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HN Dropping Packets [message #3886]

Thu, 22 June 2006 19:26

HaroldB
Messages: 61
Registered: June 2006

Member

Hello, My HN seems to be dropping some packets (1-5%) on occassion to the VPS. When tracerouting from the net, I see * on the HN route sometimes. The HN is not out of memory and the VPS beancounters has no failcounts. I do see this many times in dmesg:

Out of socket memory

I feel that this thread may hold useful information to me, but it is written in Russian. Can someone tell me if this describes my symptom and problem?

http://forum.openvz.org/index.php?t=msg&goto=1899&&a mp;srch=Out+of+socket+memory#msg_1899

Thank you
Harold P. Bogwaters

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Re: HN Dropping Packets [message #3895 is a reply to message #3886]

Fri, 23 June 2006 05:46

Vasily Tarasov
Messages: 1345
Registered: January 2006

Senior Member

The message "Out of socket memory" appears in the following cases:

1) (The number of orphaned sockets in VE) >= 1/4 * (numtcpsock.barrier)

2) (The number of orphaned sockets in VE) > (sysctl's net.ipv4.tcp_max_orphans)

3) More sophisticated "memory" condition.

You can use google to find out what are orphaned sockets and why they appear.

Then you can increase numtcpsock barrier and sysctl's net.ipv4.tcp_max_orphans, if you wish.

The number orphaned sockets in the system you can see in
/proc/net/sockstat.

Hope this help!

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Re: HN Dropping Packets [message #3913 is a reply to message #3886]

Fri, 23 June 2006 16:02

HaroldB
Messages: 61
Registered: June 2006

Member

Thanks for the info. Would this condition cause the HN to drop packets destined for VPS?

Since I am seeing dropped ICMP packets, could the number of orphaned tcp sockets have anything to do with the problem? What else could cause ICMP packets to be dropped on the HN en route to the VPS?

Harold

[Updated on: Fri, 23 June 2006 16:09]

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Re: HN Dropping Packets [message #3917 is a reply to message #3913]

Fri, 23 June 2006 19:14

dev
Messages: 1693
Registered: September 2005
Location: Moscow

Senior Member

do you have lost packets between host system and a VPS?

Most probably the reason is inside your network. I experienced some situations when a bad cable or a broken switch could cause similar effects. In this case you will have lost packets both when accessing the host system or a VPS.

Lost packets can also be normal when traffic shaping is used. But I suppose this is not a case, right?

http://static.openvz.org/userbars/openvz-developer.png

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Re: HN Dropping Packets [message #3919 is a reply to message #3917]

Fri, 23 June 2006 19:16

HaroldB
Messages: 61
Registered: June 2006

Member

I was using some rules from http://wiki.openvz.org/Traffic_shaping_with_tc

I believe this may have caused the problem. I have removed them to verify. However, the limit (mbit/sec) for each IP which I enforced was not reached when the packets are being dropped. Are there any limitations to this which we should be aware of?

Harold

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Re: HN Dropping Packets [message #3961 is a reply to message #3919]

Mon, 26 June 2006 08:12

dev
Messages: 1693
Registered: September 2005
Location: Moscow

Senior Member

There should be no limitations with TC. But in each particular case you need to get into details to understand why it drops packets. You need to monitor the traffic and make sure it really does not saturate your TC rules.

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