Monday, 23 March 2015

"SDH bypass" works - does this mean no chance of ADSL2+?

[edit 25-1-16 the fibre for the new cabinet in the village comes up from Oban, rather than from the Ledaig exchange itself, therefore the exchange has not yet been upgraded to 21CN  and ADSL2+ is not an option at present]

BT have scheduled work at the Ledaig exchange for "SDH bypass, programme number 46, migrating customers to a strategic transport platform" on 1st April 2015 overnight. 

I *think* this means that the possibility of non-FTTC connections at Ledaig being co-incidentally upgraded to ADSL2+ is now dead in the water. 

What I *think* is happening, in simple terms, is that the existing ADSLMax circuits that use an old 'backhaul' for transferring the data from the exchange onto the rest of the internet, are being altered slightly to use a new 'backhaul' that is common with the new FTTC connections. The kit in the exchange where your copper line terminates  - the "DSLAM" - will remain the same; data from the DSLAM will just be transported on from the exchange to the rest of the internet using a different communication technology. 

This effectively extends the life of the existing ADSLMax (8Mbps) broadband DSLAMs as their traffic can be ported over the new 21CN, BT can then retire the old 20CN backhaul from the exchange without the need to convert each customer to a new ADSL2+ MSAN.

This means your connection to the exchange will still be "ADSLMax" (the 8Mbps broadband) product, and therefore your internet connection speed will remain the same. I had hoped that as part of the exchange works, the DSLAMs would be replaced by "MSAN"s which will use the new 21CN backhaul and give you "up to 24Mbps" broadband connections instead. However, BT will be performing an 'SDH bypass' instead, to route these ADSLMax connections out from the exchange over the 21CN network, without migrating end users to ADSL2+ instead.

I will admit to not fully understanding the terminology. I have found this publication on the internet from BTwholesale that shows a diagram of what will change:

Page 43 describes how existing products 'outside the WBC footprint' will route traffic direct from the DSLAM to the BRAS, via SDH backhaul.

BT still plans to retire the old "20CN" network, of which these old MAXDSL connections are part, but for Ledaig, by performing this 'SDH bypass', BT can extend the life of ADSLMax connections from the home to the exchange, whilst the backhaul of data can be ported over the (new) 21CN link, which is now at the exchange and will be used by the FTTC connections.

No comments:

Post a Comment