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PPP dropping regularly? I may have solved it.
26-05-2013, 07:21 PM
Post: #1
PPP dropping regularly? I may have solved it.
I just wanted to feedback with everyone on how my PPP connection has been since I changed the settings on my router.

As hoped, since increasing the number of echo requests that can be lost before dropping the connection, it hasn't dropped at all. That is 27d 19h and counting, which I think is a record for me since joining Origin.

The options I changed are:
LCP echo failure threshold: 6 changed to 10
LCP echo interval: 1 changed to 5
Its worth noting, there is nothing scientific about how I chose the above numbers, I just saw someone mention them when faced with a similar problem on another ISP.

I still suspect this is hiding a deeper problem on the network as I have seen at least one period on my ping graph where traffic appeared to have stopped being passed over the network causing a red spike of packet loss. This is likely where PPP would have dropped before, but as the above settings say do not drop unless the connection is unresponsive for 50 seconds, it hangs on until traffic resumes. It is interesting though as if traffic had really stopped you would expect the Origin PPP server to drop the connection at their end, which obviously didn't happen, so this might not be related at all.

I am going to reduce the values again now as I don't like the idea of having to wait 50 seconds for my connection to come back if I lose sync (although its incredibly rare for that to happen so far). So the interesting question here is, does the connection indeed suddenly stop passing data for more than 6 seconds (the original value), why, and how long for so we can set the values above accordingly.

Now you might think "aren't we just masking the problem?" and yes we are. But having PPP drop then reconnect when the problem occurs takes longer to resume your Internet connection than if the PPP connection stays active, which is why this is a reasonable compromise. There is also the possibility that traffic DOESN'T stall at all but the PPP server is not responding to all LCP echo requests properly, in which case we are preventing an unnecessary drop of the connection.

I would also like to ask @Origin_Pete if you have any opinion on this? Are you aware of any reason why the PPP servers wouldn't be responding correctly to LCP echo requests?

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26-05-2013, 07:41 PM
Post: #2
RE: PPP dropping regularly? I may have solved it.
yes you are masking the problem and this is something I raised with Ripwire at the time

most routers will be set for 3 echo requests every 20 seconds, so the connection is checked 3 times every minute

I remember being told that failure to respond to the lcp echo requests would not cause the connection to drop (I also remember me having to explain how the lcp echo request/failure worked)

They also thought that a connection dropping for such a short period of time was nothing be worried about (even when advised this can cause issues when making financial transactions, streaming content, online gaming) - they never took into account that the reset of the line by router would be about 6-10 seconds, but the connection had already stalled/ceased as so could be up to a minute of downtime in total.

TBH I wouldn't mask the problem as Digital Region need to sort it out and really look it into and fix the problem, instead of just wiping it under the carpet hoping it will go away

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27-05-2013, 12:38 AM (This post was last modified: 27-05-2013 12:47 AM by alexatkin.)
Post: #3
RE: PPP dropping regularly? I may have solved it.
But that is what my final point is about, is the whole connection going dead for more than 6 seconds or is it just the server is failing to respond to echo requests for 6 seconds?

There is a big difference there as the former is potentially a serious problem, if the latter it can safely be ignored as it would have no detrimental effect on the broadband.

Obviously what I need to do is figure out some way to monitor the connection for 100% packet loss, you can't figure that out from the ping monitor unless it lasted minutes. I do have ping tests running from the router itself so I may already have all the information I need to check this but I need to write a script to parse the logs.

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27-05-2013, 11:03 AM
Post: #4
RE: PPP dropping regularly? I may have solved it.
When I had smoothwall running it was set to constantly test 3 addresses to determine if link went down

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27-05-2013, 05:13 PM
Post: #5
RE: PPP dropping regularly? I may have solved it.
But did you force the PPP daemon to not drop as it would only really prove anything if PPP was still up and there was packet loss.

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27-05-2013, 06:41 PM (This post was last modified: 27-05-2013 06:43 PM by mirdragon.)
Post: #6
RE: PPP dropping regularly? I may have solved it.
I changed numerous settings for LCP but the connection still dropped

TBH I,m surprised at the intervals you are using - as usually the interval is 20 seconds and the failures are 3

On your original settings you were doing a check every second, which would have resulted in the line being reset after 6 seconds. With your changes it's now 50 seconds, now if you consider I had mine set to 20/3 then mine was detecting after the minute the link had dropped or gone stale for no reason.

Ripwire even tried blaming it on me setting the timeout to '0' on the router and wanted it setting to 15 seconds - Don't think they appreciated it when I said '0' was to disable the disconnection and you cannot set it to 15 seconds and if you could then the line would drop without failure.

As we discussed on SF to be able to prove anything you need hard proof and for your ISP to listen, hopefully Origin will listen and help resolve the problem unlike Ripwire who dismissed it and said we should put up with the disconnections or pay an extortionate amount to get a business leased line from them. Ideally as the NOC are aware of all disconnections on the network then I would have expected them to look into why this is happening

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28-05-2013, 12:54 AM
Post: #7
RE: PPP dropping regularly? I may have solved it.
The NOC will only be aware if its a NOC issue causing packet loss. If this is an issue with the PPP server I doubt the NOC would know about it as I believe the PPP server belongs to the ISP, NOC are just responsibly for routing the traffic to the ISP.

Its interesting you mentioned such high values, it seems OpenWRT had incredibly low defaults which matches other PPP settings that completely failed to work on Origin. When I upgraded to the newer builds I had to modify the PPPoE connect script before it would work at all, it was not waiting long enough for a response to an authentication request. So it raises the question again if I actually have a problem at all or was it just a fault with the routers default configuration. You already said that in your case you couldn't prevent the problem with ANY settings, so it seems your reason for PPP dropping was different to mine.

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28-05-2013, 09:19 AM
Post: #8
RE: PPP dropping regularly? I may have solved it.
According to Ripwire, they reckoned the NOC were able to see the disconnections as the traffic stopped - also at the time they admitted others were experiencing the same problem.

Information supplied from 2011
Quote:From our logs we simply see your equipment drop off. We have found another customer that seemed to be affected at the same time which points to some further issue on the DRL network causing this.

We have been monitoring your connection as well as two others that are suffering similar issues and we have ruled out anything on our network, and as much as possible we have ruled out customers equipment based on their (your) feedback. This leads again to the assumption that it must be something within the DRL access network itself that is causing this issue.

The VDSL Cellpipe modems do carry a log but it is only viewable by Thales/DRL.

Currently Thales does not keep logs for more than a week or so, as they are used for connection problem diagnosis only

Hopefully Thales now keep logs for longer and thus should see what is happening, the problem is if no-one is reporting issues then nothing will get done

But I would set your LCP settings to 20/3 and see how it goes, if continues to drop then you can feed that back to Origin. I don't think this is a fault of Origin's, but unless someone kicks Thales/DRL backside I don't think anything will be done about it for the foreseeable future

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28-05-2013, 08:12 PM (This post was last modified: 28-05-2013 08:13 PM by alexatkin.)
Post: #9
RE: PPP dropping regularly? I may have solved it.
That is interesting as I know this was the theory we had from the start but I hadn't realised Ripwire had confirmed it with yourself, I thought we were still guessing.

Like I said though, I'm not convinced either way when it comes to my own connection as I would expect the PPP server to drop the connection if it was packet loss on the Digital Region network itself. That said, I checked my ping logs and I did see 80-100% packet loss a few times over the last 30 days (each entry is the result of a 60 second ping command), which does suggest traffic stopped going over the PPP link even if the link itself stayed up.

I am reluctant to pursue this further as its not really causing me any problems. I'm not convinced the packet loss shown above was anything to do with the connection to the ISP as Origin has been a bit twitchy over the last 30 days, it could easily have been ISP maintenance.

For the record, my VDSL link has now been up 54 days 3 hours 40 minutes 15 seconds and PPPoE for 29 days 20 hours 24 minutes, and the last PPP disconnection was forced due to me changing the LCP settings.

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31-05-2013, 01:14 PM
Post: #10
RE: PPP dropping regularly? I may have solved it.
There are short periods where traffic seems to just stop somewhere between a customer tail and the ISP hand off point which manifests itself in PPP sessions dropping. We've seen the same behaviour when just using IP over Ethernet as well, no PPP involved.

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