Subject: Re: IPv6 address formats (rfc1884)

From: Brian E Carpenter <[email-masked]>
Date: Thu, 09 Nov 2000 09:07:38 -0600

Hi,

I have switched this to the IPNG working group list where it belongs.
(To join the list see http://www.ietf.org/html.charters/ipngwg-charter.html)

RFC 1884 is obsolete and replaced by RFC 2373, which itself is being
updated by the draft at 
http://www.ietf.org/internet-drafts/draft-ietf-ipngwg-addr-arch-v3-02.txt

However this does not really affect your question.

We have had some trouble in defining precise ABNF to include exactly
the formats we want and exclude those which make no sense. The ABNF 
we had was defective, so it has been removed from the latest draft.
If you can design  ABNF that is complete and correct it would be a 
valuable contribution. 

My opinion on your examples below:

Ramanan wrote:
> 
>   I want  some clarification on ip(v6) address representation.
> 
>   How do we treat the following addresses? Are they valid or
>   otherwise?
> 
>   1:2:3:4:5:6::7:8

Invalid. "::" is supposed to represent a string of zeros; in this case
it could only be a null string. But I could imagine writing a parser
that would accept this and treat it as equivalent to 1:2:3:4:5:6:7:8
That might be a good example of defensive programming.

>   ::1:2:3:4:5:6:7:8

Same.
>   0:0:0:0:0:0:1.2.3.4

Valid syntax. Equivalent to ::1.2.3.4

>   0::0:0:0:0:0:1.2.3.4

Invalid (same reason as above)

>   0:0:0:0:0:ffff:1.2.3.4

Valid syntax. There is an almost identical example in the draft.

>   0::0:0:0:0:ffff:1.2.3.4

Invalid (same reason as above)

Of course, valid syntax does not mean that the address is valid, but that
was not your question.

   Brian

> 
>   The rfc does not state if these are allowed.
> 
>   This clarification is important as some user scripts might
>   generate such ip addresses.
> 
>   An analogy I found is that most unix versions treat
>         /home/./ftp
>   same as
>         /home/ftp
> 
>   please getback to me suggestions?
> 
> Ramanan

-- 
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Brian E Carpenter 
Program Director, Internet Standards & Technology, IBM 
On assignment for IBM at http://www.iCAIR.org 
Board Chairman, Internet Society http://www.isoc.org
Non-IBM email: [email-masked]
--------------------------------------------------------------------
IETF IPng Working Group Mailing List
IPng Home Page:                      http://playground.sun.com/ipng
FTP archive:                      ftp://playground.sun.com/pub/ipng
Direct all administrative requests to [email-masked]
--------------------------------------------------------------------