Unexplained ADSL packet loss

C

CirclingTheSun

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Cape Town
I've been running 4mbit ADSL for a while now but recently it started to give me problems. Most of the time the connection works fine but I frequently experience periods of severe packet loss. The modem/router doesn't lose sync and it doesn't lose connection to my ISP. I ignored this in the hope that the problem will eventually resolve itself but after some weeks its still happening.

Initially I suspected that my router was acting up. So I borrowed one from a friend but the problem persisted. Then I tried different ISPs but the intermittent connections didn't go away. I then suspected the wiring in the house so I redid that. No luck.

I eventually got hold of Telkom and they reset the port. This didn't do anything so they sent out a guy earlier today. Of course he showed up while the connection was fine. He told me his laptop wasn't working so he couldn't test things from my side but he phoned up someone to test the line from the central office in Bellville. He reported that the SNR and the Attenuation was good and that he doesn't see a line problem. He suggested we lower the line speed to 2mbps to see if it stabilises :|

Currently my router is reporting an SNR of 18.2 downstream and 12.0 upstream and Attenuation of 43.0 downstream and 24.0 upstream. This is somewhat lower than what the guy at the CO reported earlier. Everything seems to be working fine however. BTW I'm 3km from the CO.

Now assuming everything is working fine up to the DSLAM and and that there are no issues at the ISP what could be causing this packet loss?

I'm not to clued up with what happens in between the DSLAM and the ISP but based on what I know about TCP/IP I'm suspecting some kind of congestion. During times of high packet loss the probability of reaching a local site is higher than reaching an international site. This leads me to think that congestion is leading to packet loss which signals hosts to shrink their TCP congestion window. Because local packets will have a lower RTT, as they will get to the upstream router first and make it into the interface buffer while international packets with higher RTT's will be likely to find the interface buffer full and get dropped.

I mentioned some of this to the Telkom guy but he wasn't to clued up on the higher level stuff. He said that it is possible that the DSLAM gets congested. Apparently there are a bunch of DSLAMs at the Bellville CO and that if the problem persists he could maybe get me plugged into another one.

Basically what I would like to know is what goes on between the DSLAM and the ISP that could cause congestion?
 
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I've been struggling with the same problem. I constantly get at least 3% packet loss sometimes spiking up to about 40%. I've had multiple technicians at my house. One of them even rewired most of my house. The last one that came to check things out said that there are just too many ADSL users in my area and that the cards at the exchange are getting too saturated. Hey, what do I know but if it is the case then I might just be SOL until they upgrade the cards. Maybe they'll upgrade them for the 10MBit switchover.
 
I've been getting something similar very recently as well. I haven't phoned up my ISP/Telkom yet to get it investigated further on their end as my problem isn't as severe as yours. Basically from once a minute to 10 times a minute, seems to depend on time of day, I will suddenly get severe packet loss for a second or two. The problem is easy to observe just running a ping www.google.com -t for a minute (the problem is local and international) and latency is all good, but there will be a bunch of timed out requests. Applications always recover, but it seriously affects gaming, as at best, once a minute I get a pretty severe "spike".
 
Yup, here as well. 4Mb ADSL with Belkin and Netgear routers with MWEB as ISP. Runs fine for a while and starts to drop packets everywhere. I heard that you can get better and a more stable throughput by using two Coke cans and a piece of fishing line. Thanks for nothing Telkom. :wtf:
 
Yep, I've had the same thing for 6 months now. It's not every day, but most. Almost always happens from 6pm onwards until about 11pm on weekdays and most of the weekend. Obviously this is when most users are online so I suspect congestion. It's nigh impossible to explain this to the retards at Telkom, obviously...
 
I also have packet loss but i've managed to nail it down to utorrent, when its on i get 1-15% packet loss even if ut isnt downloading anything, but its ok, cause ut only runs @ night
 
How did you manage to trace it to uTorrent? I have been experiencing similar packet loss and have also had the 'congested' response from Telkom. It made sense at it seems to predominantly be between 18:00 and 20:30 when all the facebookers are twitfacing.

Now I am wondering if GrabIt could be the cause of my woes.
 
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