excessive TCP duplicate acks?
Andre Guibert de Bruet
andy at siliconlandmark.com
Fri Feb 23 07:17:35 UTC 2007
On Feb 21, 2007, at 10:39 AM, Andre Oppermann wrote:
> Andre Guibert de Bruet wrote:
>> On Feb 20, 2007, at 2:31 PM, Andrew Gallatin wrote:
>>> Thanks for reporting this. I'm glad I'm not the only one who is
>>> seeing this!
>> I discovered this while testing out a new multi-homed bonded-T1
>> installation. I was wondering why I was getting no more than
>> ~170KB/ s. So far, here are the data points that I have gathered:
>> - It affects more than one type of NIC (em0).
>> - It happens regardless of hardware checksum enabled status.
>> - It happens independent of IP aliasing.
>> - I tested GENERIC as of Feb 19 and it is affected.
>> - A kernel from December 15th, 2006 exhibits this problem.
>> - The affected system is connected to a Linksys 24-port unmanaged
>> gigabit switch (I have the exact same hardware working just fine
>> with 5.5-STABLE on the same switch).
>
> Today I finally got some spare time and tried to track this down.
> However
> there is no obvious smoking gun to be seen. I'll dig further.
Andre,
Just as a followup to my off-list email: I have since come across
kern/102653. Though my setup uses stateful inspection rules
exclusively, the problem still persists with "allow ip from any to
any" as the single rule in ipfw. I have a pcap of the traffic
patterns that I am seeing, at http://siliconlandmark.com/staff/andre/
files/7-current_dupacks.pcap (2.3MB - This pcap was made with the
single allow any to any rule).
Andy
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