[tcpm] rto-consider: "regularly" taking RTT samples

["Mark Allman" <[e-mail]>]

Hi Gorry!

Thanks for all the comments.  I am going to work through them and
hack on the document.  I am addressing a couple of the easier
comments today.  But, will address them all soon.

I-D>> In steady state the RTO SHOULD be set based on recent
I-D>> observations of both the FT and the variance of the FT.

Gorry> - I don’t think these are wrong, but I think the advice is
Gorry>   not very crisp for a BCP - how recent? How does this relate
Gorry>   to Comment 3?

The "recent" here is defined in requirement (2b), as you note.  So,
it isn't meant to be crisp here.  I can see two paths:

(1) Remove the word "recent" from here.  The overall point of
    guideline (2a) is really that the RTO SHOULD be based on
    observations---i.e., not statically set.  The notion of "recent"
    isn't hugely important here as it is concretely developed in
    (2b).

OR,

(2) We could leave the "recent" in (2a) with a forward reference to
    indicate we are not leaving this as nebulous somehow.  E.g.,
    "... recent observations---as defined below---of both ..." if
    folks think keeping this notion (colloquially) in (2a) is a good
    idea.

I am pretty indifferent to both options.

I-D>> FT observations SHOULD be taken regularly ...
I-D>>
I-D>> The notion of "regularly" SHOULD be defined as at least once
I-D>> per RTT or as frequently as data is exchanged in cases where
I-D>> that happens less frequently than once per RTT.

Gorry> - To me, reads as impossible RFC2119 text, is this a
Gorry>   definition or something else? or Designs are REQUIRED to
Gorry>   define ... etc.

I really can't parse the complaint here (which is probably because
you well explained it, but since I wasn't there the slide isn't
conveying that to me).  I don't see this impossibility you are
suggesting.

That said,

Gorry> I hope this actually is intended to be:
Gorry> FT observations SHOULD be taken be at least once
Gorry> per RTT or as frequently as data is exchanged in cases where
Gorry> that happens less frequently than once per RTT.

This is in fact the intent and I am happy to use those words.

allman