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Author Topic: Help - speeds and router questions...  (Read 26614 times)

Helpneedadvice

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Help - speeds and router questions...
« on: June 17, 2008, 02:17:41 PM »

Hi, hope someone can help. I would love some clarification about what I should be expecting from speeds and whether changing my router might help.

Please excuse my lack of correct terminology on here - this broadband stuff is all new to me but I've been reading around this excellent site and the Hmmm site of B4dgers and am learning fast.

Some history: I have been having problems with speeds from my ISP. Once upon a time when I first signed up to the 8M service with my ISP (around 18 months/2 years ago) I noticed that I was syncing at about 6.5Mbps and I paid little further attention to it. My browsing was fast and efficient and I was happy.  Over the last year or so, my browsing has become a lot slower. I only found the time to start looking into why a few months ago and realised that I have been getting more like 3.5Mbps sync and hence associated lower throughput during this time. (The change I believe coincided with when my ISP moved me off BT equipt and onto Tiscali equipt at the exchange). Throughout all of this, I was just using a simple Speedtouch 330 modem for my broadband.

When I reported the problem a few months back, speedtests showed that  I was getting particularly low throughput even for those sync speeds  and my ISP insisted I try a router instead of my modem, so I borrowed a Netgear DG834 from a friend. No difference experienced,  so after more months of messing around, my ISP decided to  move me back onto BT equipment. But then things got worse; I started getting a fixed 2Mbps sync instead!

More months of messing around and many further speedtests later, my ISP finally agreed it could be a fault and sent a BT engineer out. He found they had indeed set me up on the 2M service rather than the 8M service (we had suggested this to the ISP but they had said they had checked with BT that it wasn't the case - well obviously it was!); this got me back up to the 3.5M sync service that I was experiencing on the Tiscali equipt. I also smiled sweetly at him and he went away and changed my line pair to a lovely new copper one while he was about it. (Line attenuation immediately went down from 39dB to 33 dB as a result :))

This was Fri morning. Immediately, I noticed a difference: I started syncing mostly at 7-8Mbps. Hooray! However, that evening during busy hours, I started experiencing some loss of syncs (SNR fluctuated between 5 and 0, possibly lower), but 99% of the time I would resync immediately up to that level and only received one lower sync rate of 6200kbps. As a result my IP profile went down from 7000 to 5500 :(.This morning I disconnected briefly and set up a Speedtouch 585v7 router that I just purchased as I read it was more less sensitive to losing sync. It synced at 7200kbps with 5dB noise margin. Just now (Tues lunchtime) I checked and suddenly I am getting only 5088kbps and my SNR is up to 15dB and hence my IP profile is now getting lower and lower.   I am currently in the 10 day training period (day 4/5) and so I am worried that my MSR will be set unrealistically low as a result.

I have had great arguments with my ISP because they gave me a fault threshold of just 1.8M on my line previously when they set me up wrongly on the BT equipt recently as a 2M user by mistake. They kept telling me that BT would not accept it as a fault because my throughput was above this! I am very keen that a realistic MSR is set for me to avoid future conflict.

So now I finally get to my point (sorry about the waffling). What speeds does anyone think that should I be expecting?

I live 700m as the crow flies from the exchange in a small market town. My ISP said my previous line length was 2.2km (a bit long?) from the exchange (I was getting attenuation of 39dB and noise margin around 12 dB). My new line is only 33dB attenuation and so hopefully taking a shorter route to the exchange. It is also a nice new copper one and not aluminium. On connection I got 7-8Mbps at 5dB SNR immediately.

I am still syncing mostly at over 7000kbps and this morning I reached the dizzy heights of 8032 kbps with 5dB Noise margin. I disconnected briefly a few times to set up the new router, resynced after set up at 7200 (at 5dB) and when I get back from lunch find I am now down to 5088kbps (at a non-busy time of day) with a 15 dB noise margin. Why have they turned my noise margin up so high in one go? Would BT have done this because i disconnected earlier and as a result I lost sync over lunch, or would I have lost sync over lunch and then this happened? I am wondering if it was an enforced loss of sync or the router didn't cope. It seems a funny time of day for traffic noise to be the cause.

I just disconnected and reconnected and got the same result.

Can anyone please help me understand what is going on? My ISP said my speeds will vary in the first 10 days but the lower speeds are surely not good news for my MSR and furure fault reporting, particularly if it was caused just by my disconnections to set up the new router. Also I read that if the SNR exceeds 15dB, it gets stuck up there and doesn't come down by itself. So my speeds will be even lower.

Thanks folks!


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Helpneedadvice

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Re: Help - speeds and router questions...
« Reply #1 on: June 17, 2008, 02:20:51 PM »

"This morning I disconnected briefly and set up a Speedtouch 585v7 router that I just purchased as I read it was more less sensitive to losing sync"

Sorry should read less sensitive to losing sync  :)
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Helpneedadvice

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Re: Help - speeds and router questions...
« Reply #2 on: June 17, 2008, 02:38:59 PM »

Oh I have another question on my new speedtouch 585 router. Mine only came with a quickstart guide. I don't yet find the user interface as friendly as the Netgear one. I am trying to find where to set it up to poll for stats every 5 secs or so like on the Netgear one. Currently I am having to refresh the page repeatedly which is a bit of a pain.

Also is there a way to timestamp the logs? Currently it shows time since connection, but since i am emailing the logs to my ISp when necessary a proper timestamp as per the netgear router would be really useful. Many thanks :)

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roseway

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Re: Help - speeds and router questions...
« Reply #3 on: June 17, 2008, 02:51:40 PM »

Hi and welcome.

The way the BT system works, if the connection is deemed to be unstable then the target noise margin (the margin which is applied at the time of synchronisation) is increased in 3 dB steps until it becomes stable. The highest target noise margin is 15 dB. After synchronisation the noise margin will drift up and down depending on the level of interference on the line. The actual noise margin can go above 15 dB and no, if that happens it doesn't get stuck there.

It look as though you have a problem with varying levels of interference on your line, and what possibly happened during that lunch period was that there were several bursts of interference causing frequent re-syncs, so that the target noise margin ended up getting bumped right up to the maximum.

There are any number of possible reasons for this, and I suggest that you have a read of this and the associated pages to see if you can home in on the cause.

The web interface of the Speedtouch routers is pretty awful I'm afraid, and I don't think it's possible to make it refresh the stats in the way that you want. They are pretty good routers though.

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  Eric

Helpneedadvice

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Re: Help - speeds and router questions...
« Reply #4 on: June 17, 2008, 04:04:21 PM »

Thanks for replying... I know it isn't my internal wiring (problem occurs even when plugged into the master socket) and it's not my router/modem (loss of sync problem is present with both of them). There is nothing electrical suddenly coming on in the house or as far as I can tell from the neighbours either. In fact the weird thing is that apart from Fri evening (when I would expect a drop might occur) the connection was pretty stable over the weekend. I live in a residential area, no factories nearby etc. Is it possible that the noise could be coming from the exchange/ line from the PCP to the exchange? If so, is there anything I can do about it?

I read about interleaving. Would that be turned on as default by BT? Maybe I should check it is with my ISP.
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b4dger

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Re: Help - speeds and router questions...
« Reply #5 on: June 17, 2008, 05:49:37 PM »

I can recommend RouterStats free software to monitor your SNRM/Sync. The site doesn't mention v7 but I think it will work fine - just point it to the stats page.

See the link in my signature to see the graphs it makes...

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Helpneedadvice

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Re: Help - speeds and router questions...
« Reply #6 on: June 18, 2008, 06:28:20 AM »

Thanks B4dger! Do you manage to get a timestamp with your graphs?
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b4dger

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Re: Help - speeds and router questions...
« Reply #7 on: June 18, 2008, 09:17:43 AM »

Thanks B4dger! Do you manage to get a timestamp with your graphs?

Yes, the bottom of the graph shows the 'timeline'...
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Helpneedadvice

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Re: Help - speeds and router questions...
« Reply #8 on: June 20, 2008, 07:40:37 AM »

B4dger

I just read something you wrote on another site, that with interleaving switched on, the max sync you can get is 7616. My ISP tell me that interleaving is switched on but I have had had a sync at over 8M. Does that make sense?

Thanks - I see the timeline on the graphs now by the way - duh! silly me. Do you know of anyway to get the speedtouch to display the time on its own stats page. Am i missing something? I'm finding the "time since last boot" hard to decifer compared to the Netgear.
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roseway

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Re: Help - speeds and router questions...
« Reply #9 on: June 20, 2008, 07:57:40 AM »

According to the BT documentation, interleaving does limit the sync speed to 7616. However in many cases it seems that this doesn't happen, and people get higher connection speeds up to the maximum 8128. This seems to happen mainly on short lines with plenty of margin to spare.

Regarding the 'time since last boot' issue, have you got the router set up to get its time by NTP? I'm not using a Speedtouch at the moment, so I can't check, but I rather think that this is what you need to do. If you have to specify a time server in the setup, I usually use uk.pool.ntp.org
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  Eric

b4dger

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Re: Help - speeds and router questions...
« Reply #10 on: June 20, 2008, 11:31:02 AM »

Helpneedadvice, don't believe 'everything' I write  ::)
As roseway mentions the max interleaved speed does depend on your line, so can vary.


roseway - thanks for the 'time tip' I've just added the server you quoted and changed my router log to show the actual time rather than time since startup - much better.

It's a shame the Speedtouch log only logs very basic events - unless someone knows how to make it more verbose?
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roseway

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Re: Help - speeds and router questions...
« Reply #11 on: June 20, 2008, 11:52:58 AM »

It's a shame about the Speedtouch web interface generally in my opinion. They make excellent routers with rotten interfaces. :(
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  Eric

Helpneedadvice

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Re: Help - speeds and router questions...
« Reply #12 on: June 20, 2008, 02:15:56 PM »

Thanks roseway - i just changed mine too. At least i can see when my loss of syncs occur now!

Would you say a line of 33dB would count as a short line with plenty of margin to spare? My noise margin at the time was 5 dB but it has since risen to 16.5 dB due to all the loss of syncs that i keep getting. It's really frustrating as I didn't get these loss of syncs before the engineer put me on this shiny new copper pair and fiddled around at the exchange. However, the old pair had it's own problems; it was aluminium for a start and took a longer route to the exchange. (Previously I was on a 39dB line which they told me was 2.2km long - it seemed rather long as I am only 700m from the exchange as the crow flies - isn't the multiplier meant to be 1.5 or something?)

My ISP asked BT if I had previously been put on the 2M service and they said no, turned out i had. Now they are saying interleaving IS on, but i just wonder...

My husband has a separate line on a computer right next to mine with BT as ISP. He gets the full 8M and he is also getting an attenuation reading of 33dB, so possibly he is using the same bundle or at least similar. He gets no loss of sync due to noise.
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roseway

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Re: Help - speeds and router questions...
« Reply #13 on: June 20, 2008, 03:34:58 PM »

33 dB attenuation isn't particularly low; it's around the level at which you might or might not get the full 8 megs connection speed, depending on the level of interference. If you're getting fairly frequent re-syncs then you will almost certainly be interleaved (enabling interleaving is the first thing that's done to improve the stability of a connection).

Your distance from the exchange is no measure of the line length, as it's quite common for lines to follow indirect routes. Your present attenuation of 33 dB is consistent with the line length of 2.2 km that they told you. The previous aluminium cable would have had a higher attenuation, so 39 dB was about what would be expected.

To find out why your connection is unstable while your husband's isn't, you'll need to do some diagnosis as indicated in the link I gave you earlier. Good luck! :)
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  Eric

kitz

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Re: Help - speeds and router questions...
« Reply #14 on: June 20, 2008, 04:42:43 PM »

Taken from the main site on the Interleaving page

Quote

It should also be pointed out that whilst BTw state that applying interleaving shouldn't reduce your line speed, it does reduce the maximum line rate achievable from 8128kbps to 7616kbps due to the additional overhead required for check bytes.
Note: although BT state 7616 is maximum sync speed with Interleaving, many instances of higher sync speeds have been reported by users. This is dependent upon your router being able to support S=1/2 mode which effectively combines two RS code words into a larger logical code word of 510 bytes (ANSI T1.413).

Interleaving and Error Correction are always switched on at the same time and the 7616 profile has a 512kbps error correction overhead with an increased latency of around 16 ms.


Obviously as eric correctly says it also depends on you having sufficient overhead to be able to sync at the higher speed....
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