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[waltergmw]

Gentlefolk,

In the following links you'll see the synchronised but unauthenticated Diagnostic data from the same 2Wire 2700 HGV modem using a capped 576 down and 288 up Tiscali Globespan DSLAM ADSL 1 service and then a single combined picture using an O2 ADSL2+ Broadcom DSLAM service.

The line length is about 4.5 Km using BT's estimate of cabinet distance from the exchange.
It's interesting to note that:-
The Downstream Attenuation @ 300 KHZ on ADSL1 was 62.3 dB and 58.5 dB on ADSL2+ but some of that might be due to re-jumpering in the exchange
The Downstream Sync speed on ADSL1 was 2472 Kbps and 3568 Kbps on ADSL2+
There are quite large changes in bit loading too with Tone 111 being the highest ADSL1 and Tone 155 on ADSL2+ including a few at the dizzy heights of Hexadecimal E which I've never seen before in Ewhurst.
The O2 service in mid evening gave a TBB download throughput speedtest of 2,700 Kbps.

These data were collected about a week apart both in mid evening.

Carying on from earlier discussions, note that tone 64 shows 2 bits on ADSL2+ and the upstream bit loading seems to be of a more conventional shape rather than being clipped.

Does anybody know the significance of the different bit loading colours ?



http://www.scribd.com/doc/30203832

http://www.scribd.com/doc/30203834

http://www.scribd.com/doc/30203831

http://www.scribd.com/doc/30203830

http://www.scribd.com/doc/30203597

Kind regards,
Walter

[kitz]

>> Does anybody know the significance of the different bit loading colours ?


Perhaps just an aid for viability. I find the colours a bit hard to see, but they all seem to go green, green, blue, black, black.

[kitz]

>>> ADSL1 was 62.3 dB and 58.5 dB

You'd normally expect the attenuation to rise when moving to adsl 2+, because (most) lines will be able to make use of more frequencies, therefore the average across the whole useable range will drop.   You dont see such a marked increase (if any) on short lines.

The bit loading will also change on adsl2+, as it is able to use tones which can load just 1 bit, whereas a minimum of 2 bits are required for adsl1

[waltergmw]

@ Kitz,

I mentioned the 2Wire attenuation drop as I realised that it contradicted your description.
I am using the 2Wire without authentication which perhaps affects the reported results?

I note from the log data that there are a vast number of system operations involved when initiating a 2Wire connection; probably far more than there are on a standard modem.
Potentially these might also affect the reported data?

Kind regards,
Walter

[kitz]

Where the previous stats when on adsl1 also taken from the same router?
It would be interesting if you had an adsl1 & adsl2+ bit stats and bit loading for direct comparison to see if that gave any clues.

>> I note from the log data that there are a vast number of system operations involved when initiating a 2Wire connection; probably far more than there are on a standard modem.

No..  its  just that some routers report far more of the different processes that occur during the sync up phase. 
All routers will go through the same process.... its just that most dont make this information readily available to the EU.
That sort of thing depends upon the firmware, and whether its available by a GUI.. or telnet.. or other means.

I used to have one router which could even report when the DSLAM was experiencing VP congestion.

[kitz]

here you go...   I knew I had something on the site somewhere.

This shows the (26) stages involved during the sync & authentication process for BTw based ISPs.
http://www.kitz.co.uk/adsl/images/l2tpauthentication.gif

The LLU process will be slightly different, but it should give you an idea that theres a lot that goes on that we would never normally know about.
Please note that that also doesnt include such things as bRAS profiling + DLM, which will also occur.

[waltergmw]

@ Kitz,

Thanks very much. ADSL technology is indeed much more complicated that it might at first seem !

I suspect my use of the same modem on all sorts of LLU and other ISP's BT W connections is a bit unusual and can't follow any more than the sync process in most cases.
I should have plenty more opportunities to compare BT's ADSL1 and ADSL2 services once the exchange is enabled (promised initially for Q1 2010 !)
I think I get other log errors for things such as the BT Fusion second wireless channel as well as failures due to non BT supplied services.

Kind regards,
Walter