[multipathtcp] Question on Data Sequence Mapping

Rao Shoaib <rao.shoaib@oracle.com> Tue, 16 May 2017 00:41 UTC

To: "multipathtcp@ietf.org" <multipathtcp@ietf.org>
From: Rao Shoaib <rao.shoaib@oracle.com>
Message-ID: <2a1aa330-f004-577e-93b4-0c93726e33d9@oracle.com>
Date: Mon, 15 May 2017 17:39:12 -0700
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Subject: [multipathtcp] Question on Data Sequence Mapping
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Hi,

Section 3.3.1 of RFC 6824 says

The data sequence mapping specifies a mapping from subflow sequence 
space to data sequence space. This is expressed in terms of starting 
sequence numbers for the subflow and the data level, and a length of 
bytes for which this mapping is valid.

<...>

A mapping is fixed, in that the subflow sequence number is bound to the 
data sequence number after the mapping has been processed. A sender MUST 
NOT change this mapping after it has been declared;

Does it mean that I can not map the data sequence to another (higher) 
TCP sequence number on the same flow.

The reason I am asking this is that if this is allowed  TCP and MPTCP 
processing can be separated on the recv side. For example, TCP could 
accept the packet but MPTCP could reject it. Since data level ack would 
not be sent the peer would retransmit, possibly using the same flow but 
with a different mapping so that TCP would accept the packet.

Is this legal to do and if not than why ?

Regards,

Rao

[multipathtcp] Question on Data Sequence Mapping Rao Shoaib
Re: [multipathtcp] Question on Data Sequence Mapp… Rao Shoaib
Re: [multipathtcp] Question on Data Sequence Mapp… Mark Handley