Re: [IPv6] I-D Action: draft-ietf-6man-rfc6874bis-06.txt

[Shang Ye <[e-mail]>]

Jürgen & Brian,

On 2023/4/7 15:26, Jürgen Schönwälder wrote:

> In other words, why not simply use the
> following approach:
>
>    extract ZoneID characters
>    try to parse them as a numeric zone identifier
>    if succcess, done
>    otherwise try to parse them using if_nametoindex()
>    if success, use the index
>    otherwise report failure (or try any future zone name to index mapping function)

 From my experience of writing a URI parser, I can tell that this is 
indeed the right way of parsing a zone identifier. Should we probably 
mention this process in the document?

> What is the rationale for limiting the focus on human readable
> strings?  Why not generally support numeric zone indexes as they
> should always work and accepting zone names (oops interface names used
> as zone names) where this is feasible (i.e., the names use lowercase
> unreserved characters)? If we generally support numeric zone indexes,
> we would not have to exclude so called "infrastructure devices" since
> they should be able to deal with numeric zone indexes as well.

Aren't numeric zone indices already supported in the current format 
because they are exactly human readable strings? Section 11.2 of RFC 
4007 also says:

    An implementation SHOULD support at least numerical indices that are
    non-negative decimal integers as <zone_id>.

So I don't understand why this sentence is necessary:

    However, in some operating systems it is possible to use the
    underlying interface number, represented as a decimal integer, as an
    alternative to the human-readable string.

On the other hand, the following sentence is mostly true:

    For example, on Linux, a user can determine interface numbers simply
    by issuing the command "ip link show" and then, for example, use
    "fe80::1%5" instead of "fe80::1%Ethernet1/0/1", if the interface
    number happens to be 5.

Except that we can't really make a network interface name on Linux 
contain slashes, can we?

Now that users can work around their inability to use an unsupported 
interface names in a URI by first converting them into numerical 
indices, is it possible that we replace the ZoneID ABNF rule with

    ZoneID = 1*( %x61-7A / DIGIT / "-" / "." / "_" / "~" )

and thus avoid the case-sensitivity issue of zone identifiers altogether?


Regards,
Shang