Supply WBC that has SRA

[#1]

It is coming to light that BT have decided to not enable SRA (Seamless Rate Adaption) as a part of ADSL2+ on WBC connections.
This is a big oversight, I have heard the 'reasons' from DaveT, etc. The so called benefits of not enabling SRA and needing BRAS like profiling are at best described as dubious when WBC has become a purely IP network compared to the ATM based legacy parts of the network we had with IPStream/MaxDSL.
So can PN offer an ADSL2+ connection with SRA enabled without BRAS or PN throttling the connection, (no need right ... because IP has flow control right?) for those like me on long lines, the benefits are real.

SW.

[#2]

Where did you hear this SW?

[#3]

Both here in the '21CN Trial' section of this Forum and over on TBB Forums.
SW.

[#4]

Well the good news is now that it seems all the non-BTW suppliers in those nicely competitive Market3 exchanges are all WITH SAR and WITHOUT the BRAS/profile nonsense, the sync speed is your connection speed and IP packet flow control does the rest.
Looks like BTW is the very odd one out ...

[#5]

Are you sure this information is substantiated, if it is supposedly so what authoritative source did it come from and has it been posted / published in an authoritative place? Also a link to the TBB source may come in handy.

[#6]

Quote

Presently the only ISP in the UK that supports SRA is UKOnline on their adsl 2+ LLU exchanges.

See http://www.kitz.co.uk/adsl/adsl_technology.htm#SRA

[#7]

It seems that O2/Be also have it, but that is based purely on some comments from comments in forums.

[#8]

Can I ask a silly question as I have been searching the internet and can't find an answer.
If SRA is employed where does the buffering take place? For example if the speed from the DSLAM/MSAN is reduced does the BT equipment do the buffering?

[#9]

Quote from: itsme

If SRA is employed where does the buffering take place?

At the same point it currently does, IP packets have flow control.
SW.

[#10]

And where is that point?

[#11]

At the originator of the data.

[#12]

So what is different with SRA to stop the below happening under the BRA system.

Quote

Data Rate (bRAS profile) The Data Rate is the fastest speed (throughput) that you will be able to download at and is profiled by BT at the bRAS. A maximum throughput level is needed to stop more data than your line can physically achieve being sent down the backhaul and being dropped at the DSLAM.

[#13]

On 20CN connections to the exchange, there are parts of the network that are still 'frame based' which is a historic issue from the days when BT supplied a voice network. BT claim that BRAS was needed due to the issue you quoted below. There is much speculation if this is truly necessary, however that is the BT stance on the subject.
On a 21CN connection, the connection is all IP based, there is no part of the network which is frame based, hence that problem just does not happen.
SW.