IP Stream Max: This is the BT service on which Zen 8000 Pro and Active are based. It allows for downstream line rates of up to 8192kbps, and upstream line rates of up to 448kbps.
Line rate: Line rate, or synchronisation(sync) speed is the speed at which your ADSL router or modem communicates with the BT Exchange. This is always higher than the speed data will actually be downloaded or uploaded when you use the connection.
Data rate: Data rate, or throughput, refers to the speed at which you are able to download and upload information from Web sites or other services on the Internet.
Rate Adaptive: IP Stream Max is referred to as a 'Rate Adaptive' service - this means the service will change the line rate based upon line conditions, which can vary over time. Due to fluctuations in line quality a line could Rate Adapt from a higher speed during the day to a lower speed at night.
Interleaving: Interleaving provides error correction on lines. It is used to stabilise a line at higher speeds by providing additional information which is used to fix problems caused by errors occurring on the line. Interleaving can result in higher latency (pings), which could affect game play if latency on a line is high prior to switching to the Pro or Active services. Interleaving is automatically applied if BT's Dynamic Line Management systems determine it is necessary to maintain a higher speed connection. An option is available to disable it if it affects the customer's ability to play games and use other latency-sensitive applications. Further details on how this can be done are available in the article "Changing the Interleaving option on Zen 8000 Pro/Active" under Related Articles.
Fast Mode: This is the default mode of the Pro and Active services if interleaving is not required to stabilise the line.
Dynamic Line Management: Dynamic Line Management (or DLM) is a collective term for the systems used by BT to stabilise an IP Stream Max service. It automatically logs information on a line's performance and takes steps to stabilise the line. It can do this by applying Interleaving, and/or reducing the maximum speed a line can connect at. DLM should result in a stable service being established over the first three days after receiving the Pro or Active service.
NOTE: DLM uses information on disconnections and reconnections (where the line is dropped, and a new line rate established) to determine what steps are required. Frequent reboots of ADSL router/modems could be interpreted by DLM as a line problem, so measures could be taken to reduce the line rate permitted.
Maximum Stable Rate: The Maximum Stable rate (or MSR) is a line rate threshold established by BT over the first 10 days of service on Pro and Active. It is used to determine when a drop in line rate would be considered a fault. Once an MSR is established BT will accept a fault report if the line rate drops by 30% or more. e.g. if the MSR established is 8192kbps a fault can be reported when the line rate drops to 5734kbps or less.
NOTE: An MSR is only established after a connection has been established for a total of 10 days. If you power down your ADSL equipment it may take longer to establish an MSR, and faults may only be reported if the line rate drops below 288kbps.
Broadband Remote Access Server Profile: The Broadband Remote Access Server Profile (or BRAS Profile) is responsible for regulating the maximum data rate you will receive on IP Stream Max services. This is initially set to 2Mbit/s (if the line rate achieves is above 2172kbps), but will rise if your line can support higher speeds than this. Initial rises should occur within 75 minutes of you receiving your Pro or Active Service, however a BRAS Profile may take up to three days to increase as the profile only changes when a stable connection has been maintained for a period of time. If DLM changes are taking place this time could be extended. This allows BT to monitor the line's performance and ensure the new line rate is maintained. The BRAS Profile could also drop if the line rate decreasing significantly - when this occurs a further period will be required for it to rise again.
NOTE: If your initial BRAS Profile does not rise above 2Mbit/s after 75 minutes, despite maintaining a high line rate, you should power down your ADSL equipment for at least 30 minutes before powering back up. This may prompt BT to begin the 75 minute BRAS Profile training period again if your new line rate differs from what was originally established after your regrade.
Contention: ADSL products are provided over a shared platform, subject to contention. This means during busy periods the throughput experienced could be below the maximum possible at quieter times of the day. BT publish a chart of performance thresholds which provide an indication of the worst/best case experience on IP Stream Max services:
Line Rate Performance Threshold
from 288Kbit/s to 576Kbit/s 50-500kbit/s
from 576Kbit/s to 1152Kbit/s 100-1000kbit/s
from 1152Kbit/s to 2272Kbit/s 200-2000kbit/s
from 2272Kbit/s to 8128Kbit/s 400-7150kbit/s