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[cbdeakin]

Can crosstalk lower the noise margin of lines? Is this the reason why lines may get slower over time, as the DLM reduces  upstream/downstream speed to keep the noise margin at 6db?

Unrelated question - Can SRA cause more line errors to be generated? I noticed after disabling it, packet errors reduced to 0 (so far).

[Chrysalis]

yes, crosstalk essentially is like extra noise on the line, so it erodes the useable SNR.

DLM doesnt directly manipulate speed in response to new or old noise, DLM just intervenes if the line breaches stability thresholds.

Also a SRA setting should have no affect as openreach dont support SRA on FTTC so its always disabled regardless if on or off on the modem.

[cbdeakin]

Thanks for your response Chrysalis.

When I had SRA on, the downstream and upstream rates would change a small amount over time. Now that its turned off, the sync rates don't change..

[ejs]

In theory, SRA is a mandatory requirement specified in BT SIN 498. So you never know, BT might decide to use it one day.

[Chrysalis]

Thanks for your response Chrysalis.

When I had SRA on, the downstream and upstream rates would change a small amount over time. Now that its turned off, the sync rates don't change..

That would indicate it is actually working if the sync speed was varying by small amounts.

This is the first I have heard of SRA working on openreach FTTC tho.