My BT2700HGV experience

[Arctophile]

My exchange is due be upgraded to ADSL2+ by the ender of the year but I currently use a Speedtouch 585v6 router, which I understand may prove problematical with some new exchange equipment.  For this reason (plus the fact I enjoy fiddling) I thought I would obtain a 2700HGV and see what I made of it.  Courtesy of Ebay (£12 inc p&p) I am now the proud owner of a 2700HGV v6, manufactured in week 43 of 2008, firmware 6.1.1.48.

I set it up using the notes from http://bt2700hgv.tripod.com and worked from my old Win 98SE desktop PC using IE6. 

To start with it failed to connect to IDNet.  After the "Re-attempting" screen the "Broadband link is not currently available" screen was displayed.  I had not previously changed the router password as suggested in the notes, so I changed the password and tried again – with the same result. 

Hmm... thought I.  Then, sitting there looking at the router, I noticed that the Internet light was solid green.  Restarted IE6 and bingo – internet access was available.

The Sync Rate/BT Profile are one step below the values that the Speedtouch has consistently achieved over the past two years. 

BT2700:  7616/6500kbps     Speedtouch:  8096/7000kbps

I thought that the speed reduction might have been caused by the 2 or 3 reboots during the installation process but after nearly five days and one reboot there has been no change.  The reported noise margin varies slightly (14db – 15db) compared with the consistent 12db previously reported by the Speedtouch.

What's better, larger or smaller noise margin value?

My current connection figures are as shown below.  Any thoughts on this speed reduction?

                  Down       Up
Rate:          7616 kbs    448 kbs
Max Rate:    10168 kbs  1052 kbs
Noise Margin:  15.0 dB   24.0 dB
Attenuation:   23.1 dB   12.0 dB
Output Power:19.8 dBm 12.1 dBm
Protocol:G.DMT Annex A

Channel:Interleaved

DSLAM Vendor Information  Country: {46336} Vendor: {TSTC} Specific: {0 }
ATM PVC:0/38

Rate Cap:10168 kbs

Attenuation @ 300kHz:23.1 dB

Uncanceled Echo:           -13.3 dB      Ok
VCXO Frequency Offset:  -15.5 ppm    Ok
Final Receive Gain:            7.4 dB       Ok
Impulse Noise Comp. Tones: 0            Ok
Excessive Impulse Noise:     0             Ok

After nearly five days I rebooted the HG2700 to see if any changes occurred.  This process took nearly 10 minutes during which time the power light flashed red.  I understand that this means the unit is being upgraded; sure enough the firmware has upgraded itself from 6.1.1.48 to 6.1.1.48.1.

A couple of further points of interest:-
1.  After I rebooted the BT2700 I reconnected wirelessly from my Vista laptop.  Despite internet access becoming available the little globe symbol was not showing on the internet icon in the system tray.  In addition the router logs showed that it had tried to connected to www.msftncsi.com .   Google tells me that this is a Microsoft site that Vista uses to confirm internet connectivity and then display the globe symbol.  After a reboot of the PC the symbol reappeared.

2.  When accessing the router pages via IE8 on my laptop, above each page I get the following message:  "Intranet settings are turned off by default... Click for options".  Should I worry about this?

Sorry for the long post,

Bob, (long time lurker).

[Rik]

Hi Bob, and welcome to the forum. The change is sync speed is because interleaving has been turned on, the exchange has seen the repeated connection attempts as instability. Give support a call, they can arrange for it to be turned back off again (but note that this is a 'once in a lifetime offer', if the system turns it back on, BT will not generally switch it off a second time).

In other respects, your line is to die for, maximum sync speed with a lot of headroom on your noise margin (9db over the normal 6db target).

Can't help on the Vista stuff, sorry.

[Ray]

  Bob, and I'm afraid I can't help with the Vista stuff either, but I'm sure there will be someone along later who can. 

[MisterW]

Hi Bob,
I suspect interleaving has always been on and its just that the Speedtouch can support S=1/2 mode ( see quote from Kitz below )

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).

As Rik says, your line should support 8128 no probs and there's really no reason why interleaving should be on.
My line has an attenuation of 31db and synchs at 8128 with a margin of 8db using a 2700 ( v5 ).

[Arctophile]

Many thanks for the comments.

I presume that the interleaving will not, in time, resolve itself then?

Out of interest I will try the Speedtouch tomorrow to see what happens with the sync rate etc.

We had a short powercut just after my first post; the router rebooted in less than a minute this time.  The figures are all similar to the previous values except that the noise margin has gone up to 16db.  Larger is better then?

The problem with the Vista internet icon was repeated; I suspect that the PC was trying to connect before the router had finished its internal workings.

[rireed3]

the noise margin has gone up to 16db.  Larger is better then

Only if you are at a maximum sync 

[Simon]

The problem with the Vista internet icon was repeated; I suspect that the PC was trying to connect before the router had finished its internal workings.

I have the same symptoms with my Vista laptop sometimes, and occasionally it requires a reboot, or refuses to connect at all.  Like you, I assumed it was something trying to connect too quickly, so I disabled MailWasher from startup, and that didn't really help, but as it only does it once in a while, and I don't use the laptop all the time, I'm not that bothered by it.

[MisterW]

I presume that the interleaving will not, in time, resolve itself then?

Not in my experience it wont!

except that the noise margin has gone up to 16db.  Larger is better then?

As rireed3 says, Yes , and you are at maximum synch with interleaving enabled.
In reality the difference 15 to 16 db is probably due to the time of day when it resysnched. You would expect a 1-2db variation during the day with lower values towards the evening and maximum in the morning.

[Arctophile]

Well, Brian at IDNet kindly asked BT to switch off interleaving for me.  I am now synchronising at 8128kbps with a 13db noise margin.

A BT speedtest shows the following:-

   Your DSL connection rate: 8128 kbps(DOWN-STREAM), 448 kbps(UP-STREAM)
   IP profile for your line is - 6500 kbps
   Actual IP throughput achieved during the test was - 6105 kbps   

I presume that the profile will rise given time.

It is interesting that the Speedtouch router could synchronise at 8128 kbps with interleaving switched on but the BT2700 could not.

Bob

[Rik]

Welcome to the black arts they call comms.

[rireed3]

I may have an answer for this from the Technical Discussions board.  See ADSL Noise Margin High!.  It seems that Speedtouch supports "S=1/2 mode which effectively combines two RS code words", and that gets back the interleave coding delay.

Richard

[Rik]

I told you it was a black art.

[quandam]

As far as I can see no one has asked you how long your line is (could be wrong). From personal experience the 2700 offers little if you have a short line from the exchange. I have a short line and found little or no difference when using the 2700. My personal opinion (for what its worth) is that the 2700 offered by BT as an item, is, in line with BT 's history of poor products etc.and fits that bill perfectly. However, others will tell you that the 2700 is the best thing since sliced bread for their purposes and I would not argue against those.

Just my opinion on the 2700.

[Rik]

You're right, Q, the biggest benefits from a 2700 come to people with long/poor lines. If you have a good line, almost any router is fine.

[MisterW]

I have a short line and found little or no difference when using the 2700.

It really depends on how short... If you have a line with an attenuation of say 25db or less then you're probably right, however when you get switched to ADSL2+ then things might be different!!
My experiences with 2700's:-
My own line, 31db attenuation, Belkin router could never synch above 7000 and I had to manually fix a 9db target SNR ( giving 6400 synch ) to stop it dropping out 2 or 3 times a day, 2700 holds 8128k rock solid with 8db SNR.
A friends line >63db attenuation, never synched with supplied Talktalk (sorry about the bad language!) router, synchs at 2500 with a 2700.
Office outworker, a rural line with 56(ish) attenuation, on a fixed 1mb speed with a 1800HG, gave about 8db SNR max but was dropping the line frequently in the afternoons, a 2700 gives 20db SNR max and the line is rock solid.
Now ADSL2+... Our office line, 12db attenuation, used to synch (obviously!) at 8128k with a DG834, got converted to ADSL2+ (Demon LLU I believe) and was a little unstable at 20Mbps, put a 2700 in there and a nice stable 22Mbps with a 9db target SNR.
   

[quandam]

I can't argue with that reply. Mainly because I don't understand 99% of it If you are happy then so be it!

[Arctophile]

As far as I can see no one has asked you how long your line is (could be wrong).

Whilst I am in a rural location I am fortunate that the exchange is only about 1.2km from my house.

Just a little clarification - it looks like the Speedtouch could sustain a synchronisation of 8096kbps (not 8128kbps) on my interleaved line where the BT2700 could sustain 7616kbps.

The BT2700 is now achieving 8128kbps without interleaving; I haven't got round to re-trying the Speedtouch since interleaving was switched off.

I am not sure of the significance of attenuation but it is now 22.2db.

Bob

[JB]

You're right, Q, the biggest benefits from a 2700 come to people with long/poor lines.

In my case, with a short stable line, it shows a more 'steady' noise margin. IOW it sits at either 10 or 11 db. Whether this is just damping of the results I don't know, because other routers show a more varying figure between 7 and 12 db.

If you have a good line, almost any router is fine.

Agreed.

[Rik]

In my case, with a short stable line, it shows a more 'steady' noise margin. IOW it sits at either 10 or 11 db. Whether this is just damping of the results I don't know, because other routers show a more varying figure between 7 and 12 db.

I don't think so. It was definitely more stable for me than a Netgear, and held sync for 3-4 times as long. On WBC, however, it reports a slightly wavering NM, so it is sensitive enough to detect the changes.

[JB]

Sorry Rik. Are you saying that you don't think the noise margin is damped slightly?

[Rik]

I don't think it is, JB, but I have no way of testing beyond trying different routers and, a bit like the signal meters on Sky boxes, they all seem to have their quirks.

[JB]

they all seem to have their quirks.

They do Rik. The only reason I thought it was damped was because I don't see such large swings in noise margin on the 2700 as I do on my other routers. OTOH, the 2700 may talk better to the DSLAM and it may actually be maintaining a more stable noise margin.

I'm very pleased with the 2700. These are the figures:-

DSL Connection Details
DSL Line (Wire Pair):    Line 1 (inner pair)
Protocol:    G.DMT Annex A
Downstream Rate:    8128 kbps
Upstream Rate:    448 kbps
Channel:    Fast
Current Noise Margin:    10.0 dB (Downstream) 23.0 dB (Upstream)
Current Attenuation:    28.7 dB (Downstream) 15.0 dB (Upstream)
Current Output Power:    19.8 dBm (Downstream) 12.3 dBm (Upstream)
DSLAM Vendor Information:    Country: {0xB5} Vendor: {TSTC} Specific: {0x00}
PVC Info:    0/38

The noise margin always seems to be 10 or 11 db.

[Rik]

Are you sure you don't want to give me that line, JB?

[Arctophile]

Just a little update...

Five days after interleaving was switched off my BT profile finally clicked up to 7150kbps – the max possible under ADSL max.  I am now typically getting a real world throughput of over 6000kbps with a steady noise margin of 13db.

According to the logs the router has also stopped trying to contact BT every 45mins or so; it now only tries at about 03:00hrs each day.

The router is also obviously up to something else though; the following message continually appears in the System Log:-

     lmd:  hostap2: couldn't sync config: No such file or directory
     nodesd:  unable to sync data: No such file or directory
     nodesd:  Previous log entry repeated 280563 times

The repeat number varies depending on how often I check but the router appears to be in a continuous loop.  It doesn't seem to affect the performance.

Does anyone have any thoughts on what it is trying to do?  I suspect that is something to do with its failure to talk with the BT servers.

Bob

[Rik]

I'm guessing you're right, Bob, it seems to be looking for the firmware update file.