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

"Sargent, Matthew T. (GRC-LCA0)[Peerless Technologies]" <matthew.t.sargent@nasa.gov> Fri, 24 March 2017 12:52 UTC

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From: "Sargent, Matthew T. (GRC-LCA0)[Peerless Technologies]" <matthew.t.sargent@nasa.gov>
To: 王帅 <13211134@bjtu.edu.cn>
CC: multipathtcp <multipathtcp@ietf.org>
Thread-Topic: [multipathtcp] when and how is data-ACK responded?
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Date: Fri, 24 Mar 2017 12:52:30 +0000
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Subject: Re: [multipathtcp] when and how is data-ACK responded?
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Hi Wang,

> On Mar 24, 2017, at 2:25 AM, 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?


From Section 3 of RFC 6824:
Therefore, an MPTCP implementation receiving a duplicate ACK that contains an MPTCP option MUST NOT treat it as a signal of congestion.

My reading on this is that an MPTCP implementation will have the logic built in to avoid the behavior you are describing. Could anyone confirm or correct this?

Thanks,
Matt