Wireshark mailing list archives
Re: Dup ACK #1
From: Martin Visser <martinvisser99 () gmail com>
Date: Thu, 1 Apr 2010 09:40:10 +1100
Vincent, You indicated that you are trying to "understand any problem when a customer using our application across Internet.". You need to describe more clearly what the problem you are seeing is for us to be able to help. Is it unreliable (not connecting/disconnecting) or slower throughput than expected, or some other error reported by the application or user.
From what you have described it seems like you probably have normal
congestion going on, and TCP is using one of the various mechanisms it has to recover from it. Without seeing a packet capture (probably you should be this at client and server end if possible) as well as an understanding of the network topology (is it LAN/WAN or Internet?) it is pretty hard to diagnose. Regards, Martin MartinVisser99 () gmail com On Wed, Mar 31, 2010 at 11:15 PM, vincent paul <amoteluro () yahoo com> wrote:
Hi Martin, I google around I found one people had the same problem(similar to mine at server side) with wireshark capture, but there was no resolution. Please take a look and give some thought. http://episteme.arstechnica.com/eve/forums/a/tpc/f/469092836/m/675009277831 regards, PV --- On *Wed, 3/31/10, Martin Visser <martinvisser99 () gmail com>* wrote: From: Martin Visser <martinvisser99 () gmail com> Subject: Re: [Wireshark-users] Dup ACK #1 To: "Community support list for Wireshark" <wireshark-users () wireshark org> Date: Wednesday, March 31, 2010, 1:37 AM Duplicate ACKs are pretty common when you have congested network. If the client is expecting more data and doesn't receive it in time 9maybe 250ms) then it will send another ACK in the hope that the data it is missing/waiting on will be resent. You haven't indicated what problem you are chasing. If you send a small sample capture that would be useful. Regards, Martin MartinVisser99 () gmail com<http://us.mc1114.mail.yahoo.com/mc/compose?to=MartinVisser99 () gmail com> On Wed, Mar 31, 2010 at 3:58 PM, vincent paul <amoteluro () yahoo com<http://us.mc1114.mail.yahoo.com/mc/compose?to=amoteluro () yahoo com>wrote:Hi All , I looked at two traces captured at user's side: one going thru proxy and one bypassing proxy and observed a lot of Dup ACK #1. Both traces are traffic of HTTP download's file from server. I have the following observations and could not find any explanation 1)Traffic going thru proxy: User always sent double ACKs (one ACK(len=0) and its Dup ACK #1(len=0) immediately). No Dup ACK problem from server side 2)Traffic bypassing proxy: server, most of the time, sent out double ACK (ACK(len>0) and its Dup ACK #1 (len=0)) with a time period. This means: Server---> user: seq=1000 Ack=210 len= 1460 Server----> user (dup Ack #1) seq=2460, Ack =210 len=0 . . . Normal TCP data transfer from server for a while(kind of frequency) , then Server sends out double Acks again. But there were also some time intervals, the data transfer from server looked normal without any double Acks from server In this case, no Dup Ack problem from user's side. I appreciate your help very much. regards, PV ___________________________________________________________________________ Sent via: Wireshark-users mailing list <wireshark-users () wireshark org<http://us.mc1114.mail.yahoo.com/mc/compose?to=wireshark-users () wireshark org>Archives: http://www.wireshark.org/lists/wireshark-users Unsubscribe: https://wireshark.org/mailman/options/wireshark-users mailto:wireshark-users-request () wireshark org<http://us.mc1114.mail.yahoo.com/mc/compose?to=wireshark-users-request () wireshark org> ?subject=unsubscribe-----Inline Attachment Follows----- ___________________________________________________________________________ Sent via: Wireshark-users mailing list <wireshark-users () wireshark org<http://us.mc1114.mail.yahoo.com/mc/compose?to=wireshark-users () wireshark org>Archives: http://www.wireshark.org/lists/wireshark-users Unsubscribe: https://wireshark.org/mailman/options/wireshark-users mailto:wireshark-users-request () wireshark org<http://us.mc1114.mail.yahoo.com/mc/compose?to=wireshark-users-request () wireshark org> ?subject=unsubscribe ___________________________________________________________________________ Sent via: Wireshark-users mailing list <wireshark-users () wireshark org> Archives: http://www.wireshark.org/lists/wireshark-users Unsubscribe: https://wireshark.org/mailman/options/wireshark-users mailto:wireshark-users-request () wireshark org ?subject=unsubscribe
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Current thread:
- Immediate ACK from server vincent paul (Mar 27)
- Re: Immediate ACK from server Martin Visser (Mar 27)
- Re: Immediate ACK from server vincent paul (Mar 27)
- Re: Immediate ACK from server Martin Visser (Mar 28)
- Re: Immediate ACK from server Martin Visser (Mar 28)
- Re: Dup ACK #1 vincent paul (Mar 30)
- Re: Dup ACK #1 Martin Visser (Mar 30)
- Re: Dup ACK #1 vincent paul (Mar 31)
- Re: Dup ACK #1 vincent paul (Mar 31)
- Re: Dup ACK #1 Martin Visser (Mar 31)
- Re: Immediate ACK from server vincent paul (Mar 27)
- Re: Immediate ACK from server Martin Visser (Mar 27)