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Another Max product update
Monday 10 April 2006 18:49:00 by Andrew Ferguson

Following on from the update on Friday 7th April, we have more information for those wanting to know what is happening with the Max products.

Concerning the ongoing problems with the Data Rate staying fixed at a lot lower speed than the line sync speed, it is emerging that if your ADSL modem is re-connecting at the same or similar line sync speeds this may not always trigger an update event to occur in the BT Wholesale systems. The upshot of this is that the people whose line is very good and can sync at 8128kbps, are stuck with waiting for the three day BRAS profile updating event to occur. If after the three days your line is still giving 2Mbps performance and it is syncing at much faster rates then it is time to contact your provider. We should add that if you previously heavily tweaked your computers connection, you may need to do the tweaking again to get the full effects of the extra speed.

We also have some information that will mainly concern those with a line that syncs at the lower speeds, and very much concerns those with a 0.5Mbps service hoping to squeeze some more speed out of their line. The BRAS rate limiting which sets the maximum IP rate your line can sustain has very few steps available below the 2Mbps line sync speed. A page detailing the available Data Rates can be found on the website.

ATM Line sync speed

IP Data Rate

from 288Kbps 0.25Mbps
from 576Kbps 0.5Mbps
from 1152Kbps 1Mbps
from 1728Kbps 1.5Mbps
from 2272Kbps 2Mbps
from 2848Kbps 2.5Mbps
from 3424Kbps 3Mbps
from 4000Kbps 3.5Mbps
from 4544Kbps 4Mbps
from 5120Kbps 4.5Mbps
from 5696Kbps 5Mbps
from 6240Kbps 5.5Mbps
from 6816Kbps 6Mbps
7392Kbps 6.5Mbps
7968Kbps 7Mbps
8128Kbps 7.15Mbps

To give an example from the table, if you have a downstream line sync speed of 768Kbps, the maximum throughput of data at the IP level will be 0.5Mbps, in other words identical to what you get on a Home/Office 500 service. The only benefit for that user would be the increased upstream offered by the Max products. The large step sizes are what is most likely behind the decision by BT Retail to not offer upgrades to its customers on very long lines, since they felt some may see little benefit. The lack of more steps at lower speeds is something that should be looked into we feel. While the majority of lines will manage a line sync speed in excess of 2272Kbps, there are plenty of lines that will only run in the 576Kbps to 2000Kbps type range, and to only offer Data rates of 0.5Mbps, 1Mbps and 1.5Mbps seems odd. A step size of 128Kbps in the Data Rate for lines syncing under 2272Kbps would be welcomed.

Another table of data is the one showing the performance thresholds that BT Wholesale expect on their services, (copied from here).

Line Sync Speed

Performance Threshold

up to 287Kbps 50 - 250Kbps
up to 575Kbps 50 - 500Kbps
up to 1151Kbps 100 - 1000Kbps
up to 2271Kbps 200 to 2000Kbps
up to 8127Kbps 400 to 7150Kbps

The maximum figures represents the highest burst speed BT Wholesale expect people to see at the quieter times of day, and generally the traffic priorities from the exchanges to the service providers are managed such that at the busier times you should not see lower than the low figure. It is possible to get speeds slower than those quoted, and if these are present over say a 24 hour period you should be able to get this investigated by your service provider. At the busier times those with an Office or Premium Max connection will receive a higher priority, and thus should feel any congestion to a lesser extent. Systems are in place that should not see any single user starved of bandwidth in the worst case scenario, in these scenarios some bandwidth is reserved for all customers, thus avoiding a few high speed users stopping others from working totally.

Update 9pm 10th April: Performance threshold table correction, line speeds were incorrect.


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