ADSL "mode"

P

PsyCLown

Expert Member
Joined
Dec 23, 2006
Messages
1,190
Reaction score
5
Location
JHB North
Hi guys,

So been a while since I last had ADSL due to various reasons.
Finally got a line again today and I noticed that by default my one router set the mode to ADSL2+ and the line would sync fine although display 4092 / 511 as the sync speed.

My other router was set to G.DMT by default and my line would then sync at 4096 / 512.
I changed the other router's ADSL mode to G.DMT and it then synced at 4096 / 512 and still works fine.

So now I am wondering which is the preferred mode, the better one to use and why?
Does it make any difference? One strange thing I noticed is that when I am doing a speedtest, my download speed never seems to exceed 3.50Mbps - tried with the Telkom guest account and then WebAfrica capped account.
Last time I had a 4Mbit line I remember it going over 3.50Mbps - any ideas on this?

Thanks,
Psy
 
G.DMT <8Mbp/s
ADSL2+ >8Mbp/s

Post line statistics that are found in your router IE Sync rate and noise margin.
 
I'm no expert, but I think ADSL 2+ is newer tech for 20 Mbps lines. Might be more stable if you have problems.

I'm on a 2 Mbps line and max speed is about 1,7. So 3,5 on a 4 meg line is the max that you will get.

Cheers
 
Tested with router GMT got 8 mb adsl2+ back to 20mb for me.
 
If you guys are looking for info on G.DMT and the different modes, then have a look at the following links:
Line Mode: G.DMT Mode, ADSL2+ Mode? - Earthlink DSL | DSLReports Forums
G.992.1 - Wikipedia, the free encyclopedia

In short:
G.DMT mode can do up to 8Mbps.
G.dmt.bis is also known as ADSL2
G.dmt.bis+ is also known as ADSL2+

If you're further than ~2.5km away from the DSLAM, then switching to ADSL2+ or VDSL won't really give you a noticeable download speed increase either.

The technical reason why:
ADSL2+ and VDSL uses more (and higher) frequency bands than G.DMT, which allow them to transfer more data, BUT the higher frequencies also degrade faster in quality over the same distance than lower frequencies.
 
Last edited:
Sorry, was busy catching up on some quality internet time last night so didn't want to switch modes and wait for it to sync and spend time posting line stats on the different modes.

I will do that today when I get home though. I spoke to the Telkom technician when he came to install the telephone line and says the exchange is extremely close to my house and I should be able to get 20 or 40Mbit ADSL without any issues.
 
Chevron said:
That's impossible. Pics or gtfo.

Telkom doesn't use G.dmt for anything above 6MB/s in SA.
Click to expand...


I'm only synced at 4096 but my router says I can connect up to 11343 down and 1123 up, on G.DMT, but the back haul link to these old exchanges is to low to give people more than 4096, that's probably why telkom will not up it more than 6Mb.
 
Also, if your upload speed is not syncing at full 512 then it 99% of the time it means your mode is wrong, that's why when you changed to G.DMT it's syncing at 512. The profile mode on Telkom's side is only G.DMT, exchange does not support ADSL2+

What you can do is phone telkom to see if they can change it on there side, if they can't the exchange does not support it.

This is my options I have, only up to 4096, but only on G.DMT as my exchange does not support ADSL2+

(See the DSL Sync Mode option, that's on Telkom's side, they need to make the changes there, this is a screenshot of their system)
ADSL.jpg
 
Last edited:
So here we go.

Router set to ADSL G.DMT

SNR Margin (Upstream) 12.0 db
SNR Margin (Downstream) 22.0 db
Line Attenuation (Upstream) 10.5 db
Line Attenuation (Downstream) 26.0 db

Router set to ADSL 2+

SNR Margin (Upstream) 16.0 db
SNR Margin (Downstream) 37.6 db
Line Attenuation (Upstream) 10.4 db
Line Attenuation (Downstream) 15.6 db


Seems I get better stats with ADSL2+ ? So I guess that is what I shall have it set to.
 
Last edited:
Yeah I did a quick test to see what's up. I got a 10Mbps line.

Router set to ADSL G.DMT

adsl_gdmt.png


Router set to ADSL 2+

adsl_adsl2.png
 
Interesting, yours seems to be the other way around but then there is the line sync speed difference.
 
Yeah I see the stats and attainable rate is better on adsl2+ mode. G. DMT has a limit of 8Mbps anyways but the line stats are still bad when I switch to that mode. The errors also increased.
 
Would there be a reason why my router cant connect to G.DMT anymore, my line will only sync when ADSL2+ is selected?
 
Willy2580 said:
Would there be a reason why my router cant connect to G.DMT anymore, my line will only sync when ADSL2+ is selected?
Click to expand...

Weird, what speed line do you have?
Unless some other settings are incorrect. Although it seems you'd generally prefer to use ADSL2+ if it is supported?
 
Willy2580 said:
Would there be a reason why my router cant connect to G.DMT anymore, my line will only sync when ADSL2+ is selected?
Click to expand...

Could be that you're connected to a DSLAM that only supports ADSL2+

PsyCLown said:
Weird, what speed line do you have?
Unless some other settings are incorrect. Although it seems you'd generally prefer to use ADSL2+ if it is supported?
Click to expand...

ADSL2+ will always be better than ADSL (G.DMT) unless you are right on the edge, distance wise, for ADSL
 
You must log in or register to reply here.
Back
Top
Sign up to the MyBroadband newsletter
X