Re: [yang-doctors] YANG QUIC-LB model

[Martin Duke <[e-mail]>]

Hello all,

Thanks very much for your comments -- I was able to get the model to
compile.

To answer mbj's question, yes there should be no more than three items.

I look forward to requesting a full review when the model stabilizes a
little more. You have made this process relatively painless.

Martin

On Tue, Feb 2, 2021 at 12:26 AM Jan Lindblad <[e-mail]> wrote:

> Martin,
>
> Actually, I think the string length is "0 | 3 * N - 1" since each byte is
> encoded as two hex digits and a colon, except the last byte which is just
> two hex digits, as in "11:22:33:44". But I wonder, why do you need a
> configured value for the length at all? Would it not suffice that the
> operator configures the hex-string and let the system figure out the length
> based on that?
>
> I did a quick scan of your module. It has a lot of trivial issues (naming,
> mandatory, prefix, ...) that are easy to fix, but overall I think you've
> understood how to do this.
>
> Best Regards,
> /jan
>
>
>
> On 2 Feb 2021, at 08:56, Martin Björklund <[e-mail]> wrote:
>
> Hi,
>
>
> Martin Duke <[e-mail]> wrote:
>
> Hello yang-doctors,
>
> I don't know that this rises to the level of a full review, but the QUIC-LB
> draft (currently adopted by the QUIC WG) is basically a standard for
> configuration of QUIC Load Balancers and servers to work together. After
> much reluctance to take on a format I don't understand, I took a shot at a
> YANG model:
>
>
> https://github.com/quicwg/load-balancers/blob/yang/draft-ietf-quic-load-balancers.md
>
> (The YANG stuff is in an appendix near the end -- search for #yang-model).
>
> Before we talk about a full review where you labor to understand the data
> items, I'd appreciate an informal quick sanity check that I am doing this
> roughly correctly, as I have zero experience with YANG.
>
>
> I downloaded the module and ran it through a YANG compiler, and
> started to fix several minor syntactical errors (such as missing ";"),
> but then I ran into other issues that made it difficult for me to
> guess what you meant.  I suggest you ensure that the model compiles
> (there are a bunch of compilers available, e.g., pyang, yanglint, ...)
> and post it again.
>
> Some comments though:
>
> You have:
>
>       list cid-configs {
>         key "config-rotation-bits";
>
>         leaf config-rotation-bits {
>           type uint8 {
>             range "0..2";
>           }
>
> This means that there can only be max 3 entries in this list.  Is that
> what you meant?
>
>
> You also have:
>
>       typedef quic-lb-key {
>         type yang:hex-string {
>           length 16;
>         }
>       }
>
> The YANG statement "length", when given on a type "string", or derived
> from "string", operates on the number of characters in the string.  In
> this case, you probably what to limit the number of bytes represented
> by the hex-string.  Unfortunately, it is not possible in standard YANG
> 1.1 to do this.
>
> However, in this particular case it sort-of works, since the length of
> the hex-string is 2 * N + 1, where N is the number of bytes.  Hence,
> the length would be 33.  If you do this I suggest you explain this in
> the description statement.
>
> An alternative could be to drop the length statement and only explain
> it in the description statement.
>
> One other silly question: I have a field whose length depends on other
> fields. Can you give me an example on how to express this correctly? e.g.
>
> leaf foo-length {
>    type uint8
> }
>
> leaf foo {
>    type yang:hex-string {
>        length foo-length;
>    }
> }
>
>
> This is possible by using a "must" statement.  However, it has the
> same problem with the lexical value as above:
>
>  leaf foo {
>    type yang:hex-string;
>    must 'string-length(.) = 2 * ../foo-length + 1';
>  }
>
>
>
> /martin
>
> _______________________________________________
> yang-doctors mailing list
> [e-mail]
> https://www.ietf.org/mailman/listinfo/yang-doctors
>
>
>