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Author Topic: G.fast Modem Options  (Read 674 times)

Alex Atkin UK

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Re: G.fast Modem Options
« Reply #15 on: September 16, 2020, 09:58:40 PM »

The only thing I can think is seeing the line rate does give you a guideline for setting QoS on your router.  Other than that, I'm personally looking forward to never needing to see the stats again.
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Exchange: INTAKE (ECI) ISP/Modems: Zen (Home Hub 5A running OpenWrt) + Plusnet (VMG-3925-B10B) + Three (Hauwei B535-232)
Router: pfSense (i5-7200U) WiFi: Ubiquiti nanoHD

Robbie

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Re: G.fast Modem Options
« Reply #16 on: September 18, 2020, 11:27:15 AM »

Sounds like routing is all sorted and a modem wouldn't provide the ability to set static routes over CLI anyway as it's a modem - link layer only.

If you're bereft of line stats and tweaking via G.fast you're really not going to like FTTP  :lol:

As you know, the more popular aftermarket 'modems' are really routers in disguise; depending on firmware they usually have their CLI exposed too.

For VDSL I used a Vigor 130 and with it only having a single LAN port the accessing of its web GUI, CLI or line stats offered a small hurdle to overcome.  Using the modem's CLI a set a route along the lines of:
Code: [Select]
ip route add 10.0.1.0 255.255.255.0 10.0.0.1 static back to my router to allow easy access to the modem from the LAN side of the router.  It could be done via NAT masquerade too, but a simple route via CLI is arguably more elegant.  I didn't run the standard BT SIN firmware on the modem either as the alternate loads played better with my ECI cab.

It looks like my optimism for using improved or tweaked firmware for G.fast may have been misplaced.  As to the agony of having FTTP, well that would be a pain I could live with(!) but alas I don't think it will trouble my area for a number of years.

Still very early days for my G.fast experience & hoping the line 'training' and interleaved profile will end soon.
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re0

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Re: G.fast Modem Options
« Reply #17 on: September 18, 2020, 11:56:40 AM »

What were your estimates and what is your current speed? How far away are you from the cabinet?

G.fast starts off as fast as possible. If it has gotten worse since provision, then perhaps your line can't cope with 3 dB SNRM - the DLM can set it anywhere from 3 to 28 dB, in 1 dB steps (downstream and upstream independently of each other).

By the way, to my knowledge, G.fast doesn't use the interleaving. It uses Impulse Noise Protection (INP). There is nothing to really change.
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Robbie

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Re: G.fast Modem Options
« Reply #18 on: September 18, 2020, 04:05:58 PM »

What were your estimates and what is your current speed? How far away are you from the cabinet?

@re0

100M to cabinet, 140M by wire (hard to say where that extra 40m is given the simple street layout).  All copper, all ducted, no line issues with VDSL with a sync of 89 / 28 Mbps.

G.fast Estimated: 287 / 44.9 Mbps (241.3 / 31.6 Mbps degraded).

Test equipment on installation:

Line: All greens

Maximum Data Rate: 223.016 / 31.932 Mbps
Actual Data Rate: 159.924 / 30.037 Mbps (ie my 160/30 starting package)
SNR: 10.90 / 3.90 dB
Attenuation: 36.1 / 0.0dB
Capacity: 71.7 / 94.1%
Output Power: 0.00 / 4.10 dBm
Interleave Mode
Interleave Depth: 5 / 4
Bitswap: N/A / N/A
Trellis: On / On
G.INP: Active / Active

Post installation modem sync shown as 144.8 / 28.6 Mbps (via ISP).

BT Availability Checker shows a G.fast Max Observed of 246.25 / 33.31 Mbps (dated 2 days after install)

Current speed test circa 141 / 29 Mbps; latency 15ms (was 8ms on VDSL).

Now at install +10 days, last full modem sync was 8 days ago.
« Last Edit: September 18, 2020, 06:42:18 PM by Robbie »
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re0

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Re: G.fast Modem Options
« Reply #19 on: September 18, 2020, 09:35:35 PM »

I have huge doubts your line is 140m with an attenuation of 36.1 dB. It's probably closer to 250m given those estimates and speeds. I think mine is around 180-190m and my attenuation is somewhere between 29-30 dB.

Which ISP were you on and which are you on now? The differences in latency could be due to different routing used. I am on Zen and the latency can vary up to around 6ms in the worst case - historically, I have had to drop the PPPoE session and connect over and over until I've got the latency/routing I wanted (using ping -t on the host of choice). Have you tried a tracert? Do you have a tracert from your previous ISP/connection that you can compare?

Looks like you should be syncing at the maximum rate for the package, with decent overhead for the downstream (you have spare margin). I know the line data for Zen shows the sync. rate for my line to be about 18 Mbps below the actual sync. rate.
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Robbie

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Re: G.fast Modem Options
« Reply #20 on: September 18, 2020, 11:00:06 PM »

Between my demarcation point and the cabinet via the ducting route is 131m, when measured on Google maps.  The Openreach laptop had the line length at 140m.  The cabinet can be seen from my front windows as it is almost directly in front of us.

I don't think I have a ping plot from vdsl now, but I will check tomorrow.  The BT availability checker did have a higher estimate for our property, but that was reduced by a good chunk in the weeks leading up to the switch.

There are 9 houses on my road, all served by the same cab.  I'm the first with g.fast so nobody to compare with.  Very few g.fast installations in my area. and the guy doing the instal said he was the only local guy who had done the course.  Indeed, I was his first modem-only install.

Previous ISP was BT, current is iDNET.

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bkehoe

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Re: G.fast Modem Options
« Reply #21 on: Today at 09:47:44 AM »

I have huge doubts your line is 140m with an attenuation of 36.1 dB. It's probably closer to 250m given those estimates and speeds. I think mine is around 180-190m and my attenuation is somewhere between 29-30 dB.

Which ISP were you on and which are you on now? The differences in latency could be due to different routing used. I am on Zen and the latency can vary up to around 6ms in the worst case - historically, I have had to drop the PPPoE session and connect over and over until I've got the latency/routing I wanted (using ping -t on the host of choice). Have you tried a tracert? Do you have a tracert from your previous ISP/connection that you can compare?

Looks like you should be syncing at the maximum rate for the package, with decent overhead for the downstream (you have spare margin). I know the line data for Zen shows the sync. rate for my line to be about 18 Mbps below the actual sync. rate.

I agree, my attenuation is 27dB and I'm about 150m from the PCP with how the cable is routed (and have an attainable of around 400/73 most of the time). If you are sure of the distance that the cable takes then somethings up with your line!

As others have said there isn't interleaving on g.fast so latency should be almost equivalent to FTTP. I get approx 8ms from Manchester area to London on BT.
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