Re: [xmpp] draft-ietf-xmpp-address

[Bruce Campbell <[e-mail]>]

On Tue, 6 Jul 2010, Peter Saint-Andre wrote:

> On 7/6/10 6:34 PM, Peter Saint-Andre wrote:
>> On 6/29/10 11:47 AM, Bruce Campbell wrote:
>>
>>> Alternatively, the ABNF for the JID address draft could be brought into
>>> alignment with 3986 by specifying:
>>
>>>  2.1.
>>>   domain = fqdn / IPv4address / IP-literal
>>>            ; the "IPv4address" and "IP-literal" rules are
>>>            ; defined in RFC3986.
>>
>>> which would result in domainpart allowing a bare IPv4 address (
>>> foo@1.2.3.4/bar ), and IPv6 and other literal addresses needing to be
>>> enclosed in '[]' as per RFC3986 .
>>
>> Although I have never seen a domainpart consisting of an IPv6 address
>> (and have rarely seen one consisting of an IPv4 address), I think it
>> would be best to be consistent with RFC 3986 on this point.
>
> Looking at this more closely, I wonder if we could re-use the ihost
> definition from RFC 3987. That would yield:
>
>   jid            = [ localpart "@" ] ihost [ "/" resource ]
>                    ; the "ihost" rule is defined in RFC 3987
>
> where:
>
>   ihost          = IP-literal / IPv4address / ireg-name
>   ireg-name      = *( iunreserved / pct-encoded / sub-delims )
>   iunreserved    = ALPHA / DIGIT / "-" / "." / "_" / "~" / ucschar
>   ucschar        = %xA0-D7FF / %xF900-FDCF / %xFDF0-FFEF
>                  / %x10000-1FFFD / %x20000-2FFFD / %x30000-3FFFD
>                  / %x40000-4FFFD / %x50000-5FFFD / %x60000-6FFFD
>                  / %x70000-7FFFD / %x80000-8FFFD / %x90000-9FFFD
>                  / %xA0000-AFFFD / %xB0000-BFFFD / %xC0000-CFFFD
>                  / %xD0000-DFFFD / %xE1000-EFFFD
>
> and where the "IP-literal" and "IPv4address" rules are as in RFC 3896.
>
> This is a step in the right direction, because it appears (!) that the
> ABNF in RFC 3920 doesn't allow anything but letter-digit-hyphen (i.e.,
> nothing outside the US-ASCII range).
>
> However, ireg-name isn't quite right either because some its aspects
> (pct-encoded and sub-delims) are included for compabitility with URI
> syntax, and we don't need those in native JIDs.
>
> Thus we could do this:
>
>   jid            = [ localpart "@" ] domainpart [ "/" resourcepart ]

Do we need a comment about implementations identifying the localpart, 
domainpart and resourcepart portions before applying any transformations? 
A quick glance shows %x2215 (division slash) just lurking there for the 
implementer who applies ToASCII to the domainpart before picking out the 
resourcepart.

>   domainpart     = IP-literal / IPv4address / ifqdn
>   ifqdn          = 1*( iunreserved )
>                    ; the "iunreserved" rule is defined in RFC 3987
>
> I'm not an ABNF guru, so feedback is welcome.

Apart from personally disliking '~' and '_' in the domainpart, WFM.

You may want to add an additional comment pointing people to IDNA2003 or 
IDNA2008 for rules regarding "ifqdn"/"domain name slot" when used on 
public networks, eg:

   ; the "iunreserved" rule is defined in RFC 3987
   ; [IDNA-DEFS] defines additional rules for "ifqdn" if used on public
   ; networks; see "domain name slot" in that document.

-- 
   Bruce.