How common are PPP disconnections with VDSL2?

I'd like to hear from people who are getting VDSL2 through BT's FTTC offering (whether with BT or some other ISP). How common are PPP disconnections for you? The output of pppd on my Linux box (being used as my router, directly connected to the Openreach VDSL modem) shows that I am getting somewhat regular, though intermittent disconnections.

Sometimes the connection will stay up for 2 weeks, some days it will disconnect and reconnect 4 or 5 times. I have been told by Zen customer support that generally this is considered "stable" for VDSL2 because it is an unreliable technology and there's no 100% uptime guarantee. Whilst I understand this, it does seem like a very high level of unreliability considering I had literally months on end with no downtime back when I had ADSL2+ from Be, supposedly one of the less reliable ISPs. These disconnections aren't "invisible" either; for the 30 or so seconds that the disconnection/reconnection occurs, I lose the internet connection; no ping responses, IRC and other protocols requiring a constant connection drop out, etc.

Obviously I'm supposing this is a problem between my modem and the exchange, and not with my ISP, but it still seems bad; my line sounds fine on a quiet line test so why the regular disconnections? I've tried plugging the modem into a filter connected directly to the test socket too, to eliminate the internal wiring as a problem; the disconnections still occurred. I'd appreciate it if people could reply with their experiences; uptime/performance graphs would be good too.

In reply to a post by jez9999:

Whilst I understand this, it does seem like a very high level of unreliability considering I had literally months on end with no downtime back when I had ADSL2+ from Be, supposedly one of the less reliable ISPs.

I don't have any stats for you,but note that BE doesn't use PPP. It sounds as if you're now on a PPP connection so you're using any of the ISPs that operate over the WBC platform. If you were with Sky FTTC for example you'd have a similar setup to BE. (but currently no static IP).

Its possible the PPP connections is dropping and restarting, to force a new IP (if you're on dynamic), or because some RAS server somewhere fell over.

In terms of reliability, the guys at AAISP track this stuff to a heavy degree.

In reply to a post by jchamier:

I don't have any stats for you,but note that BE doesn't use PPP. It sounds as if you're now on a PPP connection so you're using any of the ISPs that operate over the WBC platform.

As per Jez's sig, he's now on Zen FTTC. What I don't know is whether he's on the Zen backhaul network or BT Wholesale WBMC - "View line data" in the customer portal will show which.

My Zen WBMC based FTTC connection can manage PPP connections lasting for several months.

In reply to a post by David_W:

My Zen WBMC based FTTC connection can manage PPP connections lasting for several months.

I missed the sig. My BT connection is hard to tell as I was so used to BE and having a TBB BQM set up that with the dynamic IP the BQM doesn't work, and I miss it.

Having just looked through my RT-N66U log, I don't seem to have had a PPP restart down since power cycling the router on the 7th Nov.

I don't have any persistent storage attached, so its just an in memory log.

Currently got a PPP outage since 3pm today coincidence.

area fault tho which BT seemed a bit too quick to declare fixed. As the status page says for my area fault started 2.54pm fixed about 20 mins later, wrong its still ongoing now, 8 router reboots and 1 hour 40 mins later after ringing BT tech support fault finally raised.

Normally tho with this fault aside it depends.

Earlier in the year BT seemed to be terminating my PPP session at least once a week, maybe for forced ip rotation as the sync was stable. When I disabled cwmp access those PPP terminations stopped and I have had long PPP uptimes since. Prior to today I had the PPP session since I stopped testing the hh5 which I think was about 6 weeks.

In reply to a post by David_W:

In reply to a post by jchamier:

I don't have any stats for you,but note that BE doesn't use PPP. It sounds as if you're now on a PPP connection so you're using any of the ISPs that operate over the WBC platform.

As per Jez's sig, he's now on Zen FTTC. What I don't know is whether he's on the Zen backhaul network or BT Wholesale WBMC - "View line data" in the customer portal will show which.

How do you determine which it is, on that page?

In reply to a post by jez9999:

In reply to a post by David_W:

What I don't know is whether he's on the Zen backhaul network or BT Wholesale WBMC - "View line data" in the customer portal will show which.

How do you determine which it is, on that page?

Above the chart, it will say "Your current line technology is WBMC" if you're on BT Wholesale - or something else if you're on the Zen network.

Whilst you're in that screen, does it show repeated changes in the synchronisation speed of your line?

In reply to a post by David_W:

In reply to a post by jez9999:

In reply to a post by David_W:

What I don't know is whether he's on the Zen backhaul network or BT Wholesale WBMC - "View line data" in the customer portal will show which.

How do you determine which it is, on that page?

Above the chart, it will say "Your current line technology is WBMC" if you're on BT Wholesale - or something else if you're on the Zen network.

Whilst you're in that screen, does it show repeated changes in the synchronisation speed of your line?

Looks like I'm on BT Wholesale.

And no, I don't see repeated changes.

came back online during the night.

For the 18 months I was with BT on Infinity2 I had maybe about 3 reconnects, usually in the early hours of the morning, so probably to do with work being carried out, and one outage which lasted about 3 hours, no problems so far on PN

I don't monitor my PPPoE connections, but I've never noticed a case where it was broken except by VDSL reconnection or my explicit intervention. Usually even VDSL reconnection has not broken the PPPoE connection, and I have had to go in manually to make sure my IP profile is correctly updated. That said, I see now a VDSL up time of 559 hours (23 days), but PPPoE of only 9 days; I may get several short PPPoE connection drops I never even notice.

VDSL connection has typically stays up for months at a time, except where there are significant line issues. The change 23 days ago was caused by DLM improving my profile and removing interleaving, and there was another about a week before when the modem firmware was updated ... probably the reason that DLM was later able to improve profile.

"except by VDSL reconnection"? Surely that would mean a break in your internet connection, like if you were connected to IRC it would drop out?

if the ip stays the same things like irc connecitons can survive, luck of the draw if falls between keepalive packets.

If the ip changes, then yes its a cert disconnection on irc etc.

Edited by Chrysalis (Thu 21-Nov-13 13:23:06)

In reply to a post by jez9999:

Looks like I'm on BT Wholesale.

And no, I don't see repeated changes.

If you were seeing repeated changes in line speed, that would indicate frequent VDSL2 resynchronisation, which would certainly cause problems.

It's probably worth talking to Zen to find out if there's anything in their logs indicating why PPP is dropping out. I know you've said previously when you asked for suggestions for LCP Echo Request/Reply parameters that it's as if data transfer stops sometimes, then the PPP session is torn down due to a lack of LCP Echo Replies. This suggests possible interference with the VDSL2 signal, but there could easily be another cause..


Unfortunately, without the use of a hacked modem (which would give you some local statistics) or some information from Zen, it's going to be hard to figure out what is happening.


As a point of reference. my current PPPoE session has been up since October 26, when my router rebooted after a lengthy power cut that exhausted my UPS batteries.

Already talked to Zen; they say that from their POV the PPP connection is stable. They also say that things are considered stable until you get up to about 5 dropouts a day because "VDSL is an imperfect technology".

In reply to a post by jez9999:

"except by VDSL reconnection"? Surely that would mean a break in your internet connection, like if you were connected to IRC it would drop out?

That's what I would have expected. BUT, if the VDSL connection and reconnection is quick enough, the higher level connection does not notice. It may be that if the higher level connection was more active at the time it would notice quicker? The usual VDSL reconnection is for DLM changes and happens in the middle of the night when I am asleep.

Some people see the same as me, and almost always need to do a manual PPPoE reconnection to reestablish correct IP profile. Others almost always lose PPPoE even for a quick VDSL reconnection. I'm not sure what makes for the different situations. (I'm on HG612 and HH3b)

In reply to a post by StephenTodd:

Others almost always lose PPPoE even for a quick VDSL reconnection. I'm not sure what makes for the different situations. (I'm on HG612 and HH3b)

I guess the PPPoE driver in the HH3b is quite relaxed about missing a few status packets, and so there is time for a VDSL resync. I've not seen the same on my line (HG612 with Asus RT-N66U, the HH3b is in its box in the loft). I've seen useful improvement in speed and latency since the firmware upgrade mid Oct to the HG612, but I had to manually reboot my router (easier to hit power switch on back than to login to web and restart PPP) to get the profile to update.

I've not seen the same on my line but I had to manually reboot my router to get the profile to update.

To me, that implies that you (like me) didn't lose PPPoE connection on VDSL resync, or else the IP profile would have updated.

Maybe there is a missing part of the system I don't understand, and the IP profile reset is not based on PPPoE connection, or ...?

In reply to a post by jez9999:

Already talked to Zen; they say that from their POV the PPP connection is stable. They also say that things are considered stable until you get up to about 5 dropouts a day because "VDSL is an imperfect technology".

I would say that as many as 5 drops in PPPOE or PPPOA sessions within say 7days isn't within normal limits, I wouldn't want or expect 5 within any month, So many drops would have a significant impact on any connection, IMO

Edited by tommy45 (Thu 21-Nov-13 22:04:56)

In reply to a post by StephenTodd:

I've not seen the same on my line but I had to manually reboot my router to get the profile to update.

To me, that implies that you (like me) didn't lose PPPoE connection on VDSL resync, or else the IP profile would have updated.

Yes, that makes sense, and I'd read that VDSL supported SRA - and its probable this is occuring but the IP profile doesn't update. Could be a good reason to move to Sky who don't use an IP profile

Maybe there is a missing part of the system I don't understand, and the IP profile reset is not based on PPPoE connection, or ...?

Others have reported improving speeds by just reconnecting PPP, forces the WBC IP Profile to update based on the Openreach DSLAM sync speed?

In reply to a post by tommy45:

In reply to a post by jez9999:

Already talked to Zen; they say that from their POV the PPP connection is stable. They also say that things are considered stable until you get up to about 5 dropouts a day because "VDSL is an imperfect technology".

I would say that as many as 5 drops in PPPOE or PPPOA sessions within say 7days isn't within normal limits, I wouldn't want or expect 5 within any month, So many drops would have a significant impact on any connection, IMO

agree shocking standards, but I guess when reading zen's t&c's one may understand why, its clear zen are not an isp to fight openreach on faults and so this sort of policy then isnt too surpising. I believe tho the defenition of broadband isnt just speed it also has to be "always on", 4 drops a day to me falls foul of that but thats just my opinion.

The Openreach implementation of VDSL2 does not currently include SRA. SIN 498 does point out to the SP that their PPP timeout needs to take care of the fact that a re-sync can take as little as 20 seconds. Many SPs seem to ignore that and therefore fail to drop and re-establish PPP.

Edit - SIN number had the "9" missing .

Edited by RobertoS (Sat 23-Nov-13 00:51:10)

SRA is incompatible with how BTw operates, the fact they trying to make it a requirement to have low ppp timeouts.

From a end user standpoint its preferable for PPP to stay connected, it preserves the ip and reduces the impact of an outage, but from BT's standpoint it breaks their ip profile system which they insist on keeping.

Interesting as well is some peep's on 330mbit FTTP reporting lower ip profiles O_o down to just over 200mbit.

In reply to a post by RobertoS:

The Openreach implementation of VDSL2 does not currently include SRA. SIN 48 does point out to the SP that their PPP timeout needs to take care of the fact that a re-sync can take as little as 20 seconds. Many SPs seem to ignore that and therefore fail to drop and re-establish PPP.

Shame no SRA - and its interesting that Openreach's biggest SP doesn't get this right either, assuming the PPP timeout is set at the RAS end.

In reply to a post by Chrysalis:

SRA is incompatible with how BTw operates, the fact they trying to make it a requirement to have low ppp timeouts.

SIN 498 specification for non-Openreach modems:-

"R.VDSL2.9 The modem shall support seamless rate adaptation (SRA) as defined in Section 13.1 of G.993.2 [3]."

So it seems Openreach are looking into it.

Edited by RobertoS (Sat 23-Nov-13 00:57:27)

In reply to a post by jez9999:

I'd like to hear from people who are getting VDSL2 through BT's FTTC offering (whether with BT or some other ISP). How common are PPP disconnections for you? The output of pppd on my Linux box (being used as my router, directly connected to the Openreach VDSL modem) shows that I am getting somewhat regular, though intermittent disconnections.

I've not noticed any issues and I check my TBBQM fairly frequently. With a static IP address I wouldn't notice a short disconnect unless one happened while I was using the network. I've not heard of anyone else seeing frequent reconnects so I suspect the fault lies with your equipment.

Edited by Andrue (Sat 23-Nov-13 11:42:33)

In reply to a post by RobertoS:

In reply to a post by Chrysalis:

SRA is incompatible with how BTw operates, the fact they trying to make it a requirement to have low ppp timeouts.

SIN 498 specification for non-Openreach modems:-

"R.VDSL2.9 The modem shall support seamless rate adaptation (SRA) as defined in Section 13.1 of G.993.2 [3]."

So it seems Openreach are looking into it.

and sra is defaulted to enabled on the new hg612 firmware.

But it still remains incompatible with existing IP profile mechanisms.

In reply to a post by Chrysalis:

Interesting as well is some peep's on 330mbit FTTP reporting lower ip profiles O_o down to just over 200mbit.

Are they paying for 330Mb or are they on 160Mb Infinity 3?

All those I saw on the BT forum are on 160Mb Infinity 3. The speed that the IP Profile is set at would approximately match the expected speed from the new 220Mb/20Mb Openreach product.

These guys were likely provisioned on 330Mb/20Mb as that was all that was available and will be moved to 220Mb/20Mb when the Openreach contract is up.

In reply to a post by Chrysalis:

and sra is defaulted to enabled on the new hg612 firmware.

Where does that come from?

In reply to a post by Chrysalis:

and sra is defaulted to enabled on the new hg612 firmware.

But it still remains incompatible with existing IP profile mechanisms.

It doesn't need to be compatible. SRA's job is to keep a line active by rate adapting downwards in event of lower than tolerable SNR hence the modem won't go above the IP profile'd level.

As you may remember from UKOnline with SRA the only way is down.

In reply to a post by RobertoS:

SIN 498 specification for non-Openreach modems:-

"R.VDSL2.9 The modem shall support seamless rate adaptation (SRA) as defined in Section 13.1 of G.993.2 [3]."

So it seems Openreach are looking into it.

The current firmware for the Huawei HG612 (remotely updated in October 2013) has SRA configured "on". This is a new development, as the previous firmware version had it set "off".

Edit: I see Chrysalis has already mentioned this. To answer your follow-on question Bob, that configuration parameter can be seen when the firmware image is examined and contrasted with the previous version of the image.

Edited by burakkucat (Sat 23-Nov-13 16:08:38)

Thanks. I just couldn't see it from what we usually telnet. I've now found:-

# xdslcmd profile --show

Modulations:
        G.Dmt   Enabled
        G.lite  Enabled
        T1.413  Enabled
        ADSL2   Enabled
        AnnexL  Enabled
        ADSL2+  Enabled
        AnnexM  Disabled
        VDSL2   Enabled
Phone line pair:
        Inner pair
Capability:
        bitswap         On
        sra             On
        trellis         On
        sesdrop         Off
        CoMinMgn        Off
        24k             On
        phyReXmt(Us/Ds) Off/On
        TpsTc           AvPvAa
        monitorTone:    On
        dynamicD:       On
        dynamicF:       Off
        SOS:            On
        Training Margin(Q4 in dB):      -1(DEFAULT)
#

Edit - there is of course a command to (try to) turn it off. I don't feel like trying it, as I expect it to work and that would almost certainly cause a re-sync that I don't want.

Not sure whether the command will be:-

xdslcmd configure --sra off
or
xdslcmd configure1 --sra off
or either, or
xdsl configure/configure1 --sra off

Edited by RobertoS (Sat 23-Nov-13 17:50:42)

Yes, that's it.

If you would like, I could install the original Asbokid unlocked firmware image onto a testing HG612, harvest all the information, then install the Howling Wolf unlocked firmware image and repeat the information harvest. An sdiff (sideways difference) will then clearly show all the changes in configuration that Beattie has implemented.

Please let me know and I will put it on my "ToDo" list.

trying to remember, did I ever sync during a period of interference and then when the snrm came back SRA pumped my speed up? hmm. no idea I have archived much data and still do have my cacti graphs intact but I dont recall ever syncing up with SRA during noise bursts because SRA was so good the line never dropped meaning I never had to. So my only experience was starting out at a optimal sync, sync would go down during bursts, recover again later but I dont recall it ever going above the starting sync. So yeah I guess.

Worth pointing out tho although on kitz forums its been shown SRA is enabled on the modem I dont think its actually active and working yet.

Not my field LOL. xdslcmd will do for me.