From: Hagen Paul Pfeifer <hagen@jauu.net>
To: Gabriel Beddingfield <gabrbedd@gmail.com>
Cc: netdev@vger.kernel.org
Subject: Re: Miscalculated TCP ACK ?
Date: Mon, 22 Aug 2011 19:58:43 +0200 [thread overview]
Message-ID: <20110822175843.GC3294@nuttenaction> (raw)
In-Reply-To: <CAPbw_hwQSXtmFSxK49jDDgF2LuG8=cu5t=ZjQ_aO7=M9fm9xeA@mail.gmail.com>
* Gabriel Beddingfield | 2011-08-22 10:34:14 [-0500]:
>I'm having trouble with a particular server via HTTPS. It appears
>that my local linux machines are sending incorrect ACK. However, I
>don't have enough expertise to know for sure.
>
>Using wireshark, the server sends:
>
> Transmission Control Protocol, Src Port: https (443), Dst Port:
>36015 (36015), Seq: 27658, Ack: 827, Len: 18
>
>Local machine replies:
>
> Transmission Control Protocol, Src Port: 36015 (36015), Dst Port:
>https (443), Seq: 827, Ack: 27677, Len: 0
>
>It appears to me that the ACK is off-by-one (should have been 27676).
No, it is absolutely correct: ACK -> last seen Seq plus one (27658 + 18 + 1):
RFC 793:
If the ACK control bit is set this field contains the value of the
next sequence number the sender of the segment is expecting to
receive. Once a connection is established this is always sent.
Cheers, Hagen
prev parent reply other threads:[~2011-08-22 17:58 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-22 15:34 Miscalculated TCP ACK ? Gabriel Beddingfield
2011-08-22 16:38 ` Eric Dumazet
2011-08-22 17:19 ` Daniel Baluta
2011-08-22 18:05 ` Gabriel Beddingfield
2011-08-22 18:49 ` Eric Dumazet
2011-08-23 0:41 ` Gabriel Beddingfield
2011-08-22 17:58 ` Hagen Paul Pfeifer [this message]
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