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ADSL2+ Rate Adaption

VileReynard
All Star
Posts: 11,200
Thanks: 307
Fixes: 11
Registered: ‎01-09-2007

ADSL2+ Rate Adaption

How does ADSL2+ rate adaption work?
Will there still be the daft "wait 3 days and see if it gets better"?
How closely will the data rate correspond to the sync rate?
Will there be a fixed "noise margin" required?
Every few weeks my line seems to hit a small event which causes it to lose 2-3 Mbps on the BRAS profile for 3 days.
Hopefully, I will get a training period when ADSL2+ starts.

9 REPLIES
ctech500
Grafter
Posts: 255
Registered: ‎06-08-2007

Re: ADSL2+ Rate Adaption


Seamless Rate Adaptation (SRA)
SRA allows modems to make seamless data transfer rate changes to avoid dropping a connection. Modems are affected by cross talk from adjacent lines, as well as by other interference such as temperature changes and radio signals. Any interference on the connection can cause a modem to retrain on another connection and drop the existing connection. SRA makes dynamic data transfer rate changes to accommodate temporary noise conditions on the line thus preventing dropped connections.

As far as I am aware  BT21CN dose not deploy SRA (Seamless Rate Date) from what I have read in other threads 21CN will use the same BRAS profiling system but it will be more "intelligent"  then the current solution.
It would be interesting to know why SRA is not being used 21CN
VileReynard
All Star
Posts: 11,200
Thanks: 307
Fixes: 11
Registered: ‎01-09-2007

Re: ADSL2+ Rate Adaption

I can remember when "modem negotiation" was the latest thing in modems - with fall forward / fall back.
It applied AFAIK from the time of 9,600bps modems - so SRA ain't exactly aa new thing.

Community Veteran
Posts: 3,366
Thanks: 15
Registered: ‎06-04-2007

Re: ADSL2+ Rate Adaption

Is anybody now connecting on WBC/21CN now seeing the SRA in action at all?
SW.
--
3Mb FTTC
https://portal.plus.net/my.html?action=data_transfer_speed
James
Grafter
Posts: 21,036
Registered: ‎04-04-2007

Re: ADSL2+ Rate Adaption

It's the first day, give it time Smiley
ctech500
Grafter
Posts: 255
Registered: ‎06-08-2007

Re: ADSL2+ Rate Adaption

I'm a little confused here
Is BRAS still being used on 21CN ?
Could there be some sort of "hybrid" BRAS/SRA  solution going on here.
My understanding was the 21CN would introduce a more "Intelligent" BRAS which is not SRA or is it? Wink Undecided
James
Grafter
Posts: 21,036
Registered: ‎04-04-2007

Re: ADSL2+ Rate Adaption

bRAS is still being used on ADSL2+ on the BT implementation.  However, it's a more intelligent form.
This should hopefully mean better.
pnf
Grafter
Posts: 266
Registered: ‎07-11-2007

Re: ADSL2+ Rate Adaption

Info from router log:  (After reboot to increase IP profile):
Info 00:01:07 (since last boot) PPP CHAP Receive challenge (rhost = THN-AG2)
Info 00:01:06 (since last boot) PPP CHAP Receive challenge (rhost = bras-red5.bm-th)
Community Veteran
Posts: 3,366
Thanks: 15
Registered: ‎06-04-2007

Re: ADSL2+ Rate Adaption

Has anybody yet been running RouterStats to see if there is any sign of the Seamless Rate Adaptation happening?
SW.
--
3Mb FTTC
https://portal.plus.net/my.html?action=data_transfer_speed
VileReynard
All Star
Posts: 11,200
Thanks: 307
Fixes: 11
Registered: ‎01-09-2007

Re: ADSL2+ Rate Adaption

I have - it's pretty good - rate adaption hardly interferes at all.
I've had phone line problems (engineer visited):-

(Ignore the vertical lines - they indicate that RouterStats failed to make a connection with the router).
The magenta line is a moving average - the blue lines indicate actual speed achieved.
I'm for future improvements...  Smiley