ADSL downstream speed dropped by more than 50%

[#1]

Hi,

Over the last 3-4 weeks, the downstream bandwidth of our PlusNet ADSL line has dropped from 11 Mbps down to about 5Mbps.  When we first noticed the reduction, the bandwidth was down at around 6Mbps and the problem seems to be getting progressively worse since.  It is now getting to the point where it is beginning to adversely affect the ability of my wife and I to both work from home at the same time.

I have attached a comparison of the line stats reported by the router yesterday, compared to those from about 4 months ago and it is particularly noticeable that the SNR has changed significantly and the path mode has changed.  No configuration changes have been made to the router in the intervening period.  The upstream speed has also dropped, but only by about 10%, which has been confirmed by running speed tests. 

We first noticed the reduction in speed shortly after some wet and windy weather, which prompted me to wonder if the problem has been caused by damage to the overhead cables somewhere between our house and the exchange.  With this is mind, I have gone through the following diagnostic ritual:

1. Power cycle the router.  No change in speed.
2. Silence test with a phone connected directly into the master socket internal socket.  There is a degree of white noise on the line, but otherwise it seems quiet.
3. Ran a speed test with the router connected directly into the master socket internal socket.  The test reported about a ~1Mbps improvement, but still nothing close to the 11Mbps that was consistently being attained a month or so ago.
4. Replaced the line filter connecting the router into the master socket, to eliminate that as a possible cause.  This had negligible effect on the line stats or speed.

These results suggest that the problem is not in equipment on the consumer side of the master socket.  Are there any checks that can be done from the Plusnet end which might throw more light on the cause of the problem, please?

Kind regards,

Simon

[#2]

Together with our network partners at Openreach we will try to provide you with the best speeds possible. If you feel this is not the case, please raise your speed fault online at faults.plus.net

[#3]

Hi @Gandalf,

Thank you for the reply.  I think an abrupt drop of 50% in downstream speed is worthy of some further investigation so I will raise a ticket.  We have had another anomaly this morning where there was a period when the link seemed to be dropping a lot of packets to the extent that we could barely send and receive email.  Packet loss is highly unusual for our link, even since the line speed dropped, which suggests something, somewhere isn't quite right.  Fortunately, it cleared after a few hours. 

I have finally found and configured another router, so I'll connect that for a few days just to see if it has any effect and if not  then I will raise the call.

As always, thank you for your help.

Kind regards,

Simon