Wireshark-users: Re: [Wireshark-users] Retransmission because of no ACK from user

From: Martin Visser <martinvisser99@xxxxxxxxx>
Date: Mon, 17 Jan 2011 22:31:10 +1100
Is there an actual problem to be solved or are you just curious.
Retransmissions aren't all that unusual. If there is fluctuation in
round-trip-time as measured by TCP, then the TCP retransmission timer
might expire more often than you would like. Hence you will get
retransmissions.

Regards, Martin

MartinVisser99@xxxxxxxxx



On 17 January 2011 18:12, vincent paul <amoteluro@xxxxxxxxx> wrote:
> Thank you for the response.  user did receive the packet twice.  This is the
> reason why wireshark label the second packet as retransmission.
>
> regards,
>
>
> ________________________________
> From: Andrew Hood <ajhood@xxxxxxxxx>
> To: Community support list for Wireshark <wireshark-users@xxxxxxxxxxxxx>
> Sent: Sun, January 16, 2011 3:27:24 AM
> Subject: Re: [Wireshark-users] Retransmission because of no ACK from user
>
> vincent paul wrote:
>> Hi All,
>>
>> I am looking at one trace with retransmissions from server because user's
>> side
>> did not send ACK for packets it received from server.  Is there any reason
>> why
>> user's side does not send out ACK.
>
> Do you know the client did receive the data or is that an assumption?
>
> What is between the server and the client?
>
> Can you sniff the traffic at intermediate points?
>
> Do you see the session setup packets (SYN, SYN+ACK, ACK) and then when
> the data starts, the ACKs stop?
>
> This could be the classic "firewall dropping ICMP frag required packets"
> behaviour.
>
> Can you reduce the MTU at the server? In Windows you have to reduce it
> with a registry setting and that affects all interfaces and requires a
> reboot. Unixish systems let you set the MTU on route commands.
>
> If there is any ADSL involved, 1492 is a likely value for the MTU. 1460
> is the next most likely value.
>
> Andrew
> --
> There's no point in being grown up if you can't be childish sometimes.
>                 -- Dr. Who
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