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Zen's 8000 Services Glossary

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Zen's 8000 Services Glossary


Zen 8000 Services Glossary

Aim of this article:

This article provides a glossary of terms related to Zen 8000 services, and the underlying technology on which these products are based - IPStream Max and IPStream Max Premium (DSL Max).

Glossary of terms:

IP Stream Max: This is the BT service on which Zen 8000 Pro, Active and Lite are based.  It allows for downstream line rates of up to 8192kbps, and upstream line rates of up to 448kbps.

IP Stream Max Premium: This is the BT service on which Zen Office 8000 and Zen Office 8000 Max are based.  It allows for downstream line rates of up to 8192kbps, and upstream line rates of up to 832kbps.

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: IPStream Max/Max Premium are referred to as a 'Rate Adaptive' services - 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 8000 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 services" 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 IPStream Max/Max Premium services.  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 8000 service.  During this training period disconnections may be experienced when changes in line speeds occur.
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 the 8000 services.  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 20% 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 period of at least 15 minutes.  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.

Maximum Stable Rate Reset: If the line quality has changed since the MSR was set you can request the line MSR (and FTR) be reset, this will restart the 10 day training period, this will have no impact on the speed of your service and does not guarantee the MSR will increase.  If the line quality has deteriorated it is possible that a lower MSR may be set after the reset, this will make it harder to raise a fault based on the FTR (Fault Threshold Rate).

Fault Threshold Rate: 
The fault threshold rate (or FTR) is 80% of the MSR.  If the line rate drops below the FTR for more than 8 hours in a week period it is considered a fault and a low threshold breach fault can be raised. 

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 IPStream Max/Max Premium 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.  If your line performs significantly better than 2Mbit/s then initial changes should take place within 48 hours.  If your line is only marginally better than 2Mbit/s then any increase in speed could take up to five ful days.

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 IPStream Max (Zen 8000 Pro, Activeand Lite) and IPStream Max Premium (Zen Office 8000 Max) services:

IPStream Max (Zen 8000 Pro, Active and Lite):

Line Rate Performance Threshold
288Kbit/s 50-250kbit/s
from 288Kbit/s to 576Kbit/s 50-500kbit/s
from 576Kbit/s to 1152Kbit/s 200-1000kbit/s
from 1152Kbit/s to 2272Kbit/s 400-2000kbit/s
from 2272Kbit/s to 8128Kbit/s 600-7150kbit/s

IPStream Max Premium (Zen Office 8000 and Zen Office 8000 Max):

Line Rate Performance Threshold
288Kbit/s 100-250kbit/s
from 288Kbit/s to 576Kbit/s 100-500kbit/s
from 576Kbit/s to 1152Kbit/s 400-1000kbit/s
from 1152Kbit/s to 2272Kbit/s 800-2000kbit/s
from 2272Kbit/s to 8128Kbit/s 1200-7150kbit/s



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