Re: [Sip] Question regarding conflicting grammar for IPV6 SIP URI andRFC 3986

Brett Tate wrote:
> Intentional or not, the sip-uri (excluding IPv6reference) appears to not
> violate extending rfc2396's absoluteURI because the definition was a
> structured subset of opaque_part.  However the introduction of brackets
> to enclose an IPv6 address causes the sip-uri to no longer be a valid
> absoluteURI (rfc2396) or absolute-URI (rfc3986).

3986 accomodates IPv6 addresses within in "authority" which seems to 
serve roughly the same role as "[ userinfo ] hostport" in SIP-URI. But 
"authority" is always preceded by "//", so it doesn't work for sip.

To fit a sip uri within 3986 I think you must start with:

    URI           = scheme ":" hier-part [ "?" query ] [ "#" fragment ]

    hier-part     = path-rootless

    path-rootless = segment-nz *( "/" segment )

    segment-nz    = 1*pchar

    pchar         = unreserved / pct-encoded / sub-delims / ":" / "@"

    unreserved    = ALPHA / DIGIT / "-" / "." / "_" / "~"

Not only does the above exclude the IPv6 syntax, it also excludes lots 
of other things that are commonly used in the userinfo portion of sip URIs.

I don't know if this is of practical concern or not. The SIP URI is 
defined by 3261. Certainly 3261 didn't call for it to be compatible with 
3986. Yet it would be *nice* if it was for compatibility with software 
that treats URIs, including SIP URIs generically. But I don't know how 
important that is in practice.

To fit 3986 well, I think would have to aim for fitting into:

       URI         = scheme ":" hier-part [ "?" query ] [ "#" fragment ]

       hier-part   = "//" authority path-abempty

       authority   = [ userinfo "@" ] host [ ":" port ]

But that would require SIP-URIs like sip://alice@atlanta.com
and I don't think we are going to migrate to that any time soon.

Don't mailto URIs have similar problems? What are they doing about it?

	Thanks,
	Paul

> I'm currently not sure if a fix is really needed or how best to correct
> it.  Escaping the brackets might work; however that might cause more
> headaches.
> 
> 
>> -----Original Message-----
>> From: Vijay K. Gurbani [mailto:vkg@alcatel-lucent.com] 
>> Sent: Thursday, December 18, 2008 5:43 PM
>> To: Brett Tate
>> Cc: SIP@ietf.org
>> Subject: Re: [Sip] Question regarding conflicting grammar for 
>> IPV6 SIP URI andRFC 3986
>>
>> Brett Tate wrote:
>>> Greetings,
>>>  
>>> Mike's interpretation looks correct.  Is this something 
>> that should be 
>>> fixed?  If so, should the fix be placed within 
>>> draft-ietf-sip-ipv6-abnf-fix?
>> What should the fix be?  Mike's claim is that rfc3261 
>> violates rfc3986, yet rfc3986 is internally consistent in 
>> that it requires IPv6 literals to be enclosed in "[" and "]",
>> viz:
>>
>>     IP-literal = "[" ( IPv6address / IPvFuture  ) "]"
>>
>> At the same time, rfc3261 is internally consistent in that it 
>> requires IPv6reference to be enclosed in "[" and "]", viz:
>>
>>    IPv6reference  =  "[" IPv6address "]"
>>
>> Furthermore, I don't think the intent is to produce SIP-URI 
>> (as defined in rfc3261) from a URI (as defined in rfc3986), is it?
>> Note that rfc3986 defines URI as:
>>
>>    URI = scheme ":" hier-part ...
>>    heir-part = "//" ...
>>
>> If this was true, a SIP URI would need to be produced as:
>>
>>    sip://[2001:db8:10] ...
>>
>> In other words, I am trying to understand what the exact 
>> problem is before we try to figure out where to put the fix in...
>>
>> Thanks,
>>
>> - vijay
>> --
>> Vijay K. Gurbani, Bell Laboratories, Alcatel-Lucent 1960 
>> Lucent Lane, Rm. 9C-533, Naperville, Illinois 60566 (USA)
>> Email: vkg@{alcatel-lucent.com,bell-labs.com,acm.org}
>> Web:   http://ect.bell-labs.com/who/vkg/
>>
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