Latency oddity

Bill · Sep 27, 2013, 08:49:38

Been getting some odd results from the BQM:

Monday (for reference):

Tuesday:

Wednesday:

Thursday:

They're the IPv4 results, IPv6 are the same.

I can't see it on any other BQM to which I have access (IDNet or other) so it seems likely that it's at least semi-specific to my line/routing, it's not anything I've been doing at the time. I don't think it's interference from a neighbour's amateur radio transmitter (first thought), but I haven't been able to get hold of him to check and anyway I'd expect that to show in increased packet loss, not latency.

I haven't yet had the chance to run any speedtests whilst it's happening, but I haven't noticed any effect on normal browsing etc so it's not really serious, and as yet I can't know whether it's every day, weekdays only etc which might point to a local business or something hammering the exchange.

I'm currently running 24-hours' worth of pings to idnet.com, when it's finished I'll graph the results to see if it shows on outgoing pings, if it doesn't I'd assume it's something on the route to/from tbb.

Questions- is anyone else seeing anything similar (especially in my area, South Oxfordshire), can anyone suggest anything else it might be or other checks I can run? So far I'm just curious what might be causing it!

Kobe · Sep 27, 2013, 11:47:09

$:-\$

zappaDPJ · Sep 27, 2013, 11:59:10

I can find one BQM for Thursday that's almost identical to yours Bill. There's no packet loss, just an identical rise in latency which peaks around 10.00pm. For reference that's an ADSL 2+ connection located in Milton Keynes.

Bill · Sep 27, 2013, 12:16:11

@Kobe- There's noticeable packet loss on yours which I'm not getting, but the timing is too close to be coincidental... was it there on Tuesday and Wednesday, and whereabouts in the country are you?

@Zap- Thanks, not just me then... I've no idea of the route my connection follows, but MK isn't too far away. I'll keep an eye on it (I've set up another 24-hour ping session to bbc.co.uk) but still open to other ideas/suggestions!

Kobe · Sep 27, 2013, 16:08:35

@bill- yes it was the same on tuesday and wednesday and im from northumberland.

Bill · Sep 27, 2013, 18:51:47

Northumberland... that rather knocks out my idea that it might be congestion somewhere local(ish) to me then

Thanks.

Wooloff · Sep 27, 2013, 22:08:29

I don't know anything about packet loss and all this other tech stuff

I do a lot of online gaming and I've noticed that the 2 nights this week that I've played, tonight and Wednesday, that my pings in game have been a lot higher than usual.

I'm in Didcot, Oxfordshire. Pings are fine during the day, just seems to be in the evening/night.

Bill · Sep 27, 2013, 22:26:58

You're not far from me, certainly on the same exchange though I'm on FTTC... I don't do gaming so I don't usually notice ping variations very quickly. Packet loss is the red stuff at the top of the graph, and is what it sounds like- too much means trouble

My BQM has been OK tonight:

But there's something going on- most of the graphs I've linked to in this topic show periods when the latency drops by a millisecond or so for several hours then goes back up again. Maybe IDNet are switching the routing around (load balancing?) at intervals and (accidentally I hope!) dumped some of us on a busy route?

I'll have a closer look at my 24-hour ping records when they finish tomorrow, maybe they'll tell me something (tho' I'm not optimistic).

If anyone from IDNet reads this maybe they'd like to comment? It's not worth a support call afaic.

Wooloff · Sep 27, 2013, 22:46:58

I'm on ADSL2+ at the moment, keep thinking of moving to FTTC but that would probably mean moving to BT as well.

I'll keep an eye on my pings for the next week or so but with online gaming pings can make a huge difference, so a higher ping is not something I really want to have to put up with for too long a period

Bill · Sep 28, 2013, 08:59:09

Yes, I can understand that... my slight drop in ping time seems to have stayed for now but, like you, I'll keep a closer eye on things for a few days.

As expected, my 24-hour ping runs didn't tell me much apart from confirming the ping drop and that, when dealing with spreadsheets with the thick end of 100,000 lines, NeoOffice is very slow and has a tendency to crash on exit

I did find out one thing, though not relevant to this matter- ping gives me output like:

64 bytes from 212.69.36.10: icmp_seq=18 ttl=59 time=11.363 ms

the icmp sequence number is processed as an unsigned 16-bit integer and wraps around to zero at 65,536. Caused me a lot of head-scratching importing the file into the spreadsheet until I realised what was going on

cavillas · Sep 28, 2013, 12:45:22

Perhaps looking at this site https://btbusiness.custhelp.com/app/service_status_consumer/ss_cat/2468,2470 will give clues to some problems.

Steve · Sep 28, 2013, 16:38:56

I had some packet loss on Tuesday night and the DLM has upped the Interleave level on Thursday- not bad for a connection that's been unused all week while I've been away

Bill · Sep 28, 2013, 16:54:03

I suppose that, strictly speaking, the connection is only unused if your router is off- there's all sorts of traffic going backwards and forwards if you're connected.

And the BQM is definitely using it...

Steve · Sep 28, 2013, 18:36:26

True I suppose, but then I doubt that sort of traffic stresses the DLM. Anyways it usually returns to 'normal' in 2-3 weeks.

andrue · Sep 28, 2013, 21:35:27

Quote from: Steve on Sep 28, 2013, 18:36:26
True I suppose, but then I doubt that sort of traffic stresses the DLM. Anyways it usually returns to 'normal' in 2-3 weeks.

We had that discussion on TBB a while back. Can't find it at the moment but as I remember the conclusion was that DLM couldn't care less whether your line is carrying actual data or not. The modems at either end are always talking to each other and if your connection is idle it's just sending empty packets.

Kobe · Sep 28, 2013, 22:25:13

andrue · Sep 29, 2013, 12:14:52

Ah, found that thread:

http://forums.thinkbroadband.com/fibre/t/4231120-re-dlm-and-the-nte-modem.html

Specifically:

http://forums.thinkbroadband.com/fibre/t/4231225-re-dlm-and-the-nte-modem.html

"The datastream is broken down into frames, with framing and control data forming the structure. The modems are constantly monitoring that data to ensure that it can hear the other side - which can lead to the "loss of signal" event and a resync.

The same control bits are used for the modem to report back to the DSLAM any errors that it is seeing.

They're all constantly going back-and-forth.

The gaps between the framing/control data is where the end-user data goes. If there isn't anything to send, it is just empty rather than non-existent. I don't have my VDSL2 spec to say what empty actually is though."