Re: [tcpinc] TCP's treatment of data in SYN packets

[Joe Touch <[e-mail]>]

FWIW, IMO the best wording would:

- start with the simplest case, i.e., NOT trying to optimize EDO to use
SYN data

- present the use of SYN data with EDO as an optimization
        that optimization might be a MAY or SHOULD, but not a MUST

Otherwise, you're needlessly complicating your spec for an optimization.

Joe

On 7/28/2016 6:53 PM, David Mazieres expires 2016-10-26 PDT wrote:
> How about the following wording?
>
>    A SYN segment containing an ENO option MUST NOT include a TCP Fast
>    Open (TFO) option [RFC7413].  However, TEPs MAY specify the use of
>    data in SYN segments to achieve similar benefits to TFO.
>
>    The last TEP identifier suboption in host A's SYN segment is the _SYN
>    TEP_.  The SYN TEP governs the use of data in A's SYN segment.  If
>    the SYN TEP's specification does not define the use of such data,
>    then host A's SYN segment MUST NOT contain data and host B MUST
>    discard any such data.  Host B must also discard data in A's SYN
>    segment if either the SYN TEP differs from the negotiated TEP or host
>    B disables encryption.
>
>    The use of data in B's SYN-ACK segment is governed by the negotiated
>    TEP.  If the negotiated TEP's specification does not define the use
>    of such data, then host B's SYN-ACK segment MUST NOT contain data and
>    host A MUST discard any such data.  Host A MUST also discard any
>    received SYN data if it disables encryption.
>
>    When a host discards SYN data, it MUST NOT acknowledge the sequence
>    number of the discarded data.  Rather, it MUST acknowledge the other
>    host's initial sequence number as if the received SYN segment
>    contained no data.
>
>    Regardless of the SYN TEP and negotiated TEP, host A MUST NOT include
>    data in a SYN-only segment when in mandatory application-aware mode.
>    Moreover, in the event that host B is an active opener (because of
>    simultaneous open), host B's SYN-only segment MUST NOT include data.
>
>    Using data in SYN segments deviates from TCP semantics and can cause
>    problems with middleboxes or non-compliant TCP hosts.  Hence, all
>    TEPs SHOULD support a normal mode of operation that does not make use
>    of data in SYN segments.  Moreover, implementations SHOULD employ SYN
>    data only if explicitly requested by the application or in cases
>    where such use is highly unlikely to pose problems.
>
> David