topic Re: Long timeouts for stale PPPoE connections in Broadband

Long timeouts for stale PPPoE connections

jimbof — Fri, 10 May 2013 09:37:20 GMT

(reposting as it seems my other topic has been missed by plusnet staffers)
Could someone from Plusnet please look into why the timeout for stale PPPoE connections on FTTC is so long (over 6 minutes), when it looks like according to BT SIN495 it should really be configured to time out much quicker.
http://community.plus.net/forum/index.php/topic,114576.msg986509.html#msg986509
I have the technology to fix this for myself on my own router on OpenWRT with a program that hunts out the stale connections and kills them at your end, but anyone using an off-the-shelf router using rp-pppoe and pppd (many routers, including the ASUS models from looking at the logs posted in some other threads) will experience 6+ minutes before they can reconnect their connection in the event of router being powercycled or possibly DLM kicking in.
Having your PPP timeouts so high will lead to customers with lines which DLM kicks in on being quite unhappy as everytime it happens they will lose their connection for 6 minutes or more. I can see several posts on here which look like this kind of thing going on.
If it is deliberately configured to time out so slowly it would be nice to understand why.

Re: Long timeouts for stale PPPoE connections

Anotherone — Fri, 10 May 2013 09:44:06 GMT

A number of people have reported it as being about 8 minutes. However if you drop your own PPP session by clicking Disconnect, you can reconnect again immediately.
Edit: I don't know if Kelly may be one of the best to respond to this.

Re: Long timeouts for stale PPPoE connections

jimbof — Fri, 10 May 2013 09:52:04 GMT

Yes, but there are many situations where you don't have the option to drop the connection nicely. It does seem that this behaviour goes against Openreach's advice for implementation of FTTC, and will inevitably lead to support questions. As a service provider I'd try and do anything I could to reduce support issues and improve customer satisfaction, so either this is a misconfiguration (and should probably be fixed) or it is trying to achieve some goal (such as preventing denial of service attacks on authentication servers).
Would like to see some comment from Plusnet staff on why it is configured like this.

Re: Long timeouts for stale PPPoE connections

njay — Fri, 10 May 2013 12:38:36 GMT

Not all routers allow you to drop the PPP connection via the router Webpage.
My TP-Link 8960n didnt although admittedly that was an ADSL modem/router which had been reconfigured to use a LAN port as a WAN. The only way to drop it was to hit the reboot option in the menu which I hope did actually disconnect 1st before rebooting. I suspect it may have as the PPP connection re established way quicker than 6/8mins.

Re: Long timeouts for stale PPPoE connections

Anotherone — Fri, 10 May 2013 12:56:51 GMT

Yes some ADSL modem/routers are a bit of a pain in that respect as it doesn't allow a graceful disconnect. A power off for 10 minutes is generally the next best option.
I would certainly expect that something that was configured as just a router where the broadband username and password were entered on it, when rebooted would drop the PPP session and automatically reconnect as the reboot completed.
On Fibre this isn't the same as the connection being dropped modem side, where this 8 minutes seems to come into play.
I've been led to believe that Dave from Plusnet is looking into this "feature".

Re: Long timeouts for stale PPPoE connections

jimbof — Fri, 10 May 2013 13:12:22 GMT

Quote from: Anotherone
Yes some ADSL modem/routers are a bit of a pain in that respect as it doesn't allow a graceful disconnect. A power off for 10 minutes is generally the next best option.
I would certainly expect that something that was configured as just a router where the broadband username and password were entered on it, when rebooted would drop the PPP session and automatically reconnect as the reboot completed.

OpenWRT (up to Attitude Adjustment at least) doesn't cleanly close PPPoE sessions on reboot either, though disconnect on their webUI does work.
The biggest issue is that having lost the session (however that may have happened, be it server side or at the customers premisess) most customers don't have any way to kill the session as their router no longer has the details in it required to close the session after a reboot! (specifically the session ID) which can only be recovered by sniffing the WAN interface.
As I have a solution for my own purposes which is robust now I don't very much care, but I can see how life would be much easier for many customers, if this timeout value were reduced. I'm going to have to patch up my router every time I firmware upgrade, which is a bit of a pain. And I could have done with getting some sleep the last few nights instead of hacking ethernet frames in my pyjamas!

Re: Long timeouts for stale PPPoE connections

njay — Fri, 10 May 2013 13:23:09 GMT

Quote from: Anotherone
Yes some ADSL modem/routers are a bit of a pain in that respect as it doesn't allow a graceful disconnect. A power off for 10 minutes is generally the next best option.
I would certainly expect that something that was configured as just a router where the broadband username and password were entered on it, when rebooted would drop the PPP session and automatically reconnect as the reboot completed.
On Fibre this isn't the same as the connection being dropped modem side, where this 8 minutes seems to come into play.
I've been led to believe that Dave from Plusnet is looking into this "feature".

Not quite sure what distinction you are making?
I used the 8960n on my Fibre connection and although I didn't have the opporitunity to do the preferred disconnect from 8960n's webpage which I could do with the 582n (similar arrangement what were originally ADSL mode/routers being firmware modified for use on Fibre) I didn't experience any difference in reconnection times with the 8960n reconnecting automatically once it had rebooted, a process that took under 2mins from initiating reboot in menu to being back up and browsing t'internet
Interestingly I have An Asus n66u and I haven't disconnected or rebooted that yet so who knows if that will exhibit any symptoms? Something that was seen by another member when they rebooted their Asus router and sufferred 5-7min timeout on WAN reconnect?

Re: Long timeouts for stale PPPoE connections

jimbof — Mon, 13 May 2013 09:20:21 GMT

I've registered a support ticket for this as I've not seen any input from Plusnet staff. I realise this forum isn't the official channel for support so hopefully I'll get some info via the ticket system.

Re: Long timeouts for stale PPPoE connections

adamwalker — Tue, 14 May 2013 08:24:23 GMT

Hi there,
I'm sorry we've not replied to you yet. This is something we're already aware of and are looking into at the moment.
I understand you've raised a ticket but the CSC agents probably won't be aware of this issue. I'll make sure one of us gets back to you when there's some development.
Adam

Re: Long timeouts for stale PPPoE connections

jimbof — Tue, 14 May 2013 09:04:32 GMT

Thanks for the reply Adam. FYI the ticket number is 69514911, and indeed the CSC agent wasn't aware of the issue.
It's good that you are looking into it as I'm sure it will help out many in future if you can solve it. In my case it caused me a right headache when trying to get a different router up and running, and I know you say in the guides that you should wait 15 minutes etc after plugging in the router, but the reality is that is an "eternity" when you are trying to get something up and running, and really no-one can believe there is any sane reason why a router would need to be on a fibre connection for 15 minutes to "set up" when my ADSL would sort itself out in seconds.
For my own purposes I have a solution as mentioned which hunts out the stale session on the WAN interface and builds a PADT for it so you tear down the session. If anyone wants the source for the modified version of pppoesk which I have made then give me a shout. I can't give much support for it though, just know it works for me!

Re: Long timeouts for stale PPPoE connections

Anotherone — Tue, 14 May 2013 10:35:10 GMT

I'd be interested if you could PM with some details jimbof. By the way don't get confused with the 15 minutes that it suggests you wait for allowing the TR-069 ACS to configure your username and password - you can short cut that and do it manually, you can also turn off the function. This is different from the issue of this PPPoE timeout.

Re: Long timeouts for stale PPPoE connections

jimbof — Tue, 14 May 2013 11:04:45 GMT

OK I wasn't aware of the autoconfig setup; but the comment still stands that anything taking that long on a fibre line seems suboptimal at best, and probably broken if you're feeling ungenerous!

Re: Long timeouts for stale PPPoE connections

bobpullen — Tue, 14 May 2013 12:22:01 GMT

Further to what Adam's posted, we've an internal problem open to track progress for this one (ref: 75285). As far as I know the PPP timeout's set to eight minutes which I think stems from back in the dial-up days. The current situation isn't ideal as it's likely to cause certain customers confusion, something that's been proved by the multiple threads that have cropped up here. It could also drive support contacts from the less technically minded.
Thanks for bringing it to our attention and thanks for the investigative work. It's appreciated
More news as we have it ...

Re: Long timeouts for stale PPPoE connections

jimbof — Tue, 14 May 2013 12:39:36 GMT

Thanks Bob, appreciate the reply. Seems that the recommendation from BT (from SIN495 details provided by user njay) is less than 20secs, which is going to be less than most routers take to boot up so probably makes all these issues disappear.

Re: Long timeouts for stale PPPoE connections

Anotherone — Tue, 14 May 2013 12:55:20 GMT

Thanks for your reply Bob. As some have been reporting modem reboots about as quick as 10 seconds or so, and SIN498v4p3 states retrain times can be between 10-60 seconds (para.2.1.6) wouldn't an 8 second timeout be more appropriate - what issues if any would that cause?
@njay

Quote from: njay
I used the 8960n on my Fibre connection and although I didn't have the opporitunity to do the preferred disconnect from 8960n's webpage which I could do with the 582n (similar arrangement what were originally ADSL mode/routers being firmware modified for use on Fibre) I didn't experience any difference in reconnection times with the 8960n reconnecting automatically once it had rebooted, a process that took under 2mins from initiating reboot in menu to being back up and browsing t'internet
Interestingly I have An Asus n66u and I haven't disconnected or rebooted that yet so who knows if that will exhibit any symptoms? Something that was seen by another member when they rebooted their Asus router and sufferred 5-7min timeout on WAN reconnect?

Ah, I hadn't seen that, sorry, so the Asus doesn't seem to do a graceful disconnect then if that's the way it's behaving.
Edit: correction due to misreading of quote as they say, should have gone to specsavers

Re: Long timeouts for stale PPPoE connections

bobpullen — Tue, 14 May 2013 13:17:33 GMT

Quote from: Anotherone
Thanks for your reply Bob. As some have been reporting modem reboots about as quick as 10 seconds or so, and SIN498v4p3 states retrain times can be between 10-60 seconds (para.2.1.6) wouldn't an 8 second timeout be more appropriate - what issues if any would that cause?

That's something we need a bit of time to look into.

Re: Long timeouts for stale PPPoE connections

njay — Tue, 14 May 2013 13:25:45 GMT

Always surreal when you come onto a post and see you've been quoted from elsewhere lol
What I was saying in that quote was more about the 8960n in that it had no means to do a graceful disconnect. However by opting to reboot the 8960n from its menu it rebooted very quickly and reestablished suggesting it was doing a graceful disconnect prior to the reboot?
I haven't as yet on the Asus I am now using had to reboot it soon idea if it will exhibit timeout. And I certainly don't want to try as that will No doubt jinx my current high and stable line speed lol.

Re: Long timeouts for stale PPPoE connections

Anotherone — Tue, 14 May 2013 13:33:52 GMT

Sorry, I misread what you'd said, I'll go back and edit that post. (The distinction I was trying to make originally was that rebooting a modem/router on ADSL doesn't give a graceful disconnect - never mind - we will be going off topic).

Re: Long timeouts for stale PPPoE connections

w23 — Tue, 14 May 2013 13:43:25 GMT

There's a bit more info in BT SIN 498:

Quote
2.1.6 Downstream shaping
The CP is expected to shape the downstream traffic to match the actual VDSL2 line rate in order to avoid excessive traffic loss.
CPs should be aware that the mechanism for reporting the downstream and upstream line rates relies on a line re-train causing the CP, or the CPE, to initiate a new PPP session or a new DHCP request. The success of this method of line rate reporting is down to the CP's choice of timers used around PPP/DHCP handling.
If the PPP/DHCP survives a re-train, then the CP will be unaware of any change in the line rate and will not be able to shape appropriately.
The line re-train time for VDSL2 can be anywhere between 10 and 60 seconds, with typical values in the 20-30 second range.

I appreciate this will not likely be an overnight fix, the above specifically explains why correct timing is important in keeping the Plusnet line speed setting correct to avoid dropped packets and other issues.

Re: Long timeouts for stale PPPoE connections

Anotherone — Tue, 14 May 2013 14:13:57 GMT

It's not likely to be an overnight fix and I think that is why Bob has said they will need some time to look into it for example to make sure an 8 second timeout that I suggested might be more appropriate and doesn't cause other issues. Mind you, I only said 8 seconds because it's currently 8 minutes, I suppose 9.9 seconds would do!