Perhaps the BRAS hasn't been updated by the router?

Who knows? Original thoughts last time was a profile error somewhere in a back office system that was being propagated through, or not being updated correctly ...

Everything suggests 20Mbps is easily achievable, results from Speedtests show it has been that way for 18 months ... and why should a single reboot cause the problem?

Do you have a HH5 you can use instead of the modem and router?

In reply to a post by BatBoy:

Do you have a HH5 you can use instead of the modem and router?

No, but it would not work anyway. I use the VOIP interface on the 2701 to provide two voice circuits.

The Business version was tried previously and the problem remained. Changing between Huawei and ECI modems does not resolve it - although ECI gives 2 Mbps faster download.

As I understand it, the router is responsible for updating the BRAS

How or why? What information do they hold that the Modem does not? The User name and password, maybe, but little else. The BT speedtester acknowledges that I should have a 20Mbps upload so that is correct.

As it happens I have tried it using a couple of 2701s, and Business Hubs with no difference.

The BRAS is responsible for limiting the thoughput to ensure you don't flood the modem and cause it to drop packets. The BRAS needs to have the correct IP profile information. Perhaps ask BT to reset the BRAS?

SIN 498 says:

1.2.1 VDSL2 rates
The upstream and downstream VDSL2 data rate is reported to the CP BRAS/Radius upon PPP discovery (a similar mechanism exists for DHCP � see Section 2.1.7 ).

and:

2.1.6 Downstream shaping
The CP is expected to shape the downstream traffic to match the actual VDSL2 line rate in order to avoid excessive traffic loss. CPs should be aware that the mechanism for reporting the downstream and upstream line rates relies on a line re-train causing the CP, or the CPE, to initiate a new PPP session or a new DHCP request. The success of this method of line rate reporting is down to the CP's choice of timers used around PPP/DHCP handling. If the PPP/DHCP survives a re-train, then the CP will be unaware of any change in the line rate and will not be able to shape appropriately. The line re-train time for VDSL2 can be anywhere between 10 and 60 seconds, with typical values in the 20-30 second range.
As DHCP typically uses lease timeouts in the order of days rather than seconds, CPs intending to use DHCP are advised to consider the impact of downstream line rate changes on their service and any strategies they could adopt if they wish to shape downstream traffic in close relationship to the active line rate.

So you may be able to force the BRAS to re-evaluate the profile by terminating the PPP session for a minute or two then restarting.

You could do this by using the 'disconnect' function within the router then reconnect after a minute or so, or even unplug the router from the modem for a while then reconnect it to re-establish PPP.

[Edit to include more relevant info]

Edited by deleted (Sun 07-Sep-14 12:41:36)

Been though that loop many times - either directly or indirectly. Changed router, changed modem, routers reset to default and rebuilt ... The BT Techs - who spent three full afternoons on site could not resolve even when working with second line support and the product team (effectively third and fourth line).

It refers to a line re-train, so a modem disconnect, wait, power cycle and reconnect should be enough.

The mechanism is driven by PPP discovery, so disconnecting and reconnecting the PPP session should be enough. You should ask BT what the BRAS profile is set to.