In general, though not infallibly, it pays to have the ECI modem for an ECI FTTC cabinet and an HG612 v3B on a Huawei one.
If on an ECI cabinet I doubt if it matters much. If on a Huawei then they support G.INP as does the HG612. That is a huge advantage if your line has interleaving on. ECI kit so far as I know still doesn't support it.
Interleaving on FTTC adds at least 8ms to latency and costs several Mbps downstream sync. At highish speeds, as much as 10Mbps can be lost.
G.INP is a more recent error correction method Openreach have introduced that reduces interleaving to a very low level and normally restores the lost sync and removes the extra 8ms latency. It works by resending corrupt packets rather than messing around in low-powered user kit trying to correct errors in-flight through sophisticated software.
Kindness isn't going to cure the world of all its awfulness but it's a good place to begin. Daisy Ridley.
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