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Standard User meditator
(fountain of knowledge) Sat 21-Apr-12 19:46:53
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Anyone throw any light on this strange DNS problem?


[link to this post]
 
This query is addressed to those of you who are experts on ADSL line performance (ADSL1) and the terminating kit at the local exchange.

Just this last week a problem's occurred in which my access to the Internet, both browser and POP e-mail, disappears randomly. When it disappears, it stays disappeared for quite a long time. Some days I've had no Internet access at all. And yet if I log into my router, the line to the exchange is most certainly sync'd and running at a reasonable speed, even though access to the Internet is impossible. THe TCP/IP settings in Windows are all fine. It's a fixed WAN IP address and the router gets the ISP's DNS servers automatically.

If I run the utility DMT, I'm able to see graphically that, at the physical level, there's a connection right back to the kit in the exchange. The only significant clue I have is that my POP3 e-mail client reports when it tries to send mail "The host <my ISP's DNS name> cannot be found". When browsing fails, Windows just reports it, saying it can't find the website.

Initially, the non-access was preceded by my landline phone in the house ringing fast and uncontrollably, including at 2am in the morning on one occasion. Now, I do know that the phone doesn't use the ring wire. Most landline tone-dialing phones don't. So this can't be anything to do with the ring circuit in the back half of the master socket. The phone recreates its own ring circuit purely from the A-B pair, inside the handset.

At the master socket I use an ADSL Nation XTE-2005 master faceplate filter. The one extension line is solely for my wired router and is terminated in an RJ45 socket into which the router's RJ11 lead is plugged. This upgraded wiring arrangement has worked fine for some two years so far. Cabling between the XTE-2005 and the RJ45 is Cat5e and implemented to a high standard..

Testing of the line the other day, conducted initially by me with the BT Faultline (the 151 service), indicated that in the absence of my extension and any of my kit, there was some sort of problem with the voice line. Accordingly, the next day a BT engineer turned up. But he knew nothing about the ADSL Broadband side of things and so he merely conducted a ringing test on his test phone and a line quality
check, which of course showed little or nothing wrong on this 2.5km line. He refused to do any checks at the exchange, though, saying he wouldn't know what to look for. Sod's Law, the phone problem wasn't there when he visited, neither was the ADSL problem. But within an hour of him departing, I'd lost Internet access again.

In my own experiments I've found that if I log in to my router and I nudge the kit at the exchange into responding by me re-entering and applying my Internet login details so as to momentarily take down the 'Internet' indicator on my router, it will restore full operation at all levels. But I lose the Internet if I run DMT and try to re-sync the line to a slower speed, something with which until recently there was no overall problem. The line resyncs and it's all there but there's no actual data-packet communication going on (and so any resolving of IP addresses).

I've double-checked all my physical connections at my end and even re-wired one part, but accessibility is still iffy. I've even restored the router (a wired Netgear DG834) back to its factory defaults and then reconfigured it but it's made no difference.

Personally, I find it difficult to tell whether this might be the router on its way out or whether instead it's down to the terminal kit (DSLAM, etc) at the exchange malfunctioning. The DSLAM has often refused to respond in the past to my router renegotiating the line and it's sometimes taken me several tries with DMT to regain sync. On the other hand, I've begun to wonder if the filter in the XTE-2005 has become damaged by a surge on the line, as I can't see how the phone could have otherwise gone berserk without there being a hard fault on the line.

For a day, I lashed up a bypass arrangement on my XTE-2005 and on my extension wiring, and used a completely independent plug-in type filter for the phone. Everything ran okay. However, I didn't as before remember to force the DSLAM to renegotiate the line, so maybe I need to repeat that particular test.

The real question, though, is: What does that e-mail client error message suggest? Is it saying that the problem lies somewhere within the router, or is it indicating that the problem's somewhere on the far side of the DSLAM? Browsing fails because clearly there's no translation going on (website name to IP).

I've of course been in touch with my ISP about this. My connection at the local exchange is, as far as my understanding goes, an LLU arrangement, as my ISP doesn't have a major presence in that exchange.They say that at present there's no problem further up into the Web in their domain (although a couple of weeks ago, I know that they did have a major e-mail server failure that took a couple of days to fix).

The line to the exchange is wholly copper.

I've primed my ISP that they might need to get, via their own mechanisms, a BT engineer out to the exchange to specifically investigate there and maybe also conduct some meaningful ADSL testing from my end with a BT laptop and router. I had to do that once before, several years ago, and although it was a totally different problem then, it turned out to be a fault at the exchange. Unfortunately, I myself have no alternative router to try. But I'll only press it with my ISP if I can first eliminate my end as being the probable source of the problem.
Administrator MrSaffron
(staff) Sat 21-Apr-12 19:59:00
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Re: Anyone throw any light on this strange DNS problem?


[re: meditator] [link to this post]
 
Your IP traffic is tunnelled to the ISP, so it is not a DNS problem at the exchange.

When you have this problem can you visit a website via its IP address

Andrew Ferguson, andrew@thinkbroadband.com
www.thinkbroadband.com - formerly known as ADSLguide.org.uk
The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Standard User meditator
(fountain of knowledge) Sat 21-Apr-12 20:12:56
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Re: Anyone throw any light on this strange DNS problem?


[re: MrSaffron] [link to this post]
 
Haven't tried that and, right now, it's not worth doing, as everything's working fine.

Remind me about the form. Is it:

http://xxx.xxx.xxx.xxx ?

Know of any suitable IP addresses I can use? TBB's, maybe? Then I'll give it a try tomorrow. Am busy on the Web with something else at the moment.


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Administrator MrSaffron
(staff) Sat 21-Apr-12 20:19:15
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Re: Anyone throw any light on this strange DNS problem?


[re: meditator] [link to this post]
 
http:// 80.249.99.130 which s us

Andrew Ferguson, andrew@thinkbroadband.com
www.thinkbroadband.com - formerly known as ADSLguide.org.uk
The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Standard User XRaySpeX
(eat-sleep-adslguide) Sat 21-Apr-12 22:55:11
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Re: Anyone throw any light on this strange DNS problem?


[re: meditator] [link to this post]
 
I'm a bit confused. When you say:
In reply to a post by meditator:
my access to the Internet, both browser and POP e-mail, disappears randomly. When it disappears, it stays disappeared for quite a long time. Some days I've had no Internet access at all.
do you mean you can't access the Net at all or just you can't get addresses resolved?

If the former then, as you are synced to exchange, then it is an issue with authenticating with your ISP. If just the latter then it's an issue with the DNS you have set. In which case raw IPs, as previously suggested, should work.
In reply to a post by meditator:
"The host <my ISP's DNS name> cannot be found".
Don't understand this! DNS are normally specified by raw IP not name.
an LLU arrangement, as my ISP doesn't have a major presence in that exchange.
Don't understand this either! LLU is quite the reverse; LLU ISPs do have major kit presence at exchange.

If it is a DNS issue as you seem to suspect, why not change to a public DNS and nail it?
Open DNS : 208.67.222.222 & 208.67.220.220
Google DNS: 8.8.8.8 & 8.8.4.4
Norton DNS: 198.153.192.50 & 198.153.194.50
In any case, as you are synced OK to exchange, it has nothing to do with exchange or your local wiring.

1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 19 Meg WBC
Standard User meditator
(fountain of knowledge) Sun 22-Apr-12 00:27:18
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Re: Anyone throw any light on this strange DNS problem?


[re: XRaySpeX] [link to this post]
 
I'll take your responses one by one, XRay:

1) When it happens, I can't get the Net at all. My outgoing POP e-mail message gets as far as my Outbox but then the client says that it can't find the dns e-mail server belonging to my ISP. When Internet access is lost I've no idea if the addresses for either the e-mailing or browsing are getting resolved because no other error reports are available, eg. if the browser (IE) can't access the Net, you just get a standard Windows failure browser page. I'm sure you know the one I mean.

2) The POP e-mail error message names the server (generically) it looks for but can't find. It's one of the ISP's e-mail servers, that's all.

3) All I know is that it's 'some sort of LLU arrangement'. I think my ISP piggybacks my account on to one of the LLU providers. You and others know more about that side of things than I do, I'm sure.

4) Regarding your last comment about it being nothing to do with the exchange or my wiring, you may well be right. But don't forget that this all started by my phone ringing strangely. It was as if a call was coming in, the phone rang but then there were no pauses between the rings. That's to say, it continually rang at a fast rate and even continued for a few minutes like that after I picked up the receiver. It did the same when I was rung back by the BT Faultline people. Knowing that the ringing tone is generated entirely in the phone off the A-B wire pair, it's as if the A-B pair from the exchange was being rapidly modulated, if you see what I mean. So, this may well be a DNS problem but undoubtedly it's also linked with a line problem of some sort that's affecting the phone. I've an identical phone, BTW, which I also tried, and that too became subjected to the rapid ringing. The BT engineer who called mentioned in passing that, some years ago, they had a facility at the exchanges for forcing rapid-ring calls on to customers' lines (goodness knows for what purpose), but he thought it was never used nowadays. To try to re-create this phenomenon, I've used the old BT ringback no. (17070) but thus far the ringback has worked and the phone has rung in the correct fashion, ie. this particular problem's not recurred. The other day, when this was at its worst, a phone contact of mine found that when he rang me he heard the start of the ringing but then the line went dead.

Edited by meditator (Sun 22-Apr-12 00:34:39)

Standard User XRaySpeX
(eat-sleep-adslguide) Sun 22-Apr-12 01:04:00
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Re: Anyone throw any light on this strange DNS problem?


[re: meditator] [link to this post]
 
All I can reply is that I don't know what you mean by a "dns e-mail server". You can either have a Domain Name Server (DNS) or an email server but not a hybrid.

Anyway, I've already advised you to try a public DNS. Also next time problem occurs try raw IPs; having collected some in advance by doing e.g. 'ping bbc.co.uk'

Yes, the strange phone ringing does seem strange, but we can't say if it is connected to your Internet issue until you've eliminated the DNS. It could be just a scam call wink

In Re LLU: Which ISP? Which exchange?

1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 19 Meg WBC
Standard User meditator
(fountain of knowledge) Sun 22-Apr-12 11:06:51
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Re: Anyone throw any light on this strange DNS problem?


[re: XRaySpeX] [link to this post]
 
Right, I've had an opportunity to try a raw IP address or two when the failure occurs. None of the IPs are successful. There's no connection to the Internet from the browser.

The ADSL tones (bits per tones plot), as seen in the DMT utility, look pretty ropey at present. They tail off quite severely in amplitude as you move up the frequency range and there are several big gaps. Mind you, I am on a long line, so that spectrum has never looked very uniform. Synchronisation is still there, and if DMT's figures and those in my router are anything to go by, at a speed, SNR, etc that I normally get.

As I mentioned before, I find I can retrieve access with the Internet if I log into my router and re-apply my Internet login details. When I do that, the 'Internet' indicator (only that indicator) on the Netgear router extinguishes and then returns. This surely means, doesn't it, that the connection through to the Internet has been reset in some way at some position beyond the DSLAM? The 'Internet', as far as that indicator goes, is surely a level beyond my line?

On the more hardware aspect of this problem, I'm mindful that the XTE-2005 contains transistors amongst its filter components. Thus, I've been wondering whether maybe a surge on the line has partially or fully damaged one or more of those semiconductors and that the filter is possibly now loading the line in an abnormal way. Perhaps the line is okay enough to support the tones but if a line resync occurs, resolving of server sites fails?

XRay, you've misunderstood my description of the e-mail server. Its name, in this case, just happens to include the word 'dns'. So, unfortunately I described it as a dns server.

When the e-mailing fails, the full error message that the client gives me is:

The host 'pop.dnsmaster.net' could not be found. Please verify that you have entered the server name correctly. Account 'Skymarket', Server: pop.dnsmaster.net, Protocol POP3, Post 110, Secure SSL: No, Socket error: 11004, Error no. 0x800CCC0D.

Addendum: Do you happen to know whether the equivalent faceplate filter marketed by Clarity uses any transistors? I'm referring to the one here:

http://www.clarity.it/telecoms/adsl_faceplate.htm

Edited by meditator (Sun 22-Apr-12 11:46:02)

Administrator MrSaffron
(staff) Sun 22-Apr-12 12:42:37
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Re: Anyone throw any light on this strange DNS problem?


[re: meditator] [link to this post]
 
How does a faceplate failure cause a loss of IP throughtput, but the ADSL layer remain? That is assuming the noise margins remain sensible at above 3dB 99.999% of the time

The issue you appear to have is an authenticated session going stall, and a drop of the PPP session appears to resolve this. I would advise stop worrying about the ADSL hardware.

The problem may be a factor of the modems software behaviour so worth trying a different modem.

Andrew Ferguson, andrew@thinkbroadband.com
www.thinkbroadband.com - formerly known as ADSLguide.org.uk
The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Standard User XRaySpeX
(eat-sleep-adslguide) Sun 22-Apr-12 13:23:27
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Re: Anyone throw any light on this strange DNS problem?


[re: meditator] [link to this post]
 
Well, that simple test has eliminated any DNS issue.

'dnsmaster.net' is an unfortunate, and stupid, domain name for an ISP's domain. No wonder you are confused.

Your ISP, Skymarket, is not LLU going by the speeds it sells. It resells BTw ADSL Max BB. Or is it just your email host?

Everything points to an issue with your ISP's Authentication Server (LCP/PPP), remote from the exchange.

I agree with MrSaffron to forget the ADSL hardware, other than trying another router, and cut down on the wordy expositions. It is difficult for us to see the wood for the trees.

1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 19 Meg WBC
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