Sync. Speed

My router (Billion 8800NL) reports my downstream sync speed as 79999kbps. It is a stable line (current connection has been up for 45 days, no serious error seconds, about 10 error seconds per hour upstream and no error seconds downstream). Max. attainable various between about 81000 and 86000. The variation is due to some electrical noise from next door which is a holiday let so not permanently occupied. This drops the SNR from about 3.9 to 3.3 or so which hits the max attainable.

When I run the BTW speed test and go into the further diagnostics button, it shows my IP profile and maximum achievable as 74.1 Mbps. TBB speed test averages just short of 69Mbps downstream.

I queried the IP profile with my ISP thinking it should be about 77Mbps. They replied that my sync speed as reported by their radius server logs and the OR FTTC Service Test was 76.325 which makes the 74.1 IP profile a bit more sensible.

What is the reason for the discrepancy in the reported sync speeds?

Probably G.INP (aka Retransmittion) related.
Retransmittion Low has an IP Profile of 96.7% sync speed
Retransmittion High has an IP Profile between 91-92%

You will be on high (most are). It requires a cap on the line to get retx low.

edit:
If you wish to confirm you can telnet in and check your stats.

Bearer 0 - INP-Rein 0 - is Retx Low
Bearer 0 - INP-Rein 1 - is Retx High

Edited by j0hn83 (Tue 27-Nov-18 16:16:26)

In particular with Retransmission High the connection speed reported by the ISPs Radius Server, and used by BT Wholesale to calculate the IP Profile, is lower than the sync speed reported by the user modem.

I have established this by examining my AAISP Radius Server log and comparing what that reports with modem/router's sync speed and my IP Profile.

Thanks both.

G.INP enabled on the downstream but not the upstream. Upstream sync reported both by my router and by the BTW test as 19999 which supports what you say about the Retransmission setting causing a difference.