Puzzling Speed Degradation

[#1]

@Townman  As the OP is running DSLStats as seen in the attachment in message #4 I would assume that the modem/router is not a Hub1 as DSLStats requires a Broadcom modem chip. What we have not determined in this thread is why the sync speed dropped so low and stayed there, however things are looking a lot better now. Maybe some line monitoring is required in future.

[#2]

What we have not determined in this thread is why the sync speed dropped so low and stayed there

Are we sure it stayed there ? After the first drop, the sync speed MAY have come back but the PlusNet profile could well still have been set at the lower value. Only after the second restart would any increased PN profile take effect and given the OP is on a static IP it would have been limiting throughput.

[#3]

@MisterW 

@RealAleMadrid 

@Townman 

Guys I appreciate your perspectives and have noted what you say. For example I was not aware that opting for a static IP limited throughput, I will look into that.

As for being kinder, I'm not knocking the tech support people I spoke to, they were invariably courteous and tried to help but they limited thermselves e.g .one person simply refused to believe that my router was flagging up a 16dB down SNRM, which was clearly a major clue. 

And I will be monitoring for a while to ensure things have settled down.

[#4]

@BobR 

For example I was not aware that opting for a static IP limited throughput, I will look into that.

It doesn't per-se. To explain a little more, Plusnet maintain a line profile ( Current Line Speed ) alongside the BT profile. This PN profile SHOULD follow any change in the BT profile ( which will follow changes in sync speed ) but a) can sometimes get 'stuck' and b) requires that the PPPoE session is dropped for any change to take effect. This profile used to limit downstream throughput within the PN systems independently of the BT profile. It now is largely not used and has no effect EXCEPT for connections that use static IP's, since these are routed differently over the PN network.

So the bottom line is that, if everything is operating correctly, then a static IP will perform (throughput wise) exactly the same as a dynamic one. However if the PN profile is lower than it should be, then it will limit thoughput.

Hope that helps explain

[#5]

@MisterW

Thanks for that explanation - very helpful.

[#6]

Bob,

To put it another way, it is one of the non-standard considerations which might not be in the usual issue profiling for it is something related to legacy workings and not something expected to influence matters.  Frankly it is detail which I would not expect all agents to be aware of.

EDIT: Here is a current example of said problem - https://community.plus.net/t5/Fibre-Broadband/Speed-dropped-off-a-cliff-overnight/m-p/1811944#M12382...