Just a follow up...
From my testing so far, I've found:
- MaxDownstreamRate, MaxUpstreamRate and/or setting the SNRM target offset for downstream all work.
Hi again Ixel,
Just for the sake of clarity, what do you mean by "
and/or setting the SNRM target offset for downstream all work." Is that a yes, no or just a maybe?!
It's just that some people might buy a FrizBox, based on what you are reporting here and on ThinkBroadband.
The FritzBox is, however, an expensive (overpriced??) modem, so it could be a costly mistake if that function was found not to work after all (because control of the SNRM is locked by BT's DSLAMs, as many are finding).
What people have discovered with the HG612, as with the FritzBox, is that it is easy to change the SNR target margin for ADSL1/2/2+ and for VDSL2.
However, with a VDSL2 connection, the British Telecom DSLAM (both the ECI and the Huawei) appears to ignore those end-users changes. Instead the DSLAM maintains its own margin, which it adjusts dynamically according to line performance.
Those owning an HG612 (and other Broadcom-based devices) can soon confirm this with the
xdslcmd tool.
Below we see the SNR training (aka target) margin set to default (-1). This shows that the margin is by default decided by the DSLAM:
# xdslcmd profile --show
...
Capability
:..
Training Margin(Q4 in dB): -1(DEFAULT)
Now we can try to tweak the SNRM. In this case halving whatever the default is (usually 6dB):
# xdslcmd configure --snr 50
xdslCtl_GetVersion success
And that end-user change to the margin is confirmed as below:
# xdslcmd profile --show
..
Training Margin(Q4 in dB): 50
Others will confirm that for VDSL2, the request is simply ignored by the DSLAM. Instead, the DLM algorithm running on the DSLAM controller will continue to apply its own (dynamic) SNRM.
My SNR recently, before specifying an upstream sync rate limit, was 6dB~ at the full 20000. It's now 9dB~ at 14992, with downstream around 12dB at 50000.
Will you clarify again what you are saying, please. Earlier, you showed us that the average SNR on your line was fluctuating any way. Isn't that what it is continuing to do now?
Since the line has to re-train to use a new user-specified SNR margin, we should expect to find that tweaking the margin in the CPE causes an immediate and demonstrable change in average SNR. As well as an immediate change in the ATTNDR. Which might be illustrated best through screenshots. Yet it seems you are not reporting that?
P.S. For those interested in trialling the
Ikanos Fusiv Vx180, the chipset found in the FritzBox 7390, there is also the
Sagemcom Fast 2764 which uses an identical DSL platform. The two devices should perform the same on the DSL side.
A vendor in Brazil is selling the
Sagemcom 2764 for R$85 (about £25). A lot cheaper than the FritzBox 7390 at ~£200. [1]
More photos at [2]
cheers, a
[1]
http://produto.mercadolivre.com.br/MLB-432428081-modem-vdsl-wi-fi-power-box-modelo-2764-sagemcom-1-a-100mbps-_JM[2]
http://www.tripleoxygen.net/wp/2012/08/sagemcom-modem-fst-2764-gv-power-box-gvt-teardown/