[97866] in North American Network Operators' Group
Re: TCP congestion
daemon@ATHENA.MIT.EDU (Leigh Porter)
Thu Jul 12 19:30:29 2007
Date: Fri, 13 Jul 2007 00:12:28 +0100
From: Leigh Porter <leigh.porter@ukbroadband.com>
To: Philip Lavine <source_route@yahoo.com>
CC: Stephen Wilcox <steve.wilcox@packetrade.com>, nanog <nanog@merit.edu>
In-Reply-To: <796919.42253.qm@web30811.mail.mud.yahoo.com>
Errors-To: owner-nanog@merit.edu
Come on folks, don't be afraid. We all know the beast is to blame for
this, just don't say the name three times...
Shub Internet
Philip Lavine wrote:
> I just don't understand how if there is 1 segment that gets lost how this could translate to such a catastrophic long period of slow-start. How can I minimize the impact of the inevitable segment loss/out of order over a WAN. Is QoS the only option?
>
> ----- Original Message ----
> From: Stephen Wilcox <steve.wilcox@packetrade.com>
> To: Philip Lavine <source_route@yahoo.com>
> Cc: nanog <nanog@merit.edu>
> Sent: Thursday, July 12, 2007 1:09:24 PM
> Subject: Re: TCP congestion
>
> Well, if its out of order its the same as if its lost or delayed, it needs to see that missing segment before the window is full
>
> As mentioned you need to get dumps from both ends, you will almost definitely find that you have packet loss which tripped tcp's slow start mechanism.
>
> Steve
>
> On Thu, Jul 12, 2007 at 12:02:49PM -0700, Philip Lavine wrote:
>
>> Even if the segment was received out of order what would cause congestion avoidance to starve the connection of legitimate traffic for 15 to 20 seconds? That is the core of the problem.
>>
>> ----- Original Message ----
>> From: Fred Baker <fred@cisco.com>
>> To: Brian Knoll <Brian.Knoll@tradingtechnologies.com>
>> Cc: Philip Lavine <source_route@yahoo.com>; nanog <nanog@merit.edu>
>> Sent: Thursday, July 12, 2007 11:56:06 AM
>> Subject: Re: TCP congestion
>>
>>
>> On Jul 12, 2007, at 11:42 AM, Brian Knoll ((TTNET)) wrote:
>>
>>
>>> If the receiver is sending a DUP ACK, then the sender either never
>>> received the first ACK or it didn't receive it within the timeframe it
>>> expected.
>>>
>> or received it out of order.
>>
>> Yes, a tcpdump trace is the first step.
>>
>>
>>
>>
>>
>>
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