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21CN line but mode is ADSL2 not ADSL2+

mjdenham
Dabbler
Posts: 16
Registered: ‎02-01-2008

21CN line but mode is ADSL2 not ADSL2+

Hi,
I am a bit confused about the relationship between 21CN, ADSL, and ADSL2+.
My DG834GT router tells me I am connected using ADSL2 mode but I thought that since I was on 21CN I would be using ADSL2+.
Do I just need to tell my router to connect using ADSL2+ or do PlusNet need to reconfigure something at their end?  I am using DGTeam firmware and can select a single Modulation Mode but currently I have left all connection enabled which is the default.
Here are my line stats showing the mode among other things:
/usr/sbin/adslctl: ADSL driver and PHY status
Status: ShowtimeRetrain Reason: 8000
Channel: FAST, Upstream rate = 1167 Kbps, Downstream rate = 6240 Kbps
Link Power State: L0
Mode: ADSL2
Channel: Fast
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 14.9 6.6
Attn(dB): 26.0 13.5
Pwr(dBm): 0.0 12.4
Max(Kbps): 7520 1172
Rate (Kbps): 6240 1167
G.dmt framing
K: 196(0) 36
R: 0 0
S: 1 1
D: 1 1
ADSL2 framing
MSGc: 59 12
B: 195 35
M: 1 1
T: 1 4
Thanks
Martin
6 REPLIES
itsme
Grafter
Posts: 5,924
Thanks: 1
Registered: ‎07-04-2007

Re: 21CN line but mode is ADSL2 not ADSL2+

ADSL2 use frequencies that will give a synce speed up to 8mbps and ADSL2+ extend the frequencies so that a sync speed up to 20mbps is attainable. If the higher frequencies are not available because of attenuation or SNR then the modem/exchange will only sync using the lower frequencies of ADSL2.
matt_2k34
Grafter
Posts: 1,300
Registered: ‎09-07-2007

Re: 21CN line but mode is ADSL2 not ADSL2+

Quote
I am a bit confused about the relationship between 21CN, ADSL, and ADSL2+.

OK mate lets try and help that.
ADSL2 and ADSL2+ are two technologies, the difference is the top speed available as itsme has stated-  ADSL2+ uses higher frequencies on the phoneline.
Problem with higher frequencies is that they do not perform well over long distances (my not be heard, or undistinguishable from 'noise' meaning your BB cant use them Sad )
the equipment for 21CN basically adapts the use of ADSL2 or ADSL2+ ... because of the length of your line, im not suprised your only seeing ADSL2
(this is not a problem, perfectly normal) Smiley
if you want to understand the jargon behind it - then looky here http://en.wikipedia.org/wiki/ITU_G.992.3/4
MrC
Grafter
Posts: 523
Thanks: 2
Registered: ‎17-07-2008

Re: 21CN line but mode is ADSL2 not ADSL2+

Quote from: Matt_2k34
because of the length of your line, im not suprised your only seeing ADSL2
The OP's router is reporting a downstream attenuation of 26dB which works out at under 2km. That's actually not very long at all and shouldn't preclude ADSL2+ being negotiated at a pretty decent sync rate (anything up to 17mbps given ideal conditions). I'd be looking at the usual suspects (wiring etc) and trying out a different router (or even the same router on the latest stock firmware!).
Also,  ADSL2 (G.992.3) can give a theoretical down sync rate of up to 12mbps.
matt_2k34
Grafter
Posts: 1,300
Registered: ‎09-07-2007

Re: 21CN line but mode is ADSL2 not ADSL2+

Quote
reporting a downstream attenuation of 26dB which works out at under 2km

My apologies, didnt see that-
Quote
Also,  ADSL2 (G.992.3) can give a theoretical down sync rate of up to 12mbps.

Theoretically yes, but you'd have to have a very short clean line to do so.
MrC hit the nail on the head though - ensure that you have nothing which could be interfering with the phoneline. (e.g. electricals near master socket)

You shouldnt have to flash the firmware back to stock though - the DGTeam one should be fine!
mjdenham
Dabbler
Posts: 16
Registered: ‎02-01-2008

Re: 21CN line but mode is ADSL2 not ADSL2+

Hi,
Could the high Target SNR (15dB) be preventing an ADSL2+ connection?
Thanks
Martin
MrC
Grafter
Posts: 523
Thanks: 2
Registered: ‎17-07-2008

Re: 21CN line but mode is ADSL2 not ADSL2+

Not of itself - it's another symptom.
The lack of ADSL2+ negotiation is more likely to be a problem limiting the bit loading across all the available channels (basic difference between ADSL2 and 2+ is that the latter doubles the number of potential bits per channel). The modems have negotiated an ADSL2 connection so we know your link supports at least some of the higher frequency channels that ADSL2/2+ uses over ADSL1.
Starters for 10 (if you haven't already tried them Smiley ) - use the test socket in the master BT box (if available) to eliminate the house phone wiring and extension devices and see if things improve. If not then leave connected in the test socket and turn everything else electrical in the property (apart from the modem/router and PC!) and retest. Also make sure the modem/router is as far away from the PC as possible.
This is assuming that there's no audible noise on a quiet line test and that the modem/router telephone cable and microfilter are in good nick - faults with these aren't always obvious so worth trying alternatives if you have them.