P.S. I'm quite aware that this has already passed the IESG,
but it will obviously have to be updated one day, so please
keep these comments in a safe place.

   Brian

Brian E Carpenter wrote:
In section 11.7:

The preferred format for literal IPv6 addresses in URL's are also
defined [12].


However, reference [12] (RFC 2732) will be obsoleted by
draft-fielding-uri-rfc2396bis-06, which includes the material
from 2732, plus correct ABNF, and is in IETF Last Call.

   ...When a user types the preferred format for an IPv6
   non-global address whose zone should be explicitly specified, the
   user could use the format for the non-global address combined with
   the preferred format.

   However, the typed URL is often sent on the wire, and it would cause
   confusion if an application did not strip the <zone_id> portion
   before sending.  Note that the applications should not need to care
   about which kind of addresses they're using, much less parse or strip
   out the <zone_id> portion of the address.  Also, the format for
   non-global addresses might conflict with the URI syntax [13], since
   the syntax defines the delimiter character (`%') as the escape
   character.


[13] is RFC 2396, which will be obsoleted by draft-fielding-uri-rfc2396bis

Actually there is no problem with the conflict, except that in a URI,
a percent sign has to be percent-encoded as %25. So zone_id 1 would
be represented in a URI as %251.

   Hence, this document does not specify how the format for non-global
   addresses should be combined with the preferred format for literal
   IPv6 addresses.


I'd want a URI syntax expert to check, but I'm not sure that
there is any problem with %251, %252, etc. It's ugly, but using
literal addresses is always ugly. The real question is whether there
would ever be any *need* to specify a zone_id in a URI.

As for the conflict issue with the URI format, it
would be better to wait until the relationship between the preferred
format and the URI syntax is clarified.


It is clarified by draft-fielding-uri-rfc2396bis.

...In fact, the preferred
format for IPv6 literal addresses itself has the same kind of
conflict.


No, it's a very different conflict. % is a global escape character
in URIs, which is why it has to be escaped itself as %25. The colons
in IPv6 addresses are simply delimiters. I think this sentence is
unnecessary.

   ...In any case, it is recommended to use an FQDN instead of a
   literal IPv6 address in a URL, whenever an FQDN is available.


Indeed.

    Brian


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