Prior to the stats below when Interleave was switched on, the CRC errors were around 300,000 each day. Since Interleave, CRC / ES now look good but seems high FEC, which I understand are the corrected errors. Is this OK or will DLM try to fix these now?
The general principle of DLM is to reduce CRC errors to FEC ones (or, in the stats, OHFErr into RSCorr), and it employs tools of either setting FEC/Interleaving to various levels (which takes an overhead off the top of your speed), or limiting speeds by employing banding.
Adding FEC and interleaving is the part that creates the RSCorr, while banding would attempt to reduce (or get rid of) both the CRC errors *and* the RSCorr. DLM usually, as a first resort, employs FEC/interleaving. As a second resort, it increases the level, and only as a last resort does seem to employ banding.
It isn't my experience that DLM will attempt to do anything about a high level of RSCorr. It only really seems to care about the CRC count, at least when choosing whether to turn interleaving on (or up).
Your stats don't seem to be suffering enough CRC errors to warrant further intervention right now, but you do have a high level of RSCorr. With ongoing, itty-bitty "correctable" interference, it is easy to see that it may vary somewhat over time, so you should expect that DLM may well alter the amount of interleaving, going up & down.
Right now, these parameters are chosen by DLM for you:
INP: 3.00 0.00
delay: 8.00 0.00
which are fairly standard specifications for interleaving (3 symbols of noise protection, and 8ms maximum delay).
The sync negotiation has taken those 2 parameters, and chosen FEC and interleaving details of:
B: 63 239
R: 16 14
D: 861 1
I: 80 127
N: 80 254
As someone mentioned, the depth (D) is 861, which is an indication of how "spread out" your data is sent, in order for consecutive bytes to not be hit by the same burst of noise.
The FEC protection is running at a 20% overhead (R/N, or 16/80 bytes), which is a mid-level. I've seen higher and lower.
If you see any change in error rates, then DLM will most likely choose new INP and Delay values, and you will see new D, R and N values.
Note also that upstream has employed FEC (R/N is 14/254, or 5%) without interleaving (D=1). That is using a bit of the upstream bandwidth, but not causing any extra latency.
Do you know how long your line is, or how far away the cabinet is?