Reommended VDSL2 router for new FTTC connection

[Chris Green]

We have just got FTTC available. I'd like to squeeze the best
bandwidth we can out of it so what not too ridiculously priced VDSL2
routers are recommended?

We currently have two phone lines both with ADSL, one has a venerable
Draytek Vigor 2820n for ADSL and the other has a BT Home Hub3, the
Draytek does load balancing of the two ADSL connections.

I believe the Home Hub3 can connect VDSL2 so it might provide an
initial connection at least until I decide on new hardware (if
necessary). It says the current firmware is Version
4.7.5.1.83.8.94.1.49 (Type A).

We will probably move to using a single FTTC connection instead of the
load balanced 2 x ADSL so a relatively expensive router like a Draytek
isn't necessary from that point of view. So I'm probably looking for
a 'simple' router with the best possible VDSL2 performance.

Any/all recommendations very welcome.

--
Chris Green
·

[Graham J]

Who are the two ISPs you use for connectivity at present? Do you intend
to use one of these for the upgrade to FTTC?

Whatever, the supplier of FTTC will probably offer you a "free" router
for the cost of postage. This at least will probably report the actual
sync speed and noise margin of the FTTC service - essential if you wish
to optmise performance.

Other than that, congestion is probably the next most important factor
so choose an ISP with a good reputation for its backhaul.

How important is reliability to you?

Do you use the Draytek 2820n for its features such as VPN, traffic
graphing, syslog reporting, bandwith control of its clients, and the
like? If so, I would recommend you keep it and add a simple FTTC modem
- for example the Vigor V130. However this solution will deny you the
performance monitoring of the FTTC service.

--
Graham J

[Chris Green]

Graham J <gra...@invalid.com> wrote:
> Chris Green wrote:
> > We have just got FTTC available. I'd like to squeeze the best
> > bandwidth we can out of it so what not too ridiculously priced VDSL2
> > routers are recommended?
> >
> > We currently have two phone lines both with ADSL, one has a venerable
> > Draytek Vigor 2820n for ADSL and the other has a BT Home Hub3, the
> > Draytek does load balancing of the two ADSL connections.
> >
> > I believe the Home Hub3 can connect VDSL2 so it might provide an
> > initial connection at least until I decide on new hardware (if
> > necessary). It says the current firmware is Version
> > 4.7.5.1.83.8.94.1.49 (Type A).
> >
> > We will probably move to using a single FTTC connection instead of the
> > load balanced 2 x ADSL so a relatively expensive router like a Draytek
> > isn't necessary from that point of view. So I'm probably looking for
> > a 'simple' router with the best possible VDSL2 performance.
> >
> > Any/all recommendations very welcome.
> >
>
>
> Who are the two ISPs you use for connectivity at present? Do you intend
> to use one of these for the upgrade to FTTC?
>

PlusNet and PlusNet. :-) I did consider two different ISPs but
decided that it wouldn't really offer much better reliability - in
reality the most likely reason for an outage here is a tree falling on
the wires.

> Whatever, the supplier of FTTC will probably offer you a "free" router
> for the cost of postage. This at least will probably report the actual
> sync speed and noise margin of the FTTC service - essential if you wish
> to optmise performance.
>

Yes, what do PlusNet provide? Is it the Thompson Tecnicolour?

> Other than that, congestion is probably the next most important factor
> so choose an ISP with a good reputation for its backhaul.
>

Hmm, out in the sticks where we are I'm not sure how serious an issue
that is.

> How important is reliability to you?
>

Fairly but not to the level of spending lots more money, we used to
run a small business here (hence two lines) but don't any more. As
noted above the most likely failure here is simply wires down due to
wind etc. I suspect, more money won't help that.

> Do you use the Draytek 2820n for its features such as VPN, traffic
> graphing, syslog reporting, bandwith control of its clients, and the
> like?

Just the load balancing really, might use VPN one day but not at the
moment.

> If so, I would recommend you keep it and add a simple FTTC modem
> - for example the Vigor V130. However this solution will deny you the
> performance monitoring of the FTTC service.
>

Yes, that's one possibility.

--
Chris Green
·

[Nick Leverton]

In article <l215rd-...@esprimo.zbmc.eu>, Chris Green <c...@isbd.net> wrote:
>We have just got FTTC available. I'd like to squeeze the best
>bandwidth we can out of it so what not too ridiculously priced VDSL2
>routers are recommended?
>
>We currently have two phone lines both with ADSL, one has a venerable
>Draytek Vigor 2820n for ADSL and the other has a BT Home Hub3, the
>Draytek does load balancing of the two ADSL connections.
>
>I believe the Home Hub3 can connect VDSL2

I don't think it does natively, we had one here until recently. It can
do PPPo* to connect through an external VDSL modem though.

Nick
--
"The Internet, a sort of ersatz counterfeit of real life"
-- Janet Street-Porter, BBC2, 19th March 1996

[Woody]

In this context does VDSL2 mean there will be a modem on the end of
the line that needs a router to handle the signalling connected by
Ethernet, or are you looking for a modem router that will accept
incoming VDSL2 direct from a landline.

ISTR the BT HH5 does the latter, as does the new BT 'Smart' router.


--
Woody

harrogate3 at ntlworld dot com

[7]

Your FTTC connection cost about £50 a month to Bhtee if they
ordered a symmetric gigabit fibre from
Hyperoptic B4RN Gigaclear or Cityfibre etc.

If they split it a 50 ways, you could be paying 1 pound for
your 20 mbit service so you may get away with a £1 router
to save money.

[Chris Green]

Nick Leverton <ni...@leverton.org> wrote:
> In article <l215rd-...@esprimo.zbmc.eu>, Chris Green <c...@isbd.net> wrote:
> >We have just got FTTC available. I'd like to squeeze the best
> >bandwidth we can out of it so what not too ridiculously priced VDSL2
> >routers are recommended?
> >
> >We currently have two phone lines both with ADSL, one has a venerable
> >Draytek Vigor 2820n for ADSL and the other has a BT Home Hub3, the
> >Draytek does load balancing of the two ADSL connections.
> >
> >I believe the Home Hub3 can connect VDSL2
>
> I don't think it does natively, we had one here until recently. It can
> do PPPo* to connect through an external VDSL modem though.
>

Ah, thanks, maybe that's it. I've let PlusNet send me a 'free'
modem/router so should be OK to start with.
--
Chris Green
·

[Chris Green]

Woody <harro...@ntlworld.com> wrote:
> In this context does VDSL2 mean there will be a modem on the end of
> the line that needs a router to handle the signalling connected by
> Ethernet, or are you looking for a modem router that will accept
> incoming VDSL2 direct from a landline.
>
> ISTR the BT HH5 does the latter, as does the new BT 'Smart' router.
>

I think I need to have this explained :-)

There will be a POTS line coming in the window which needs to connect
to something. Currently with ADSL it connects to my Draytek Vigor
2820n router.


--
Chris Green
·

[Nick Leverton]

The Plusnet Hub One (to which we just upgraded too) is essentially a
badged BT Home Hub 5a, I gather. Does OK for 'free' anyway :) And is
supported by LEDE and OpenWRT if extra features are needed.

[Woody]

"Chris Green" <c...@isbd.net> wrote in message
news:7ce5rd-...@esprimo.zbmc.eu...

ADSL and VDSL are just data streaming formats. You can either have a
modem router that will do the whole job - like the HH5a - or you can
have a simple modem that interfaces to the line and gives an ethernet
connection to a special router that does the VDSL decoding.

If you are getting a HH5a then it is just a simple line plug-in like
your ADSL was.

[Chris Green]

Thank you for that scintllatingly useful comment.

--
Chris Green
·

[Chris Green]

Nick Leverton <ni...@leverton.org> wrote:
> In article <otb5rd-...@esprimo.zbmc.eu>, Chris Green <c...@isbd.net> wrote:
> >Nick Leverton <ni...@leverton.org> wrote:
> >> In article <l215rd-...@esprimo.zbmc.eu>, Chris Green <c...@isbd.net> wrote:
> >> >We have just got FTTC available. I'd like to squeeze the best
> >> >bandwidth we can out of it so what not too ridiculously priced VDSL2
> >> >routers are recommended?
> >> >
> >> >We currently have two phone lines both with ADSL, one has a venerable
> >> >Draytek Vigor 2820n for ADSL and the other has a BT Home Hub3, the
> >> >Draytek does load balancing of the two ADSL connections.
> >> >
> >> >I believe the Home Hub3 can connect VDSL2
> >>
> >> I don't think it does natively, we had one here until recently. It can
> >> do PPPo* to connect through an external VDSL modem though.
> >>
> >Ah, thanks, maybe that's it. I've let PlusNet send me a 'free'
> >modem/router so should be OK to start with.
>
> The Plusnet Hub One (to which we just upgraded too) is essentially a
> badged BT Home Hub 5a, I gather. Does OK for 'free' anyway :) And is
> supported by LEDE and OpenWRT if extra features are needed.
>

Ah, thank you, that's useful to know. I have openwrt running on a
Microtik router here so that is a possibility. Does openwrt on the
PlusNet device support the VDSL2 connection?

--
Chris Green
·

[Andy Burns]

Nick Leverton wrote:

> The Plusnet Hub One [...] is essentially a badged BT Home Hub 5a
> And is supported by [...] OpenWRT

That's quite a surprise

<https://wiki.openwrt.org/toh/bt/homehub_v5a>

[Nick Leverton]

Haven't tried it myself but Yes according to the pages which Andy Burns
linked to. The contributor even gives the FTTC settings for Plusnet.

[Graham J]

Chris Green wrote:

[snip]

>> Who are the two ISPs you use for connectivity at present? Do you intend
>> to use one of these for the upgrade to FTTC?
>>
> PlusNet and PlusNet. :-) I did consider two different ISPs but
> decided that it wouldn't really offer much better reliability - in
> reality the most likely reason for an outage here is a tree falling on
> the wires.

According to ISPs by far the most common cause of an internet connection
failure is incompetence of the user or faulty hardware at the user's
premises.

But for this ng I discount that (perhaps unwisely), so in reality the
most common cause of failure is the Openreach cable infrastructure -
trees falling on the wires (as you suggest), bad joints, aluminium
cable, technician working on lines for another customer, etc.

But failures in the backhaul can happen, and using two different ISPs
can minimise that inconvenience.

[snip]

>> Other than that, congestion is probably the next most important factor
>> so choose an ISP with a good reputation for its backhaul.
>>
> Hmm, out in the sticks where we are I'm not sure how serious an issue
> that is.

Probably much more serious than in a large town. The "pipe" between
your local exchange and the rest of the internet may be quite small, and
all it would take would be one or two heavy users to saturate it.

Very likely the "pipe" is actually carried by microwave link, and is
susceptible to interruptions by lightning. I also live in a small
village, and I use two ISPs in a load balancing arrangement. A very
common failure when there are thunderstorms about is that both lines
will lose their PPPoE connections but both show good ADSL sync.

>
>> How important is reliability to you?
>>
> Fairly but not to the level of spending lots more money, we used to
> run a small business here (hence two lines) but don't any more. As
> noted above the most likely failure here is simply wires down due to
> wind etc. I suspect, more money won't help that.

A sensible alternative might be a 3G dongle plugged into your V2820n
router - so for a relatively trivial cost you would have a backup
connection. A&A offer this solution with automatic failover and the
same static IP address. Of course being in the sticks you probably
don't get any sort of mobile phone signal! Another difficulty is that
the 3G dongle needs to be as high as possible, and that isn't easy with
a USB device.

As an aside - does anybody produce a 3G modem with a PoE connection all
in a weatherproof housing which could be mounted at the top of a tall
pole? Then it would be nice if the WAN2 connection on the Vigor router
provided PoE.

--
Graham J

[Chris Green]

Graham J <gra...@invalid.com> wrote:
> >> Other than that, congestion is probably the next most important factor
> >> so choose an ISP with a good reputation for its backhaul.
> >>
> > Hmm, out in the sticks where we are I'm not sure how serious an issue
> > that is.
>
> Probably much more serious than in a large town. The "pipe" between
> your local exchange and the rest of the internet may be quite small, and
> all it would take would be one or two heavy users to saturate it.
>
> Very likely the "pipe" is actually carried by microwave link, and is
> susceptible to interruptions by lightning. I also live in a small
> village, and I use two ISPs in a load balancing arrangement. A very
> common failure when there are thunderstorms about is that both lines
> will lose their PPPoE connections but both show good ADSL sync.
>

I have to say that our connection is incredibly reliable, I don't
think it has failed at all for several years. I've had the occasional
DNS failure but that sort of thing has mostly been fixable with
configuration changes (i.e. I was using a very old DNS server that
eventually went away).

> >
> >> How important is reliability to you?
> >>
> > Fairly but not to the level of spending lots more money, we used to
> > run a small business here (hence two lines) but don't any more. As
> > noted above the most likely failure here is simply wires down due to
> > wind etc. I suspect, more money won't help that.
>
> A sensible alternative might be a 3G dongle plugged into your V2820n
> router - so for a relatively trivial cost you would have a backup
> connection. A&A offer this solution with automatic failover and the
> same static IP address. Of course being in the sticks you probably
> don't get any sort of mobile phone signal! Another difficulty is that
> the 3G dongle needs to be as high as possible, and that isn't easy with
> a USB device.
>

We have poor 3G here though something with an external aerial can
work. I have to balance my mobile on the window cill to get a
reliable connection.

> As an aside - does anybody produce a 3G modem with a PoE connection all
> in a weatherproof housing which could be mounted at the top of a tall
> pole? Then it would be nice if the WAN2 connection on the Vigor router
> provided PoE.
>

You could use the TP-Link style POE 'injector', a little box with two
RJ-45 sockets and a power connection for a wall wart.

--
Chris Green
·

[Chris Green]

Thank you, that would seem to be the way to go then, at least initially.

--
Chris Green
·

[7]

Murghh... twas nuffin.

My house fibre ready through self service but Bhtee VM Openroach Offconn
won't give me a fibre connection for £50 a month by 2020.

I order these items to install my own fibre to the home:

cleaver -$62- https://www.aliexpress.com/item/9-In-1-Fiber-Optic-FTTH-Tool-Kit-with-FC-6S-Fiber-Cleaver-and-Optical-Power/32647289225.html

Fiber junction box - $7 https://www.aliexpress.com/item/KELUSHI-wholesale-FTTH-FTTH-fiber-panel-fiber-optic-terminal-junction-box-86-information-panels-86-Desktop/32598550478.html

So my house is FTTH ready through self help.

So I have fibre in hand ready, and standing out there gawking at all the
telecom company vans buzzing by and waving them down to give me
a connection but is anyone from Bhtee VM Openroach Offconn
going to give me a symmetric fibre connection for £50 month?

Nope.

They just give me a strange look and run away :(

3% of UK households already cabled up with 1Gbit symmetric fibre - so why doesn't
bhtee vm offconn openroach give me a connection?
They have the same identical connection to their junction boxes where
they muliplex all their copper signals into symmetric 1 gigabit fibre for £50 a month.

So why don't they just take a spare fibre and give me a connection?

[Chris Green]

Chronos <use...@chronos.org.uk> wrote:

> On Sat, 1 Apr 2017 22:07:13 +0100
> Chris Green <c...@isbd.net> wrote:
>
> > Ah, thank you, that's useful to know. I have openwrt running on a
> > Microtik router here so that is a possibility. Does openwrt on the
> > PlusNet device support the VDSL2 connection?
>

> Yes. I have one running LEDE right now. It is exactly the same hardware
> as the HomeHub 5 type A and has a Lantiq chipset which can handle all
> *DSL modulation schemes up to VDSL2 using OpenWRT/LEDE with the
> correct vendor blob loaded. 128MB flash and 128MB memory, dual core MIPS
> processor, 2.4GHz 802.11N 300Mbps and 5GHz 802.11AC 1200Mbps. They
> really are, for a freebie, a rather nice router.

Excellent, thank you, a freebie router that I get with my connection
that also runs a sensible OS - what more could one want? :-)

--
Chris Green
·

[Brian Gregory]

On 01/04/2017 21:25, Woody wrote:
> ADSL and VDSL are just data streaming formats. You can either have a
> modem router that will do the whole job - like the HH5a - or you can
> have a simple modem that interfaces to the line and gives an ethernet
> connection to a special router that does the VDSL decoding.

No.

The connection from the modem to the router will be PPPoE.

The router doesn't need to do anything VDSL related to make PPPoE work.

On your side of the modem your router just does PPPoE, it is irrelivant
that the connection on the far side of the modem is VDSL.

>
> If you are getting a HH5a then it is just a simple line plug-in like
> your ADSL was.

--

Brian Gregory (in the UK).
To email me please remove all the letter vee from my email address.

[Brian Gregory]

On 01/04/2017 17:28, Chris Green wrote:
> I believe the Home Hub3 can connect VDSL2

Only with an extra VDSL2 modem such as the HG612.

The red "VDSL" connector on the HH3 is for a PPPoE connection to a
separate modem, such as a VDSL2 modem.

You may be given one with your new connection.

[Andy Burns]

Brian Gregory wrote:

> The red "VDSL" connector on the HH3 is for a PPPoE connection to a
> separate modem, such as a VDSL2 modem.
> You may be given one with your new connection.

I don't think openreach have given out modems for over a year now.

[Chris Green]

Brian Gregory <bvdvgvrv...@gmail.com> wrote:
> On 01/04/2017 17:28, Chris Green wrote:
> > I believe the Home Hub3 can connect VDSL2
>
> Only with an extra VDSL2 modem such as the HG612.
>
> The red "VDSL" connector on the HH3 is for a PPPoE connection to a
> separate modem, such as a VDSL2 modem.
>
> You may be given one with your new connection.
>

Thank you for the clarification, I hadn't really looked very hard at
what the HH3 has, I just noticed it had 'a connection for FTTC'.

I'm getting a 'free' VDSL2 router included with the connection
upgrade, they have even waived the delivery charge. It's with PlusNet
so I think I get an HH5a.

--
Chris Green
·

[Andy Burns]

I managed to snaffle a HH5a for £7 on eBay, quite straightforward to get
LEDE up and running on it, despite the VDSL chipset not supporting
G.INP, it connects faster then my Billion 8800NL which does

root@hh5a:~# /etc/init.d/dsl_control status

Chipset: Lantiq-VRX200 Unknown
Firmware Version: 5.7.9.9.0.6
API Version: 4.17.18.6
Annex: B
Line Mode: G.993.2 (VDSL2)
Profile: 17a
Data Rate: Down: 79.3Mb/s Up: 19.9Mb/s
Signal Attenuation (SATN): Down: 11.0dB Up: 12.0dB
Noise Margin (SNR): Down: 6.0dB Up: 15.4dB
Max. Attainable Data Rate (ATTNDR): Down: 79.4Mb/s Up: 26.9Mb/s

The 802.11ac wifi is pretty impressive too, using 80MHz channel I've got
three devices that connect at 866Mbps.

Slightly disappointing that it doesn't support baby jumbo frames for
PPPoE, so you get 1492 byte MTU instead of 1500 byte.

[Andy Burns]

Chronos wrote:

> Andy Burns wrote:
>
>> despite the VDSL chipset not supporting G.INP
>

> Not sure that's true. The WD9980 has the same base Lantiq XRX200
> chipset
VRX2x8 for the HH5a according to the openWRT wiki

> and those support G.Inp in the later firmwares. I'm on a Broadcom
> cab, so it's a moot point me trying to test but if you're on a
> Huawei
Yes, I have been using a Billion as a modem which reported G.INP was
enabled.

> I have the binary blob extracted from one of the 9980's
> firmwares that claim to support G.Inp if you'd like to try it?
> (/etc/config/network option firmware stanza)

I did see hints that later firmware supported G.INP, perhaps in one
direction only?

I'll gladly give it a try, see if I can squeeze that last 0.7Mbps out of
the line :-P

[Andy Burns]

Chronos wrote:

> that's the little fly in the ointment. LEDE doesn't report G.Inp as
> enabled, it just shows some obscure hexadecimal capability flags in the
> status report.

OK, I've been poking around in the various dsl* and vdsl* binaries and
wrapper scripts, hoping to find ways to get the bits per tone data etc
out, in a similar way to dsl_stats could from the Billion.

> Anyway, is your e-mail valid? I don't want to put them up publicly as I
> don't have a licence to distribute.

Yes, it's valid
Thanks

[Andy Furniss]

Andy Burns wrote:

> Andy Burns wrote:

> Slightly disappointing that it doesn't support baby jumbo frames for
> PPPoE, so you get 1492 byte MTU instead of 1500 byte.

In what way does it fail?

Do you get an error if you try to set 1508 on the ptm interface?

Just curious, I know nothing about LEDE on a HH5A.

[Andy Burns]

Andy Furniss wrote:

> Andy Burns wrote:
>
>> Slightly disappointing that it doesn't support baby jumbo frames for
>> PPPoE, so you get 1492 byte MTU instead of 1500 byte.
>
> In what way does it fail?

You end-up with pppoe working, but using 1492, no error that I noted,
though I haven't tried very hard (just overrode the MTU to 1508 on the
ptm0.101 VLAN sub-interface, in a similar way that I had done on the
physical eth1 port between my WNDR3800 and Billion in modem mode)

> Do you get an error if you try to set 1508 on the ptm interface?

Not tried on the pmt0 itself, just on ptm0.101

I haven't turned on ppp logging, but I did notice a kernel warning and
stack trace that might be related in the dmesg output

[Andy Furniss]

Andy Burns wrote:
> Andy Furniss wrote:
>
>> Andy Burns wrote:
>>
>>> Slightly disappointing that it doesn't support baby jumbo frames
>>> for PPPoE, so you get 1492 byte MTU instead of 1500 byte.
>>
>> In what way does it fail?
>
> You end-up with pppoe working, but using 1492, no error that I noted,
> though I haven't tried very hard (just overrode the MTU to 1508 on
> the ptm0.101 VLAN sub-interface, in a similar way that I had done on
> the physical eth1 port between my WNDR3800 and Billion in modem
> mode)
>
>> Do you get an error if you try to set 1508 on the ptm interface?
>
> Not tried on the pmt0 itself, just on ptm0.101

A quick test on my desktop eth shows you need to set on the real
interface before the vlan.

> I haven't turned on ppp logging, but I did notice a kernel warning
> and stack trace that might be related in the dmesg output

If you can set 1508, I guess you'll also need to have a search around in
/etc/ppp or gui looking for places to change 1492 to 1500.

Maybe also check iptables for any mss clamping rules.

[Andy Burns]

Andy Burns wrote:

> Andy Furniss wrote:
>

>> Do you get an error if you try to set 1508 on the ptm interface?
>
> Not tried on the pmt0 itself, just on ptm0.101

Just looking at the interfaces with "ip link show"

10: ptm0: <BROADCAST,MULTICAST,UP,LOWER_UP>
mtu 1500
qdisc fq_codel
state UP
mode DEFAULT
group default
qlen 1000
link/ether 34:8a:ae:96:bb:a7 brd ff:ff:ff:ff:ff:ff

11: ptm0.101@ptm0: <BROADCAST,MULTICAST,UP,LOWER_UP>
mtu 1500
qdisc noqueue
state UP
mode DEFAULT
group default
qlen 1000
link/ether 34:8a:ae:96:bb:a7 brd ff:ff:ff:ff:ff:ff

19: pppoe-WAN1: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP>
mtu 1492
qdisc fq_codel
state UNKNOWN
mode DEFAULT
group default
qlen 3
link/ppp

both the ptm and vlan sub-interface show as 1500 mtu, I suppose it might
not make much sense if ppp tries to set the subinterface to a larger mtu
than the base ptm0 interface, I'll try something like

ip link set ptm0 mtu 1508
ip link set ptm0.101 mtu 1508

in some startup scripts, see how far I get next time I'm rebooting it
anyway

[Andy Burns]

Andy Furniss wrote:

> A quick test on my desktop eth shows you need to set on the real
> interface before the vlan.

We both had the same thought!

it was easy to try a quick

ifdown pppoe-WAN1
/sbin/ip link set ptm0 mtu 1508
/sbin/ip link set ptm0.101 mtu 1508
ifup pppoe-WAN1
/sbin/ip link show pppoe-WAN1

21: pppoe-WAN1: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP>
mtu 1500
qdisc fq_codel

state UNKNOWN
mode DEFAULT
group default
qlen 3
link/ppp

And an MTU checker indeed shows I have a working 1500 byte MTU :-)

[Andy Furniss]

Yea, best at boot as long as it's all timed right ....

IIRC if you touch mtu on an interface that pppd is attached to it will
drop the ppp.

I assume LEDE uses roughly the same pppd as me - that won't even try
to negotiate baby jumbos unless the interface mtu is >= 1508.

[Andy Burns]

Andy Furniss wrote:

> I assume LEDE uses roughly the same pppd as me - that won't even try
> to negotiate baby jumbos unless the interface mtu is >= 1508.

The gui (backed by the /etc/config stuff) has an option to set the MTU
of the interface that ppp will sit on top of (ptm0.101 in my case) but I
assume that fails as the underlying ptm0 is still 1500.

I manually set both the ptm0 and ptm0.101 to 1508 and then ppp was happy
to use 1500 rather than 1492, I'll see if I can find a place to increase
just the ptm0 and then hopefully the ppp script will succeed in setting
the pmt0.101 by itself

If that works, I'll consider submitting a LEDE patch that changes the
MTU of the underlying interface before changing the VLAN sub-interface,
if ppp is on a VLAN.

[Andy Furniss]

Nice, depending on how the mtu checker worked, it may be also worth trying

https://www.speedguide.net/analyzer.php

Which looks at what mss tcp is advertising, so you can infer whether
there is still any mss clamping going on.

[Andy Burns]

Andy Furniss wrote:

> depending on how the mtu checker worked, it may be also worth trying
> https://www.speedguide.net/analyzer.php
> Which looks at what mss tcp is advertising

Thanks, not used that one before, it seems happy

TCP options string = 020405b40103030801010402
MTU = 1500
MTU is fully optimized for broadband.
MSS = 1460
Maximum useful data in each packet = 1460, which equals MSS.
Default TCP Receive Window (RWIN) = 65536
RWIN Scaling (RFC1323) = 8 bits (scale factor: 2^8=256)
Unscaled TCP Receive Window = 256

The checker I use sends pings with DF set, and seems to use a binary
chop to home in on the largest size that works.

<http://www.letmecheck.it/mtu-test.php>

[Andy Burns]

Andy Burns wrote:

> I'll try something like
>
> ip link set ptm0 mtu 1508
> ip link set ptm0.101 mtu 1508
>
> in some startup scripts

It didn't even need that. Obviously this method is LEDE/openWRT
specific, using the UCI configuration system, in /etc/config/network I
already had the mtu for the wan interface

config interface 'WAN1'
option proto 'pppoe'
option ifname 'ptm0.101'
option username 'xx...@plusdsl.net'
option password 'xxxx'
option ipv6 'auto'
option delegate '0'
option mtu '1508'

all it took was to add the mtu option to the wan_dev interface

config device 'wan_dev'
option name 'ptm0'
option macaddr 'xx:xx:xx:xx:xx:xx'
option mtu '1508'

rebooted and straight up with working baby jumbos.