Re: [6lo] Éric Vyncke's Discuss on draft-ietf-6lo-ap-nd-13: (with DISCUSS and COMMENT)

["Eric Vyncke (evyncke)" <[e-mail]>]

Pascal

Thank you for your prompt reply. I will clear my DISCUSS in a moment as you will change the text.

Agreed on all the points except for the 'nonce'. I know the concept of course but the sentence "was never used with this device" is still too strong IMHO. To comply, it would require to keep the history for ever... I would prefer a less stringent wording.

-éric

On 29/01/2020, 16:38, "Pascal Thubert (pthubert)" <[e-mail]> wrote:

    Hello Eric : )
    
    Many thanks for your review! I cc'ed SEC-DIR because we could really use their recommendation to solve some of your questions, more below.
    
    Please see below:
     
    > == DISCUSS ==
    > 
    > -- Section 4.4 --
    > The length of the reserved field is not specified. Or am I missing something
    > obvious ?
    
    I concatenated the reserved fields in the picture and declared it as 40 bits. 
    Also added the number of bits in the reserved fields of other structures.
    
    > ----------------------------------------------------------------------
    > COMMENT:
    > ----------------------------------------------------------------------
    > 
    > == COMMENTS ==
    > 
    > -- Section 4.2 --
    > While status is set to 0 when sending a NS, what is the expected behavior of a
    > receiver ?
    
    Changed to 
    "
    In NS messages it MUST be set to 0 by the sender and ignored by the receiver.
    "
     
    > -- Section 4.3 and 4.4 --
    > Why is the Pad Length field a 8-bit field while the actual padding will always be
    > less than 8 bytes. Suggest to make it a 3 or 4 bits field and extend the reserved
    > field.
    
    Actually I thought that if we want to extend the option in the future, it is better to indicate the length of the public key as follows:
    
       |     Type      |    Length     | Reserved|  Public Key Length  |
    
    Where:
    
    Public Key Length: 13-bit unsigned integer. The length of the Public Key field in bytes.
    Public Key:  A variable-length field, size indicated in the Public Key Length field.
           	     JWK-Encoded Public Key [RFC7517]
    >Padding:  A variable-length field completing the Public Key field to align to the next 8-bytes boundary.
    
    
    Works?
    
    
    
    > 
    > -- Section 6.1 --
    > About "Nonce option MUST contain a random Nonce value that was never used
    > with this device", how can it be done? Keeping a local history? Giving some
    > operational hints would bee welcome. Especially, when there are multiple 6LR in
    > the LLN: how can they synchronize the nonce?
    
    The nonce is used once, so there's no synchronization. A new pair is formed and exchanged at each validation.
    
    The nonce game used here appear to be common practice. Yes, there's usually a need of local history, and the fact that we get a nonce from both side, apart from guaranteeing that the result is effectively unique to both parties, also makes the chances for history to repeat very low. 
    
    CC'ing SEC-DIR: Please help: if there is a reference for that practice, what it takes to maintain a nonce, and why we have a nonce from both sides? Trying to reinvent that text does not look like a good idea for this draft.
    
    
    
    > 
    > -- References --
    > Is there a reason why the crypto algorithms RFC 7748 and 8032 are not
    > normative?
    
    Interestingly they are informational. So that would be a downref. 
    
    CC'ing SEC-DIR: Please help: should we make these refs normative? 
    
    
    > 
    > == NITS ==
    > 
    > -- Section 2.2 --
    > To be honest, I am not a big fan of simply announcing concepts and referring to
    > many other RFCs. Suggest to mention which terms and concepts are defined in
    > each document. Else, the current section 2.2 mostly forces the readers to read
    > all the references.
    
    Yes and they are really there as additional reading, not normative.
    I changed the text to 
    " The reader may get additional context for this specification from the following references"
    I also moved classical ND and SEND references to informational references.
    
    Works?
    
    > -- Section 6 --
    > s/may use a same Crypto-ID/may use the same Crypto-ID/ ?
    
    Done
    
    Many thanks again Eric!
    
    Let's see what SEC-DIR thinks
    
    And a very happy new year (in France we have till Jan 31st to send wishes 😉)
    
    Pascal