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Re: [multipathtcp] when and how is data-ACK responded?

Alan Ford <alan.ford@gmail.com> Fri, 24 March 2017 23:54 UTC

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From: Alan Ford <alan.ford@gmail.com>
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Date: Fri, 24 Mar 2017 23:54:00 +0000
Cc: multipathtcp <multipathtcp@ietf.org>
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To: 王帅 <13211134@bjtu.edu.cn>
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Subject: Re: [multipathtcp] when and how is data-ACK responded?
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Hi Wang,

Data ACK is separate from subflow ACK. It exists purely to control the connection-level receive window; each MPTCP segment will contain a data ACK allowing the receive window to advance. Whilst you could certainly see the same data ACK sent as a “duplicate ACK” when the same value is sent, this will not necessarily trigger retransmission - this depends on the subflow-level retransmission. It’s implementation-specific as to when you may decide to retransmit, duplicating packets on a separate subflow.

Regards,
Alan

> On 24 Mar 2017, at 06:25, 王帅 <13211134@bjtu.edu.cn> wrote:
> 
> Hi,
> 
>    Data-ACK is independent with subflow-ACK which is responded by TCP layer, but when and how is data-ACK responded? I wonder whether discontinuous segments in data-level will trigger duplicate ACK, so fast retransmission will happen.If not, how to avoid this problem?
> 
> Best,
> 
> Wang Shuai
> 
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