Kitz Forum

Broadband Related => Broadband Hardware => Topic started by: Robbie on September 11, 2020, 11:48:54 AM

Title: G.fast Modem Options
Post by: Robbie on September 11, 2020, 11:48:54 AM
I have been a happy user of a Vigor 130 for the VDSL years so the switch to a locked-down MT992 has left me bereft when it comes to line stats, line tweaking and the ability to set a route via CLI.

So what are my options:

- Purchase an unlocked MT992 - Expensive and erratic availability?
- Purchase a Vigor 166 v1 - New but potentially hobbled?
- Wait for the Vigor 166 v2 - Vapourware?
- Something else?

The second option looks the cheapest and quickest but the protracted delay, presumably due to issues with the product, may suggest teething issues with the router/modem.  I'm not sure the reduced frequency range of the V1 will be a practical concern given the roll-off but it still may cause incompatibility issues at a later date.

Anyone with experience of a more tweakable G.fast modem than the Openreach MT992?

Regards to all.
Title: Re: G.fast Modem Options
Post by: Alex Atkin UK on September 11, 2020, 12:31:32 PM
I don't recall seeing any discussion about line tweaking for G.fast to be honest, its not something common enough for it to come up much.

Line stats would certainly be interesting, but are they a priority?
Title: Re: G.fast Modem Options
Post by: hushcoden on September 11, 2020, 01:36:51 PM
What about a ZyXEL XMG3927-B50A ?
Title: Re: G.fast Modem Options
Post by: re0 on September 11, 2020, 01:43:18 PM
I use the Zyxel XMG3927-B50A, which has access to stats via UI and CLI (so it works with DSLstats). Broadcom chipset, very stable, decent features, very good wireless. I know it's not just a modem but rather a modem-router combo, but it may be worth considering. Though, expect to pay upwards of £150 for it brand new, that's even if you can find it in stock. AAISP may still stock them, so you could contact them.

Looks like there is a single listing on eBay (https://www.ebay.co.uk/itm/NEW-Zyxel-Ieee-802-11Ac-Ethernet-Modem-Wireless-Router-2-40-Ghz-Ism-Band-5-Ghz-/392911794115) for one, opened but unused if you're willing to give it a punt for a smidge under £100 buy it now - says it's XMG3927-B50A-EU01V1F, but I don't know which plug type it will include (but the PSU has exchangeable plugs, at least with my model, so you could always contact Zyxel I suppose).

As for tweaking, I have never tried. G.fast targets 3 dB by default anyway. Even if tweaking is possible, it would probably be a bad idea.
Title: Re: G.fast Modem Options
Post by: Robbie on September 11, 2020, 02:28:35 PM
Thanks - can the Zyxel be operated in bridged / modem only mode (ie to keep the routing on my router)?


Title: Re: G.fast Modem Options
Post by: re0 on September 11, 2020, 02:36:53 PM
It does have a bridge mode, but I've not personally configured or used it.
Title: Re: G.fast Modem Options
Post by: Robbie on September 11, 2020, 02:47:35 PM
Thanks again.  I'll do some digging around to see if supports the usual stuff (pppoe, chap, baby jumbos et al).

I've not been on this forum for years and it is good to see it thriving.

Not sure why my IPv4 address is displaying though.

Edit: Doh!   :blush:
Title: Re: G.fast Modem Options
Post by: re0 on September 11, 2020, 03:23:16 PM
As a routing device, it connects over PPPoE using 1500 MTU. But if I can recall correctly, the interface used for bridging must have an MTU of 1508 to accommodate the 8 byte overhead for the full 1500. Upon inspecting the ifconfig output from the CLI, it looks like it'll only be 1500, thus restricting you to 1492 bytes over a bridge using PPPoE. I remember when I tried to use bridging mode with my old Billion modem-router combo with a MikroTik, I recall having issues and don't think I even managed it with modified firmware from Billion themselves.

Don't take this as conclusive since I haven't tried to use it, but the ifconfig output does not give much hope. I know there is a 2 year old discussion here (https://forum.kitz.co.uk/index.php/topic,21273.0.html) which may be somewhat relevant even though it is referring to older chipsets and models from Zyxel.
Title: Re: G.fast Modem Options
Post by: burakkucat on September 11, 2020, 04:43:41 PM
- Purchase an unlocked MT992 - Expensive and erratic availability?

To date, I am unaware of anyone who has unlocked such a device.

And while I think of it: Welcome to the Kitz forum.  :)

Edited to add: I've only just read your later posts . . .

I've not been on this forum for years and it is good to see it thriving.

You must have previously been using a different forum identity.
Title: Re: G.fast Modem Options
Post by: niemand on September 11, 2020, 05:51:34 PM
Do you know how to read G.fast line stats?

CLI routing change - presume own router can do this, or can be done via GUI as will only need static routes LAN-side.

CHAP support I am not sure what you mean here?
Title: Re: G.fast Modem Options
Post by: Robbie on September 11, 2020, 09:01:49 PM
To date, I am unaware of anyone who has unlocked such a device.

And while I think of it: Welcome to the Kitz forum.  :)

Edited to add: I've only just read your later posts . . .

You must have previously been using a different forum identity.

Hi & thank-you.  Yes, had to grab another ID as I failed to remember anything useful to grab my old one.  Heck, rembering my name is challenge enough.

I'm not aware of an unlock of the Openreach modem either; my thought was more towards buying an unadulterated Huawei version but it's my least favoured option given the availability and price.

Title: Re: G.fast Modem Options
Post by: Robbie on September 12, 2020, 04:51:57 PM
CHAP support I am not sure what you mean here?

CHAP is one of the PPPoE authentication methods used by many UK ISPs.  Some ISPs use an extended CHAP format, some add a full two-way ID and password auth process whilst others (eg BT) use a dummy or nominal ID & password which is effectively ignored. 

I've come across modems/routers that may not provide the extended CHAP format or work correctly with a real & authenticated pre-shared password.  Others manage the full CHAP routine but don't permit an MTU above 1492 on handshake, effectively becoming the bottleneck for baby jumbo frames, even if the routers at either end supports them.
Title: Re: G.fast Modem Options
Post by: niemand on September 13, 2020, 12:56:00 AM
I am aware what CHAP is I just have no idea what you're referring to having never encountered authentication issues across any ISP or bit of kit. I'm not aware of any that require anything other than the basics which anything claiming to support PPP should support.

Please do point me to one for my own information. :)

Seems an appropriate router with baby jumbo support, no modem required, would hit the spot. Mikrotik kit might well hit the spot and is worth looking at. Don't need anything too awesome for UK twisted pair speeds

G.fast lines work somewhat differently from VDSL, not least the ability of it to perform rate adaption in less than a millisecond and this to be the response to errors.
Title: Re: G.fast Modem Options
Post by: Robbie on September 13, 2020, 02:44:14 PM
Please do point me to one for my own information. :)

Seems an appropriate router with baby jumbo support, no modem required, would hit the spot.

I'll have a dig around for a truncated or reduced MRU CHAP auth for you.  Don't seem to have one to hand but I think archived a BT ISP pppoe log with a reduced MRU via CHAP on an older Draytek.  Usually under something like
Code: [Select]
show interfaces pppoe pppoe0 log | cat for those playing along.

Pretty happy with my routers.  I tend to use an EdgeRouter-4 as my main, with an ER-8 for test configurations, although I do keep an ER-3 as a racked / warm spare.  They do all I need really.
Title: Re: G.fast Modem Options
Post by: niemand on September 16, 2020, 01:02:10 PM
Fair enough.

That's a new one to me. CHAP frames are tiny. I cannot imagine a PPPoE link where they have to be fragmented or truncated. Even ATM links would be taken care of by AAL5 sitting underneath PPP in the protocol stack.

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. The MT992 seems good. Given G.fast runs on 3dB SNR margin and the protocol itself is optimised I'm not sure what would be tweaked, especially if already at the maximum throughput cap Openreach set.

If you're bereft of line stats and tweaking via G.fast you're really not going to like FTTP  :lol:
Title: Re: G.fast Modem Options
Post by: Alex Atkin UK 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.
Title: Re: G.fast Modem Options
Post by: Robbie 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.
Title: Re: G.fast Modem Options
Post by: re0 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.
Title: Re: G.fast Modem Options
Post by: Robbie 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.
Title: Re: G.fast Modem Options
Post by: re0 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.
Title: Re: G.fast Modem Options
Post by: Robbie 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.

Title: Re: G.fast Modem Options
Post by: bkehoe on September 19, 2020, 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.
Title: Re: G.fast Modem Options
Post by: Robbie on September 19, 2020, 01:38:57 PM
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.

Thanks guys.  When the Openreach guy showed me the routing of the ducts on his laptop nothing jumped out at me as unusual with the routing but the graphic was not rich with detail - the rough routing is annotated below.  The ducting path depicted is around 131m, direct to cab is just under 120m.  The cabinet itself is under the trees at the top / northern point of the picture:

(https://www.disco3.co.uk/gallery/albums/userpics/10700/normal_Ducts.jpg)

So as I understand it the attenuation is too high for my apparent line length and given that my speed is well-below expected levels the logic is totally sound.  I’d be surprised to find another 110m in the ducting length somewhere though, even with a healthy error margin - it’s just a cul-de-sac with 9 houses.  I’m home later so shall have a wander around to look for the BT manhole covers.

I re-synced the modem this morning (install +11 days) with 8.5 days since last restart.  No change in reported sync rate from my ISP.

Ping plot from this morning:

(https://www.disco3.co.uk/gallery/albums/userpics/10700/normal_Ping_Plot_Trace.jpg)

G.fast Max Observed:

(https://www.disco3.co.uk/gallery/albums/userpics/10700/normal_Screenshot_2020-09-19_at_13_27_42.jpg)

Install Line Test:

(https://www.disco3.co.uk/gallery/albums/userpics/10700/normal_IMG_1536.jpeg)

Install G.fast Tests:

(https://www.disco3.co.uk/gallery/albums/userpics/10700/normal_IMG_1538.jpeg)

(https://www.disco3.co.uk/gallery/albums/userpics/10700/normal_20200908-G_fast_Engineer_Test_Equipment_223_0_31_9_Mbps_Max_Attainable.jpeg)
Title: Re: G.fast Modem Options
Post by: re0 on September 19, 2020, 02:37:40 PM
Well, attenuation cannot be accurately translated into distance, and vice-versa - at least not practically. Though it can be pretty accurate if you know the path, grade of copper/aluminium, etc.

I'd suspect that it's possible that the extra approx. 100m in [electrical] length is due to aluminium and/or thin copper, along with the route not being so direct.

I suppose when the engineer came for install, they renewed your master socket? Are you using the master socket and not a slave socket?

I can't really see your trace, but perhaps you could do some testing and see if dropping and reconnecting PPPoE gives you better/worse latency/routing. And try it a few times.

By the way, I made a mistake. Interleaving is applied, but delay is not - at least not by default, and I didn't see anything in the SIN about interleave delay being used.
Title: Re: G.fast Modem Options
Post by: Robbie on September 19, 2020, 03:29:20 PM
It's all copper, thankfully, and around 13 years old.

Yep, new master socket with the modem directly on the IDC pair, with around 60cm of cat5e to the modem sitting on the floor under a set of drawers - all in an effort to make it wife-friendly.
Title: Re: G.fast Modem Options
Post by: Robbie on September 19, 2020, 03:40:28 PM
The back of the socket is the external wall with the BT wiring entry point from the ducting, so very little extra wiring:

(https://www.disco3.co.uk/gallery/albums/userpics/10700/normal_IMG_1559.jpeg)
Title: Re: G.fast Modem Options
Post by: bkehoe on September 19, 2020, 06:19:29 PM
Just a thought but sounds like your ISP is showing you the IP Profile of your line rather than the sync rate itself. Your speed test results seem perfectly normal for a 160MBit sync, albeit if you were wanting a faster package at some stage then of course the attenuation is an issue.

The fastest speed tests I get on my 330MBit sync is around 291MBit and thats only by picking a server that has the capacity for example.
Title: Re: G.fast Modem Options
Post by: re0 on September 19, 2020, 06:50:41 PM
Absolutely what I was thinking. Speeds are normal for the sync. According to the checker (max observed speeds), the most he could expect anyway would be about 246/33 Mbps if he upgraded.

The mystery of the distance may remain a mystery, but it's safe to say there is nothing that can be done about it unless you wanted to pay for an alternative solution (FTTP, leased line, etc.).

As for the latency, the difference in 8ms vs 15ms is very small on a larger scale. What I can say with confidence is that G.fast is not adding a delay to it - in theory, it can be slightly quicker than VDSL2. The delay is certainly coming from beyond the DSLAM, which is down to how your connection to the internet is routed with your ISP.
Title: Re: G.fast Modem Options
Post by: Robbie on September 19, 2020, 07:13:32 PM
All of the unexpected / additional latency is on hop 2, so noteworthy I think.

ISP provided info: Sync Speed - 144.8 Mbps Down / 28.6 Mbps Up
- Gives me circa 140.9 Mbps on the usual speed testers, so seems about right from a headline 144.8 Mbps sync speed.

(https://www.disco3.co.uk/gallery/albums/userpics/10700/normal_Sync_Speed_2.jpg)

I've dropped a note to my ISP.  The package plan was to start on the 160/30 plan and then migrate upwards as you can move up but not down in the first year - an ISP recommendation at order time in order to see the actual line conditions.

After years of VDSL this is all learning for me.
Title: Re: G.fast Modem Options
Post by: bkehoe on September 19, 2020, 08:25:41 PM
Robbie, I'm 99% sure they're quoting you the IP profile rather than sync speed.

I've just checked the BTW speed test and on my 330 sync the IP profile is 303.13 and as I've mentioned before tests max out not much more than 290mbit which all makes sense so what you're seeing on your 160 package implies a full 160 sync.
Title: Re: G.fast Modem Options
Post by: Robbie on September 19, 2020, 08:38:14 PM
Thank-you.

20 Mbps is quite an overhead!
Title: Re: G.fast Modem Options
Post by: re0 on September 19, 2020, 10:14:58 PM
I sync at 330 Mbps and get about 293 Mbps throughput in the best case. So, ignoring IP profiles, I get about 0.89% of the sync rate.

If you're getting about 141 Mbps, then using 0.89% would sorta match up.

It's certainly a large overhead, I would agree.
Title: Re: G.fast Modem Options
Post by: adslmax on May 27, 2021, 03:12:56 AM
I sync at 330 Mbps and get about 293 Mbps throughput in the best case. So, ignoring IP profiles, I get about 0.89% of the sync rate.

If you're getting about 141 Mbps, then using 0.89% would sorta match up.

It's certainly a large overhead, I would agree.

My G.fast are much similiar to Robbie 160/30 as Openreach test kit say max data rate are 210/29 compare to him 223/31 and my real throughput speed is 151/27.8 with TalkTalk Business (this test run direct to ethernet 2.5Gbps) from TP Link WAN port 1Gbp connected to Openreach Gfast Modem 1Gbp lan port via samknows speed test.

My gfast line attenuation are 38.0dB SNR at 4.0dB (downstream) no interleaved

Title: Re: G.fast Modem Options
Post by: dslexpert on June 07, 2021, 02:14:39 PM
- Wait for the Vigor 166 v2 - Vapourware?

Old thread, but the Vigor 166 definitely exists and I think it's the only one that's ever shipped in the UK; the v2 supports 212Mhz which Openreach say they will never support in the UK as it interferes with other services (crosstalk etc.)
Title: Re: G.fast Modem Options
Post by: j0hn on June 07, 2021, 02:32:14 PM
Old thread, but the Vigor 166 definitely exists and I think it's the only one that's ever shipped in the UK.

There's a dedicated thread on these forums to reviewing the vigor 166.
So far everyone with the vigor 166 has a v1 and not a v2.

Seeing as OpenReach don't use frequencies above 106MHz it makes little difference to own a v1 or v2 in the UK.
Title: Re: G.fast Modem Options
Post by: smallal on June 07, 2021, 10:04:06 PM
There's a dedicated thread on these forums to reviewing the vigor 166.
So far everyone with the vigor 166 has a v1 and not a v2.

Seeing as OpenReach don't use frequencies above 106MHz it makes little difference to own a v1 or v2 in the UK.
I've been playing with a GEN2 model from Germany & can report that here in the UK it's performance is just the same as the GEN1.
In fact they even share the same firmware (as of v4.1.1 - currently running V4.2.3)
Incidentally, for anyone with an EU GEN1 or GEN2 model, DrayTek in Germany now has a dedicated BETA firmware page here:
http://draytek.com/download_de/Firmwares-Modem/Vigor160-Serie/Vigor166/BETA-TEST/