Re: [Cbor] CBOR-YANG representation of common types

[Carsten Bormann <[e-mail]>]

Hi Maria,

On 2023-11-14, at 17:54, Maria Matejka <maria.matejka=[e-mail]> wrote:
> 
> Dear CBOR WG,
> 
> we're currently trying to embrace the CBOR described by YANG in BIRD interface and we're struggling with the representation of certain types like date, time, IP address or prefix. We would assume that if there is RFC 9164 or RFC 8943, we shall then encode dates or IP addresses in these defined formats in CBOR and they shall get converted between CBOR and JSON/XML appropriately. But I can't find any RFC on this, nor any implementation of CBOR-JSON convertor.

These types are all defined as text string types in RFC 6991 etc. (and RFC 6991bis does not change anything about this).
RFC 9254 defines a basic representation of YANG in CBOR, not trying to change this.

> Thus, these questions arise:
> 
> 	• Is there any discussion on this topic, regarding interoperability between CBOR and JSON/XML?

This is a timely question.
There definitely is discussion, as the representation of these types as a CBOR text string is inefficient (with respect to both space and CPU time).

> 	• Is there any RFC on draft on this? If not, we're probably gonna create one. We need it

Writing up a proposal is on my to do list.
Right now I’m looking at:

     typedef object-identifier {
       type string {
     typedef object-identifier-128 {
       type object-identifier {
         pattern '\d*(\.\d*){1,127}';
     typedef date-and-time {
       type string {
     typedef phys-address {
       type string {
     typedef mac-address {
       type string {
     typedef hex-string {
       type string {
     typedef uuid {
       type string {
     typedef dotted-quad {
       type string {
     typedef ip-address {
       type union {
         type inet:ipv4-address;
         type inet:ipv6-address;
     typedef ipv4-address {
       type string {
     typedef ipv6-address {
       type string {
     typedef ip-address-no-zone {
       type union {
         type inet:ipv4-address-no-zone;
         type inet:ipv6-address-no-zone;
     typedef ipv4-address-no-zone {
       type inet:ipv4-address {
     typedef ipv6-address-no-zone {
       type inet:ipv6-address {
     typedef ip-prefix {
       type union {
         type inet:ipv4-prefix;
         type inet:ipv6-prefix;
       }
     typedef ipv4-prefix {
       type string {
     typedef ipv6-prefix {
       type string {

This can use tags from RFC 8949, RFC 9164, RFC 9090; we probably need to discuss little details such as whether tag 23 can be used for hex-string.

> 	• Is there any implementation of YANG-ed converter between CBOR and JSON? If not, we're probably gonna create one. We need it.

Laurent Toutain has a tool that extracts from a YANG module the parameter information needed for such a YANG-CBOR ⬌ YANG-JSON converter today.
This tool uses base types, so it cannot quite address the above list.
But the idea should be transferable.

Grüße, Carsten