Over the past couple of weeks we have seen FTTC lines drop and reconnect with in increase in latency of around 15ms. This is seen on the monitoring graphs as a thicker blue line.
Upon first glance it looks as if interleaving has been enabled, but a line test shows that this is not the case.
We've been in contact with BT and it does look like BT are rolling out a new profile on to their Huawei DSLAMs in the local green cabinets. It has been expected that BT would be rolling out this new profile, but we didn't expect such an increase in latency.
The profile adds 'Physical Retransmission (ReTX) technology (G.INP / ITU G.998.4)' which helps with spikes of electromagnetic interference and can make lines more stable.
We would hope to have control over the enabling and disabling of this profile, but we don't. Line profiles with FTTC is managed by BT Openreach and are tricky for us and even BT Wholesale to get adjusted.
We're still discussing this with BT and will update this post with news as we have it.
This has been escalated to the head of fibre deployment within BT Wholesale and we are expecting an update by the end of the day.
Further information about G.INP: http://www.ispreview.co.uk/index.php/2015/01/bt-enables-physical-retransmission-g-inp-fttc-broadband-lines.html http://www.thinkbroadband.com/news/6789-impulse-noise-protection-rolling-out-on-openreach-vdsl2.html http://forum.kitz.co.uk/index.php?topic=15099.0 ...among others.
BT have asked us for further information which we have provided to them, we don't expect an update now until Monday
This is still ongoing with BT Wholesale and BT Openreach.
This has been escalated to a very senior level within BT and we are expecting a proper update in the next few days.
We have just received the below back from BT on this Following communications from a small number of BTWholesale FTTC comms providers regarding Openreach’s implementation of Retransmission and the identification of some your customers who have seen increased latency on some lines for some applications since retransmission was applied. Over the last 4 weeks I have been pushing Openreach to investigate, feedback and provide answers and options related to this issue. As a result attached is a copy of a briefing from Openreach; sent to their CPs today, on how RetX works and what may have caused this increase latency. This info is being briefed to all BTWholesale customers via our briefing on Saturday morning 25/4/15 but as you have contacted me direct I’m sending this direct as well as providing ann opportunity to participate in a trial. Openreach have also advise me this afternoon that they intend to run a trial next week (w/c 25/4/15) on a small set of lines; where devices aren’t retransmission compatible in the upstream to see if changing certain parameters removes the latency and maintains the other benefits of retransmission. The exact date lines will be trialled has yet to be confirmed. However, they have asked if I have any end users who would like to be included in this trail. To that end if you have particular lines you’d like to participate in this trial please can you provide the DN for the service by 17:00 on Monday 28th April so I can get them included. This is a trial of a solution and should improve latency performance but there is a risk that there may be changes to the headline rate.
Update to Trial here: https://aastatus.net/2127