Wednesday, 30 July 2014

good graphic illustrating ADSL ADSL2+ and FTTC

here's a good graphic for the difference between ADSL (existing Benderloch broadband), FTTC ('superfast broadband') and ADSL2+ (the possible improvement that exchange-only lines might be able to benefit from)

Existing ADSL broadband

Your home phone line copper wires terminate in the exchange at a "DSLAM", and your home modem communicates with this DSLAM using a protocol called "ADSL" (or ADSLMax,  ADSL 1)
Data is sent from the exchange over BT's "20th Century" network to a BT Core Node, and then (effectively) on to the rest of the internet

New FTTC superfast broadband where available

Your phone line copper goes from your house to a streetside cabinet. From here,  copper wire still goes all the way to the exchange for your voice(telephone) service, but a short jumper cable is added from the street cabinet to a new "FTTC"  cabinet next to it, which contains a new  "VDSL2 DSLAM" bit of kit and this is the path your new superfast broadband takes.
A fibre optic cable takes the data from this new cabinet DSLAM back to the exchange.
In the exchange, the fibre is terminated at an "Optical Line Termination" point (not shown below) and connected to a Layer 2 Switch (L2S), from where it passes via the newly installed 21CN connection to the BT Core node and onto the rest of the internet (effectively)

Possible New ADSL2+ access for exchange-only lines and non-FTTC connections at Ledaig

Your home phone line copper wires terminate in the exchange at a new MSAN in the exchange (this is what I don't understand - whether  MSANs is going to be installed at the Ledaig exchange as part of the upgrade to 21CN at the exchange or not).
Your home broadband modem communicates with this MSAN using a protocol called "ADSL2+".

Data passes from the MSAN to BT's Core Node (and onto the rest of the internet effectively) via BT's 21CN network.
(not shown is that your voice(telephone) can also terminate at this MSAN and your voice calls transferred over the 21CN network too - meaning that the old 20CN equipment can be retired from the exchange)

You can see that FTTC uses the new 21CN network to transfer data from the exchange on to the rest of the internet, as does ADSL2+. 
So my question is whether the addition of 21CN at the exchange means ADSL2+ becomes available at the exchange too, or whether they won't bother installing the MSANs for ADSL2+ (and voice) and just leave existing ADSL connections on the 20CN.

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