Subject: [tcpm] Followup for new rev of draft-ietf-tcpm-fastopen-06

From: Gorry Fairhurst <[email-masked]>
Date: Wed, 05 Feb 2014 18:50:44 +0000

Thanks for preparing this. I see that most of the comments and questions 
I raised in WGLC, have now been either addressed on the WG list or in 
the new revision of the draft.

https://datatracker.ietf.org/doc/draft-ietf-tcpm-fastopen/

I have four questions that people may be able to help me answer (and 
some comments that may easily be addressed, which I'll send separately).

Gorry

-----

1) Big MSS.
Section 4.1.3.
/Therefore the client MAY limit the cached MSS to 1460 bytes./
- The draft says the client MAY limit the cached MSS size.
- I've been thinking on this, and I am still not sure why you'd want to 
cache a larger value, since the implications are significant from 
getting this wrong, and the gains will often be minor. Do others think 
this needs to be written as MUST or perhaps a /SHOULD limit the cached 
MSS to 1460 bytes/???

2) Recommending periods
Sections 4.1.3.1 and 4.2.1
At least two points in the draft, it describes temporarily disabling TFO 
for a period of time. No real guidance is provided on how long this 
should be for - is any guidance needed? … Or are people happy with this, 
given any suitably large value is "safe"?

3) Cookie-less Fast Open (further research)
Section 7.2
/Disabling cookies simplifies … as the client no longer needs to request 
a cookie/
- I can see the server-side argument as described, but the client-side 
is not yet clear at all to me. This kind of suggests a slim client that 
can ignore things and still use TFO, but how would a client know this 
was safe to use?  I commented in the WGLC that I do not buy this, and 
suggested we draw attention to the fact that clients may "still need a 
method to detect conditions where TFO should not be used due to path 
properties."

4) Use in combination with IW=10?
Section 4.2.2 Receiver bullet 6; or in Section  7.3
- Finally, I didn't see any added discussion of IW=10 and its relevance, 
or not, to be used in combination with TFO. This was a point raised by 
more than me on the list. What are the thoughts of the group on allowing 
TFO in combination with the experimental IW=10 specification?