Re: [core] I-D Action: draft-ietf-core-echo-request-tag-04.txt

[Carsten Bormann <[e-mail]>]

On Mar 24, 2019, at 01:27, [e-mail] wrote:
> 
> 
> A New Internet-Draft is available from the on-line Internet-Drafts directories.
> This draft is a work item of the Constrained RESTful Environments WG of the IETF.
> 
>        Title           : CoAP: Echo, Request-Tag, and Token Processing
>        Authors         : Christian Amsüss
>                          John Mattsson
>                          Göran Selander
> 	Filename        : draft-ietf-core-echo-request-tag-04.txt
> 	Pages           : 24
> 	Date            : 2019-03-23

Thank you!

I only have two editorial to semi-editorial comments (chairs-hat-off) about Section 5, which can be handled during the WGLC:

— I don’t know how to formally prove that a counter is “easiest”.  So I would probably avoid the absolute.  Calling out more explicitly what scope that counter has (I.e., the messages covered by the matching rule) might help, too.

— I don’t understand the comment about length-value coding.  There already is a length that governs the token.  The encoding informally described as “o256” in Appendix A.4 of draft-bormann-coap-misc-27.txt works well for me.  Maybe you mean that.  (Feel free to copy-paste that appendix.)

Grüße, Carsten

      # byte strings lexicographically goedelized as numbers (one+256 coding)
      def o256_encode(num)
        str = empty_buffer
        while num > 0
          num -= 1
          str << (num & 0xFF)
          num >>= 8
        end
        str.reverse
      end

      def o256_decode(str)
        num = 0
        str.each_byte do |b|
          num <<= 8
          num += b + 1
        end
        num
      end