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Posts: 3,140
Registered: ‎22-05-2012

Technical Glossary

Technical Glossary:

 

Table of Contents:

Click on one of the terms below to jump to that term definition:

 

  1. #Sync Rate or Connection Speed.
  2. #Digital Subscriber Line Access Multiplexer (DSLAM).
  3. #Sync or Synchronisation.
  4. #Modem.
  5. #Router.
  6. #BT HomeHub 1 to 2.
  7. #BT HomeHub 3 to 4.
  8. #BT HomeHub 5.
  9. #Throughput speed.
  10. #Bits Vs Bytes.
  11. #IP Profile.
  12. #Asymmetric Digital Subscriber Line (ADSL).
  13. #ADSLMax line modulation.
  14. #ADSL2/2+ line modulation.
  15. #Interleaved Latency type.
  16. #Fastpath Latency type.
  17. #Line Attenuation.
  18. #Dynamic Line Management (DLM).
  19. #Noise Margin or Signal to Noise Ratio Margin (SNRM).
  20. #FTTC – Fibre to the Cabinet.
  21. #BT Unlimited Faster Broadband.
  22. #FTTP – Fibre to the Premises.
  23. #FTTPoD – Fibre to the Premises on Demand.

 

 

 

Sync Rate or Connection Speed – The speed in which your HomeHub/Modem has synchronised, negotiated, with the exchange equipment or the DSLAM (Digital Subscriber Line Access Multiplexer) in the FTTC cabinet for FTTC connections. The figure will usually be in megabits per second (Mbps) or kilobits per second (Kbps) and is very much dependent on “copper” line distance from the exchange to the property for ADSL broadband or the line distance from the FTTC DSLAM cabinet for FTTC broadband.

However in both cases the “copper” line quality is also an important factor.

 

Digital Subscriber Line Access Multiplexer (DSLAM) - A network device, located in the exchange for ADSL connections or in the FTTC DSLAM street side cabinets for FTTC connections, which connects multiple customers to a Digital Subscriber Line service and the rest of the Internet Service Provider's network.

 

Sync or Synchronisation - The talking/negotiation between the exchange equipment or DSLAM and your HomeHub/Modem to initialise a connection.

 

Modem – The device encodes digital information and demodulates signals to decode the transmitted information to and from the exchange.

 

Router – A device that allows multiple devices such as computers, mobile devices, and other networking devices to use a single broadband/internet connection.

 

BT HomeHub 1 to 2 – A BT Retail (Consumer) Modem-Router for ADSL lines. These Modem-Router are no longer being manufactured. They don't support VDSL (FTTC) connections.

 

BT HomeHub 3 to 4 – A BT Retail (Consumer) Modem-Router for ADSL lines, which also supports BT Retail's Fibre broadband services (FTTC & FTTP) via the WAN (Wide Area Network) Port when connected to a VDSL (for FTTC) modem or a ONT (Optical Network Terminal) Unit for FTTP.

 

BT HomeHub 5 – A BT Retail (Consumer) Modem-Router for both ADSL lines and VDSLx (FTTC) lines without requiring a separate modem for VDSL. It also supports a connection through the WAN (Wide Area Network) Port when connected to a VDSL (for FTTC) modem or a ONT (Optical Network Terminal) Unit for FTTP.

 

Throughput speed - This is the speed variable which speedtest applications measure (eg http://speedtest.btwholesale.com/ ). The throughput speed can be affected by a number of factors such as Wireless  interference, if you are connected via Wireless or Ethernet, the number of devices sharing the available bandwidth, congestion external or within BT Wholesale’s network, plus more.

It is always recommended to perform a speedtest with a wired Ethernet connection. This is usually measured in Megabits per Second (Mbps) or Kilobits per Second (Kbps).

 

Bits Vs Bytes. -  When you run a speedtest,  for example http://speedtest.btwholesale.com/ , the results will usually be in Megabits per Second (Mbps). However when you download/transfer a file or program you will notice the Transfer rate will be in Megabytes per Second (MBps).

So if you have a download throughput speed of ~56 Mbps then a transfer rate of 7 Megabytes per Second (MBps) is the same as saying 56 Megabits per Second (Mbps).

 

The same applies for Kilobits per Second (Kbps) and Kilobytes per Second (KBps).

Easy way to remember is that there are 8Bits in 1 Byte.

 

IP Profile – an IP profile (or 'BRAS profile') is a speed limit applied to your broadband service by the local exchange. Its purpose is to ensure the exchange doesn't 'overload' your broadband service by sending more data down your phone line than it (or your BT Home Hub, router or modem) can physically handle.

  • If you are on the BT Wholesale 20cn network on ADSLMax then the IP Profile is set from band parameters based upon your sync rate.
  • For those on the 21cn network (be that still on ADSLMax or ADSL2/2+) the IP Profile is 88.2% of your sync rate.

 

More information regarding IP Profiles can be found at http://bt.custhelp.com/app/answers/detail/a_id/9760/~/what-is-my-broadband-%27ip-profile%27-and-why-...

 

Asymmetric Digital Subscriber Line (ADSL) – A type of Digital Subscriber Line technology that enables faster data transmission over conventional "copper" lines compared to dial-up and Symmetric Digital Subscriber Line (SDSL) services. ADSL has a greater downstream bandwidth compared to its upstream bandwidth.

 

ADSLMax line modulation – Uses the ITU G.992.1 (G.DMT) line modulation and for a residential line supports a downstream sync rate of up to 8Mbps and an upstream sync rate of up to 448Kbps.

 

ADSL2/2+ line modulation –  Uses the ITU G.992.3 line modulation standard for ADSL2, which supports a downstream sync rate of up to 12Mbps and an upstream sync rate of up to 1.2Mbps.

For ADSL2+ the line modulation standard is ITU G.992.5 and supports a downstream sync rate of up to 24Mbps (only if you are very, very close to the exchange however) and an upstream sync rate of up to 1.2Mbps.

Though in both situations the upstream speed is usual around 0.8Mbps.

 

Interleaved Latency type – Uses error correction algorithms to improves broadband speed and stability on long or noisy phone lines. Though latency/ping will increase slightly.

More information regarding Interleaved Latency type can be found at http://bt.custhelp.com/app/answers/detail/a_id/8547/~/what-is-interleaving%3F-what-are-its-pros-and-...

 

Fastpath Latency type – Hardly any error connection is used, however this can cause lots of errors to increase with long or noisy phone lines.

 

Line Attenuation – A variable that is calculated for both downstream and upstream connections by the modem/Homehub which represents the length and resistance in a “copper” line. The higher the number the longer the line is or the higher the resistance is. Some modems only go upto 63.5dB however the line attenuation may be higher. The unit is in decibels (dB).

 

Dynamic Line Management (DLM) – An automated system that monitors the errors and disconnections on broadband connections. The DLM automatically controls the Latency type, Noise margin, Sync rate, IP Profile and Line modulation depending on the quality, length and status of your line.

 

Noise Margin or Signal to Noise Ratio Margin (SNRM) – A variable measured in decibels (dB) that represents the Signal strength to level of noise on the line. BT Retail's (Consumer) default target noise margin is around 6dB, however if the DLM thinks your line is stable enough and in good quality then the DLM may decrease this target to 3dB.

 

FTTC – Fibre to the Cabinet – A fibre based broadband solution where a FTTC DSLAM cabinet is installed and linked to the original telephone cabinet (PCP). If you are subscribed to a FTTC broadband service such as BT Infinity or BT Unlimited Faster Broadband then your broadband connection travels from the exchange to the FTTC DSLAM cabinet via a fibre cable then from the FTTC DSLAM and PCP to your property via the existing “copper” cable.

The current speed achievable is upto 80Mbps downstream and upto 20Mbps upstream, however this depends on what service level you are on and your distance from your DSLAM cabinet as well as line quality.

 

BT Unlimited Faster Broadband – This is BT Retail's (Consumer) FTTC broadband service for those who are estimated 15Mbps or less on FTTC.

For more information on BT's Unlimited Faster Broadband go to http://bt.custhelp.com/app/answers/detail/a_id/47740/~/what-is-unlimited-faster-broadband%3F

 

FTTP – Fibre to the Premises – A fibre broadband solution where the connection between your property and the exchange is entirely over a fibre

The current speed achievable is upto 300Mbps downstream and upto 30Mbps upstream, however this depends on what service level you are on.

 

FTTPoD – Fibre to the Premises on Demand – This is a service provided by Openreach where an end user can pay to have a FTTP fibre connection all the way to their property. However you need to be on FTTC enabled cabinet that has FTTPoD as an available service.

Please be aware that BT Retail Residential (Consumer) do not currently have FTTPoD as an available broadband service, though may be able to be provided through BT Business.

 

FTTP – Fibre to the Premises – A fibre broadband solution where the connection between your property and the exchange is entirely over a fibre

The current speed achievable is upto 300Mbps downstream and upto 30Mbps upstream, however this depends on what service level you are on.

 

FTTPoD – Fibre to the Premises on Demand – This is a service provided by Openreach where an end user can pay to have a FTTP fibre connection all the way to their property. However you need to be on FTTC enabled cabinet that has FTTPoD as an available service.

Please be aware that BT Retail Residential (Consumer) do not currently have FTTPoD as an available broadband service, though may be able to be provided through BT Business.

 


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