right about how there should be one direct cable from the NID to your modem.

Do you have access to your modem's GUI page? If you do, some modems will show you your max attainable rate and error rates. Before you make any wiring changes, test your modem right at the NID (network interface device) also sometimes known as Demarcation Point or Demarc. Then test it at the different points in your cable run to see which cables are actually affecting your service.

If you don't have access to your GUI, then I would suggest you move your modem as close to your NID as possible with a short phone cord, and use longer cat 5 cables to connect your devices.

I hate to be that pedantic guy... and I'm not sure what context you are using the word "vectoring", but I work in telecomm so....

VDSL vectoring is a technology that uses crosstalk cancellation to improve the rates and reach of xDSL. It isn't in use in full production on any ISP I know of (at least in North America). I know that several ISP are trialling it.
 
That "I would suggest you move your modem as close to your NID as possible with a short phone cord, and use longer cat 5 cables to connect your devices." is a good advice, thanks.

I will look at the modem's GUI but I am afraid my ISP has cut any end user unnecessary futures in the modem interface as it has seperate 'user level' login and master login what they use to configure more specific settings.

Is the NID that small box outside where all telephone cables from nearby houses join together or is it something inside or close to my house alone?

Sorry for not mentioning earlier, I live in a country where we are fortunate to have optical internet but where it is not yet possible due to costs, we are upgrading to VDSL2 starting from this year and for the first time I can have higher speeds than 10Mbit/800Kbit with older adsl technology we had earlier.

You know how ISP specialists, especially customer help by phone, can sometimes be "currently higher speed is not possible at your dsl line because it is not possible and that's all I am going to say to you" not explaining is it something l can't help like too long distance from my house to the DSLAM (is that what they are called?) or bad quality cable outside my house or it is something I can try to fix like shortening distance to the modem, replacing cables inside house etc.
 
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I absolutely recommend upgrading the wire from the demarc to the modem if you can. I've see as much as a 10mbit gain going from cat3 to cat5e on a 6ft run. If you are using quad (4 individual wires, red, green, yellow & black) absolutely upgrade it to cat5e. If you don't have POTS (traditional telephone service) on the line then you don't need a filter in the demarc at all, just a line mod that you'll disconnect all other wires from to hook up the blue/white-blue pair to running directly to the jack at your modem.

If you do have pots then you'll need a VDSL2 filter in the demarc. The blue/white-blue will go to the vdsl output while the rest of your IW will attach to the pots output.

Keep in mind that it might be worth your time paying the phone company to do this for you. usually it runs around $100. Once you get specific with the installer they tend to listen to you a little more. Don't tell them how to do it, just tell them that you want a cat5e home run to your modem and the VDSL2 filtered at the nid.

There is a reason there are companies out there that sell internet/tv/phone bundles that require their installers to run a cat5e home run, it makes things work like they should.
 
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I guess that I don't have those POTS, just a regular single phone with a caller id function and yes, you are correct, only two - blue and white-blue wires are going from the outside cable to the cat3 quad cable up to the modem, other incoming wires are unconnected. Perhaps it adds some aditional dirtyness to the vdsl signal that the analog phone signal is running down from modem by the same cat3 quad cable's rest two wires instead of seperate wire (installers version of saving a little of his time and work back in the old dsl days when internet speeds were slower not exceeding a few Mbits and quality cable instalation were not required).

Thank you for your encouraging answer, I will definitely change cable even if it helps not much, but just to have peace inside that I have done all I could.

Ok, I understand now "For residential services, the demarc is often installed inside the residence in the homeowner's cellar or basement." My provider's cable goes inside house with slighty thicker wires and there is a small box with provaider's logo on it, so yes, I can access my demarc point! Perhaps there is another demarc point outside house where cable connects to another box that goes to a street wide cable, I am not sure about this and I can''t access it.
 
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Today I replaced the old cables and here is modem DSL Connection data

Before:

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After:

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Noticable change is that Output Down Power dropped from 7.2 to 4.9, is that good or bad? My bandwidth is limited from their side. What can you tell me from the images above? Is a cable change good enough reason to call them and ask for test again my line for 20Mbit/5Mbit connection speed stability?
 
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It looks like your modem is showing sync rate not maximum attainable rate. It could be worth your while to call and see as your profile almost always is set lower than your max attainable.

Here's what my modem shows, note the listing of max and current being listed:
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Yes,it is something about sync rate, I am not technician, but as I understand it, at a higher rate they could not guarantee 24/7 internet stability and so that the customers didn't call and put blame on them for unstable internet from time to time, they put sync rate in safe margins. I am only wondering if cable change will do good enough for little higher speeds.
 
So I probably won't get much more upload than that, well that's ok, I am still quite happy what I have now, considering that just one month ago I had only 760Kbit/s upload at best and 9.6Mbit/s down before this upgrade to vdsl.

On a bright side, my CRC Errors (Up?Down) have dropped greatly:

with old cable 0/43 CRC errors in 19 hour uptime
with new cable 0/16 CRC errors in 1 day and 6 hours uptime

FEC errors generate about the same amount in time period as before.
 
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Alright, so the drop in output power is a GOOD thing. What that means is that you are getting the same SNR and download rate but the modem and DSLAM are using less power to get there. Less power being used means that there is more leeway for more power to be used should the need arise. Kinda like a car engine using 30% of its power to go 100 MPH vs using 90% to go 100 MPH. Also less power being used means less crosstalk being generated which is a good thing.

It is unfortunate that your GUI doesn't show attainable. The drop in CRCs (uncorrected errors) is a really good thing (probably due to less transmit power being used). Someone noticed that your upstream attenuation is really high, but that's ok. ATTN measurement (at least for xDSL) is also affected by the frequency it is measured against. So it's really high because upstream is measured on different frequencies than downstream. What's important is that your CRCs are 0. Any amount of FECs are ok as these are corrected errors. HEC errors are also uncorrected errors, but you're looking good there.

Another really important factor for your line is your good SNR measurements. I am not sure about the standard for your ISP, but for mine, we accept a minimum of 6 SNR while we consider a decent SNR 7-10dB and a good SNR is anything above 11. So very simply, SNR drops with getting more speed, or longer loop length (crosstalk will also affect SNR). Since your loop length will stay the same, that means that you can get higher speeds since you have SNR to spare.

There's also 2 main types of VDSL profiles right now with a 3rd one that's not used in many places.

The main ones are 8b and 17a, there's also a 12a in use but I only know of one ISP that uses it. From your rates and SNR with output power numbers, to me it looks like you're on 8b. The thing is, when max attainable measurements are done by the modem, they are done using the profile that it is sync'd on. bds1904's line shows a really high rate and SNR because his modem is using 17a mode. Even though it doesn't show it, I can tell because only 17a has such a high attainable for downstream/upstream. On a really clean phone line, VDSL 17a has down/upstream max of around 80/30 Mbps, for VDSL 8b, it's around 65/10Mbps, for ADSL2+ around 24/5 Mbps. Most ISPs though use profiles that have much lower upstream caps, for my ISP it's 17a - 12 Mbps, 8b - 5Mbps, ADSL2+ - 2 Mbps. That leads me to believe that although your modem is reporting VDSL mode, it is actually sycn'd on a ADSL2+ profile. The max attainable downstream for 2+ is about 24 Mbps. My ISPs caps downstream around 16 Mbps and using VDSL 8b when going for higher than 16 Mbps. Your ISP may use ADSL2+ up to 20Mbps but in our testing, we've found ADSL2+ starts getting unstable arounf that rate so above 16Mbps we use VDSL 2b. I've known some modems to report the highest profile supported vs actual profile in use (VDSL vs ADSL2+ in your case). Keep in mind although theoreticals are that high, ISPs will ALWAYS sell profiles with lower capped rates. This is because line conditions vary (rain, humidity, bad cabling, etc.) and so they must allow for some overhead instead of allowing the line to run near 100% capacity. That way, if your line quality degrades, you won't lose service.

Now, this is REALLY rough guess, but with your attn being 25ish, and your SNR being 16ish at 16 Mbps, and on a ADSL2+ profile I am guessing you are between 2000-3000 feet from your DSLAM. You should be able to get 25-30 Mbps cleanly if they put you on VDSL2. I am not sure about your upstream though. Now, in case I am wrong about your profile, and you are actually on a VDSL profile, then I would say that your "clean" max is probably 20-21 Mbps, which MIGHT be the case since that is what your ISP says it is.

In any case, maybe google search your ISP and look for what profiles other people are on for 16Mbps and then at 20 Mbps.

Wow, sorry for wall of text, this post ended up being a lot longer than I had intended.

:eek:

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Actually I just noticed you said that you have 6ms ping time, which tells me that you are on VDSL2 mode. VDSL2 uses PTM to talk from your modem to DSLAM. ADSL2+ uses ATM which almost has double the latency of PTM so you would not be able to get 6ms ping time if you were on ADSL2+.
 
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I read every word carefully and with interest. Thank you! As for 16Mbit thing, they call it emergency profile (16Mbit/2Mbit) for vdsl2 in places where first real profile 20Mbit/5Mbit (or 10Mbit/2Mbit as minimum) is not available, then next profile is 40Mbit (or 20Mbit/5Mbit as minimum) and finnaly 60Mbit (or 30Mbit/8Mbit as minimum).

If I can go up to 20Mbit, that would be great! I just don't know if my upload is not good at 5Mbit, what they will do? Put me back on 16Mbit/2Mbit or they will be kind enough to edit my own settings to something like 20Mbit/2.5Mbit, if it is even possible.

I give it a try and thank you for spending your time with this post!
 
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If it's a smaller ISP, they may be able to tweak your profile to a specific setting. But for larger ISPs, they go with cookie cutter settings as managing specialized/individualized profiles would be a logistical nightmare.

Without knowing the exact conditions of your line I wouldn't be able to tell you what rates you can get.

You're welcome and good luck with your line!
 
Would it be worth asking the telco to come out and replace the drop? Loosing an extra ~24' of unnecessary wiring on the other end of the demarc could also help the issue.
 
You could try that. But they will most likely charge you to replace the drop unless it's proven that it is the actual drop that is causing the issue to the point where even if on the lowest acceptable profile the connection is unstable.
 
Here is dsl connection stats from other guy who have the same ISP and he says his internet connection is stable with both IPTV's on that consume about 10Mbit and web browsing. If you don't mind, I will post a link to the picture because he have about the same line attenuation. Interesting his CRC errors are on the upload side but mine are on the download side and we both have about the same Up/Down stats. He phoned ISP and they said they raised his connection speed recently and are currently testing for stability.

Seeing his upload speed it does give me some hope although I don't want that high CRC count on upload side and I would be fine enough with little or even no raise from my current 2Mbit upload, but I do hope on some download speed improvement.
 
Yesterday my ISP upgraded my profile to 20Mbit/5Mbit internet plan, I have to wait now and see how stable it will be over time and will I get any disconnects and speed problems.

2zjlz5u.jpg
xlgeia.jpg

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As expected, SN Margin went down, at least on the upload side to little worrying 6.4dB, but as long as everything is stable, I will be fine, right? I do hope I can keep this profile.
 
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Interesting, since I got higher speeds from 16Mbit/2Mbit to 20Mbit/5Mbit, my CRC errors have dropped from arround 40-60 to zerro after 2 days usage now. I don't understand, why? Is it because:

1) higher sync rate with higher frequences has some effect on my line?

2) after speed change from ISP side, while modem was turned off (it was required to restart modem), I rechecked demarc point inside the room and soldered incoming cable to the cat5 cable that goes to the modem. You may ask why? Well, I am perfectionist and if it even makes 0.01% better connection, then why not. Before it was connected usual way with a screw and a joint point. Unfortunately I forgot to check line stats after speed upgrade but before soldering.

Also, should I be worried if my unshielded cable runs to second floor through about 1-2 feet long thick iron tube, cut from both sides, that was left there after house repairs - any possible negative effect on cable? Also, in about 5-6 places cable makes hard 90 degrees turn, but I guess that is fine.
 
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You SNR target for that profile is most likely 9dB on the DS and 6dB on the US. as long as you keep meeting that you should be fine.

As far as the errors go, the "emergency profile" could have been a different type of profile that tends to build more errors verses the interleaved profile you are most likely on now.
 
That might be it, thanks. SNR is running stable at 6.3-6.4dB for the upload side no matter it is evening with heavy traffic going or in the early morning.

Are you are saying SN Margin for the US is at least decent and will not cause internet problems, higher response times for browsing etc. and I am good here as long as it don't drop below 6dB, right? That is good to know as I was little worried here!
 
Correct, as long as you maintain your US noise margin (assuming the target is 6dB minimum as most 8a 12a and 17a profiles are) you should maintain good service.

Take note that your modem is fully achieving the target sync rate for your profile & your SNR's are good. That generally makes for stable service as long as the SNR's are stable.
 
Today, after 7 days running, dsl line went down (including phone) for about 5 minutes, after coming back, upload bandwifth was reduced from 5.076Mbit to 4.890Mbit

Maybe it was seven days learning period or what, I dont know, but I am happy about the fact, that it can automatically adjust itself to the line conditions and I am more confident now that I don't have to switch back to 16Mbit/2Mbit profile but it will reduce speed if something goes wrong, am I right? :)

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