when my neighbour had G.INP first enabled on is HH5a he had to wait for the firmware update, then that loaded on and he gained back his normal speed plus another 8-9Mb/s... however this hub later stopped working and a replacement was sent which has old firmware so he saw the loss in speed and rise in latency again for around 5 weeks and then the hub was updated and back to G.INP speeds....
Interesting, but only speculation and anecdotal. The VRX268-based HH5a - with stock firmware - does not provide detailed line characteristics; at least not via its standard web interface. Consequently, with the HH5a, it's impossible to say whether G.INP (ReTX G.998.4) is active on the line, or not.
Notably, those who've replaced the Openreach firmware on their VRX268-based ECI B-FOCuS /r modems - replacing it with OpenWRT plus an updated DSP BLOB said to support G.INP - have yet to confirm that G.INP is now active on their lines. Of course only those on Huawei DSLAMs would be able to test that out any way.
Maybe that sudden boost in speed on your neighbour's line - which he attributed to G.INP being activated on his HH5a - was just the spontaneous remission of a line fault? The fact that the sync speed appeared to rise and fall so dramatically, could simply indicate an intermittent line fault. Nothing to do with G.INP.
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Edited by deleted (Sat 31-Oct-15 15:59:33)