Re: [tcpm] New version of TCP Option for Transparent Middlebox Discovery available

[Joe Touch <touch at ISI.EDU>]

Andrew Knutsen wrote:
> Joe Touch wrote:
>> Andrew Knutsen wrote:
>>   
>>>   Requests are only valid in SYN packets. They MUST NOT appear in other
>>>   segments and MUST be ignored when found outside of a SYN.
>>>     
>>
>> Does that mean that the option is ignored, or the segment?
>>   
> 
>         I think the concept of ignoring options is pretty well
> understood, but perhaps we can add a reference. This situation is
> slightly unusual, since TCP options, in the "classic" Internet model,
> are always ignored by intermediate nodes (no "deep inspection"). This is
> no longer the case though, so the semantics of "ignoring" IP options
> apply to TCP options (pass them along intact at intermediates), as well
> as the usual interpretation of ignoring a TCP option (skip over them at
> the endpoint). This is well established "art", so we didn't see the
> necessity of explanation...

It's not at all clear to me that the text makes it clear that this
protocol involves the participation of intermediate nodes. You're going
to need a lot more explanation of how that is expected to be handled,
esp. since intermediate nodes don't keep TCP states.

E.g.: you need to explain what intermediate nodes do for each message,
and whether they need to keep state (and if so, how it is established
and maintained). You also need clear indication about what the endpoints
do with these messages if they ever see them (are they stripped off, or
still there?).

Joe

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