Re: [Ace] Review draft-ietf-ace-coap-est

[Jim Schaad <[e-mail]>]

 

 

From: Peter van der Stok <[e-mail]> 
Sent: Monday, July 9, 2018 1:01 AM
To: Jim Schaad <[e-mail]>
Cc: [e-mail]; [e-mail]; 'ace' <[e-mail]>
Subject: Re: [Ace] Review draft-ietf-ace-coap-est

 

 

* In section 4.1 I have a question about what you are using for payload content encoding.  Part of this might just be a question of how you plan to move from ASN.1 to CBOR at some point in the future.  I think that it would necessitate doing new media-types in that event.  You appear to be doing a CBOR bstr wrapping on the ASN.1 encoding payload.  I don't believe that there is any reason for doing this.  I would expect that the payload would be the ASN.1 w/o any ASN.1.  It is highly possible that I am just mis-reading what the text says and this is what you say.

<pvds>

What I wanted to do, and did not express very well.

Keep the ASN.1 structure of the payload; (re-using code)

Use straight binary coding instead of the base64-encoded (30% payload reduction)

Wrap the binary in a CBOR major type 2 h'xxx' notation. (compatibility with multipart)

Not sure if this needs a new media type, the http content-coding and transfer-coding registries were not very helpful.

</pvds>

[JLS]  I do not believe that the wrapping of content with the CBOR binary text wrapping is needed at this point.  If that is needed for the multi-part wrapping, then it is the job of the multi-part wrapping to deal with this problem.  Multipart needs to be able to say I have a multipart of <plain text, json> neither of which are CBOR objects.  Therefor there is no reason for you to use a CBOR wrapper for this and not just use the binary value.

 


<pvds>
You are right of course, the CBOR wrapping is not needed outside the multipart media type.
However, CBOR wrapping for all payloads, reduces the choices when decoding the payload; They all start the same.
And it adds 2-3 bytes on many.
</pvds>

[JLS]  I don’t follow this at all.  How I read this statement is

I have a binary value and I need to look at the content type to figure out what ASN.1 structure it is and decode it.  This is very hard.  So I am going to change this to

I need to look at the content type to figure out that I have a CBOR bstring value.  It is easy to remove the CBOR bstring value.  I now have a binary value and I need to look at the content type to figure out what ASN.1 structure it is and decode it.  This is somehow easier.