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Topic # 13715 25-May-2007 11:26
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Hi all,

I've been having this strange problem for a few weeks but am unable to explain it (to the help desk people at least) and was wondering if anyone could give me any help?

The problem is that when someone starts to download a torrent it becomes impossible to view websites or do anything else on the internet. I looked and the torrents weren't even downloading just had a lot of connections open so they aren't using all the bandwidth. Also made sure nothing was being uploaded to saturate the connection but even when someone is not using torrents but has opened a lot of connections this happens.

I have a WRT54GL router and at first I thought it was a problem with NAT and the tables in the router getting full but this doesn't seem to be the case as it happens even when directly connected to the cable modem.

I have performed heaps of tracert's and the problem comes from what looks like my cable modem?

  1     1 ms     1 ms     1 ms  192.168.1.101
  2  1028 ms    45 ms    17 ms  203-97-105-1.cable.telstraclear.net [203.97.105.1]
  3    15 ms    10 ms    11 ms  ge-9-0-947.u22.telstraclear.net [218.101.61.50]
  4    19 ms    20 ms    24 ms  ge-1-2-0-819.ie1.telstraclear.net [203.98.23.1]
  5   128 ms   123 ms    95 ms  ge-0-2-0-1.xcore1.acld.telstraclear.net [203.98.50.251]
 .....

Every single time when I try to do a tracert while i am unable to do anything on the internet the 203-97-105-1.cable.telstraclear.net seems to have high latency and eventually it will come up with "No Route to Host - the my cable IP address" or something like this

Tracing route to www.blah.com [194.243.135.33]
over a maximum of 30 hops:

  1     1 ms     1 ms     1 ms  192.168.1.101
  2  <Cable modem address>.cable.telstraclear.net [<Cable modem address>]  reports: Destination host unreachable.

Trace complete.

I am able to reproduce this on every computer in our flat also.

Is this a problem with my cable modem? Or is something happening that I don't know about?

Thanks for any help.

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BDFL - Memuneh
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  Reply # 72189 25-May-2007 11:34
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Are you using Windows XP SP2? There's a known limitation of 10 open SYN connections per second with this system, as a "security" measure. It actually slow down things, but won't stop it.

To see if this is the case, open Event Viewer and look for Event ID 4226 while you are running your programs. If there's any event such as this, then it could be the cause of your problem.







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  Reply # 72190 25-May-2007 11:39
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freitasm:

Are you using Windows XP SP2? There's a known limitation of 10 open SYN connections per second with this system, as a "security" measure. It actually slow down things, but won't stop it.

To see if this is the case, open Event Viewer and look for Event ID 4226 while you are running your programs. If there's any event such as this, then it could be the cause of your problem.



Yep im using SP2 but have not seen any of those messages in my logs for years. I think I may have installed that patch to up the limit a while ago :) I have also tested this on my Linux server I had setup for a little bit and still get the same problem so I don't think I am running into that issue.

Is 203-97-105-1.cable.telstraclear.net my cable modem? Or is it some node/switch/router up the road or something?

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  Reply # 72192 25-May-2007 12:12
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ramon:

Is 203-97-105-1.cable.telstraclear.net my cable modem? Or is it some node/switch/router up the road or something?


Your cable modem does not have an IP address (at least not one that you can see). It acts as a layer-2 device---essentially an Ethernet switch if you like. 203.97.105.1 is the address of the gateway, that is, the first router that you connect to. It's one of the things you have to configure into your PC or your cable router. It's on the piece of paper the installer gives you, along with your PC's IP address and the DNS name server addresses.

That device intentionally gives very low priority to PING (i.e., it will get around to it when it has nothing better to do), so using PING to the gateway tells you very little about latency. The number in fact is obviously bogus since the subsquent hops have a lower latency than the gateway, according to PING and traceroute.

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  Reply # 72195 25-May-2007 12:30
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Is the modem connected directly to the computer, or do you have something else like a router/switch between them?




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  Reply # 72211 25-May-2007 14:38
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michaeln:
ramon:

Is 203-97-105-1.cable.telstraclear.net my cable modem? Or is it some node/switch/router up the road or something?


Your cable modem does not have an IP address (at least not one that you can see). It acts as a layer-2 device---essentially an Ethernet switch if you like. 203.97.105.1 is the address of the gateway, that is, the first router that you connect to. It's one of the things you have to configure into your PC or your cable router. It's on the piece of paper the installer gives you, along with your PC's IP address and the DNS name server addresses.

That device intentionally gives very low priority to PING (i.e., it will get around to it when it has nothing better to do), so using PING to the gateway tells you very little about latency. The number in fact is obviously bogus since the subsquent hops have a lower latency than the gateway, according to PING and traceroute.


Aha that was my problem :) When the cable guy installed it a few months back he only left me the IP address and not the gateway address. So naturally I assumed that the IP address was the gateway address as well ... so now I changed the gateway to 203.97.105.1 and it seems to be working correctly now. Can't believe I missed that.

It kind of makes sense now, and i guess that something along the line was getting confused and causing the problem.

Thank you very much your help :)

Cheers,
Ramon.

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