Date: Wed, 05 Apr 2000 14:34:38 -0500 From: venkat venkatsubra <venkats@austin.ibm.com> To: jayanth <jayanth@yahoo-inc.com> Cc: net@FreeBSD.ORG Subject: Re: Simultaneous close .... Message-ID: <38EB954E.80EBB6FE@austin.ibm.com> References: <20000404095017.B15820@yahoo-inc.com>
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Jayanth,
This case is discussed in Wright & Stevens Vol.2
of TCP/IP Illustrated - Excercise 29.5. The suggested
fix in the book is to remove the TH_FIN flag in
tcp_outflags[] for the tcp CLOSING state. Because,
the problem here was the retransmission of the FINs
from both ends after receiving the other end's FIN.
Venkat
jayanth wrote:
> I was testing b/w two 4.0 boxes and saw the following scenario.
>
> Server side
> -----------
> 10:14:41.260613 server.7000 > client.1136: P 1:101(100) ack 32001 win 65535 (DF)
> 10:14:41.260709 server.7000 > client.1136: F 101:101(0) ack 32001 win 65535 (DF)
> 10:14:41.652936 client.1136 > server.7000: F 32001:32001(0) ack 101 win 17520 (D
> F)
> 10:14:41.653075 server.7000 > client.1136: F 101:101(0) ack 32002 win 65535 (DF)
> 10:14:41.659388 client.1136 > server.7000: F 32001:32001(0) ack 102 win 17520 (D
> F)
> 10:14:41.659485 server.7000 > client.1136: . ack 32002 win 65535 (DF)
> 10:14:41.989824 client.1136 > server.7000: . ack 102 win 17520 (DF)
>
> Client side
> -----------
> 18:10:18.484731 server.7000 > client.1136: P 1:101(100) ack 32001 win 65535 (DF
> )
> 18:10:18.485193 client.1136 > server.7000: F 32001:32001(0) ack 101 win 17520 (D
> F)
> 18:10:18.490679 server.7000 > client.1136: F 101:101(0) ack 32001 win 65535 (DF)
> 18:10:18.490726 client.1136 > server.7000: F 32001:32001(0) ack 102 win 17520 (D
> F)
> 18:10:18.818621 server.7000 > client.1136: F 101:101(0) ack 32002 win 65535 (DF)
> 18:10:18.818626 server.7000 > client.1136: . ack 32002 win 65535 (DF)
> 18:10:18.818663 client.1136 > server.7000: . ack 102 win 17520 (DF)
>
> If I remember right the last two ACKS are not necessary during
> simultaneous close?
>
> jayanth
>
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