Last Call Review of draft-ietf-tokbind-negotiation-10
review-ietf-tokbind-negotiation-10-genart-lc-kyzivat-2017-11-26-00

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Document: draft-ietf-tokbind-negotiation-10
Reviewer: Paul Kyzivat
Review Date: 2017-11-26
IETF LC End Date: 2017-11-27
IESG Telechat date: TBD

Summary:

This draft is on the right track but has open issues, described in the 
review.

Issues:

Major: 0
Minor: 1
Nits:  1

(1) MINOR:

Section 2 states the following requirement:

    ... it SHOULD
    indicate the latest (highest valued) version in
    TokenBindingParameters.token_binding_version.

But this doesn't state the precise meaning of "highest valued version". 
For example, if the supplied version is 3.5, what does it say about 
other versions supported? Presumably it covers 3.0...3.5. But what about 
lower major versions? I guess it must mean that 1.0...1.x and 2.0...2.y 
are also supported for some value of x and y. But *what* values of x and 
y? All that were ever defined? And what are the rules about versions 0.n?

This use of versioning implies that a particular discipline be followed 
for defining new major/minor version numbers, and for implementors. But 
no such discipline is described.

Additional text is needed to nail all of this down.

(2) NIT:

The Introduction says:

    The negotiation of the Token Binding protocol and key
    parameters in combination with TLS 1.3 and later versions is beyond
    the scope of this document.

while item (3) of section 3 says:

        This requirement only applies when TLS 1.2 or an older TLS
        version is used (see security considerations section below for
        more details).

Taken together these seem odd - the requirement only applies to the 
entire scope of the document!

Please consider if these are saying what you mean, and tweak the wording.