Re: TCP Previous segment lost, TCP dup ACK

[Thomas Ellingsén <Thomas.Ellingsen () crosskey se>]

Hi Martin,

Ok, I agree. But the thing that confuses me is the dup ACK that is ”requesting” the fast retransmission is comming from 
10.32.22.90 and the dup acks are always post a ” TCP Previous segment lost” originated from 192.176.3.132 witch in my 
mind indicates that 192.176.3.132  is missing a packet sent from 10.32.22.90.

Someone please enlighten a lost ”networker”!

Regards,
Thomas

From: Martin Visser [mailto:martinvisser99 () gmail com]
Sent: den 19 april 2010 15:27
To: Community support list for Wireshark
Subject: Re: [Wireshark-users] TCP Previous segment lost, TCP dup ACK

I'd pretty certain that this 10.33.22.90 hoping to invoke Fast Retransmit - http://en.wikipedia.org/wiki/Fast_retransmit

Regards, Martin

MartinVisser99 () gmail com<mailto:MartinVisser99 () gmail com>

On Mon, Apr 19, 2010 at 11:10 PM, Thomas Ellingsén <Thomas.Ellingsen () crosskey se<mailto:Thomas.Ellingsen () crosskey 
se>> wrote:
Hi,


I get TCP Previous segment lost folowed by 2-10 TCP Dup ACK

3381    2010-04-19 12:33:55.284770      192.176.3.132   10.32.22.90     TCP     [TCP Previous segment lost] [TCP 
segment of a reassembled PDU]

3382    2010-04-19 12:33:55.286392      10.32.22.90     192.176.3.132   TCP     [TCP Dup ACK 3379#1] 56791 > 29900 
[ACK] Seq=1 Ack=269280 Win=254 Len=0 SLE=270296 SRE=270660

3384    2010-04-19 12:33:55.333856      10.32.22.90     192.176.3.132   TCP     [TCP Dup ACK 3379#2] 56791 > 29900 
[ACK] Seq=1 Ack=269280 Win=254 Len=0 SLE=270296 SRE=270723

3387    2010-04-19 12:33:55.478371      10.32.22.90     192.176.3.132   TCP     [TCP Dup ACK 3379#3] 56791 > 29900 
[ACK] Seq=1 Ack=269280 Win=254 Len=0 SLE=270296 SRE=270791

...

> From what I understand there is lost packets. Is there any way to see in what direction the packets are getting 
> dropped/lost?

Why is 10.32.22.90 sending the same ACK multiple times? Is "he" waiting for a response on the ACK?? It does not make 
sence to me.

Regrads,
Thomas

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