Subject: [tsvwg] One more edit for draft-ietf-tsvwg-ecn-experimentation-01

From: Bob Briscoe <[email-masked]>
Date: Wed, 19 Apr 2017 13:54:49 +0100

David,

At the end of Section 4.3 
<https://tools.ietf.org/html/draft-ietf-tsvwg-ecn-experimentation-01#section-4.3>, 
there ought to be a reason for why there's a SHOULD NOT rather than a 
MUST NOT:

CURRENT:
    therefore RFC 3168 is updated by adding the following text to the end
    of Section 6.1.1.1 on Middlebox Issues:

       Unless otherwise specified by an Experimental RFC, middleboxes
       SHOULD NOT discard TCP control packets and retransmitted TCP
       packets solely because the ECN field in the IP header does not
       contain Not-ECT.
ADD:
    The previous sentence says "SHOULD NOT" rather than "MUST NOT"
    because one potential exception is envisaged.  A security function
    that has detected an ongoing attack MAY drop more ECT marked SYNs
    than not-ECT marked SYNs.  Such a policy MUST NOT be applied
    routinely.  It can only be applied if an attack is detected, and
    preferably only if it is determined that the ECT capability is
    intensifying the attack.
REASONING:
The "SHOULD NOT" is not meant to be an open invitation for middleboxes 
to do what they choose. It would have been a "MUST NOT" were it not for 
the possibility of middleboxes having to deal with ECN-specific attacks.

We had these two paras in draft-bagnulo-tcmp-generalized-ecn, but now 
that you have the first para in ecn-experimentation, we have taken them 
out. However, we're hoping you'll include something like the 2nd para too.

Regards

Bob

-- 
________________________________________________________________
Bob Briscoe                               http://bobbriscoe.net/