Subject: RE: Scope ID secret Cabal (minutes)

From: Brian Zill <[email-masked]>
Date: Thu, 16 Dec 1999 09:51:26 -0800

> 1. Should the delimiter be placed before an address or after an
>    address?
> 
> We prefer "after an address", because

We prefer before an address because:

1) People already put other things after an address, like "/64" to indicate
that it's a prefix of some length, or @23 to indicate a port number.

2) I believe a scope id is logically the most significant part of an
address, and IPv6 addresses are inherently big-endian.

As for your reasons for putting it before:

> - we'd like to allow a user to omit a zone ID (and the delimiter) if
>   it is obvious (e.g. in a single-interface host).

You can do this just fine regardless of where the scope id is.  It's just as
readable either way.  I don't think this matters.

> - As I said in my earlier mail, I'm not sure if zone IDs should be
>   considered as the most significant part of scoped addresses.

We'll just have to disagree on that one.

> 2. Which charater (or strings) is the best as the delimiter?
> 
> We prefer a symbol character (i.e. not an alphabet character 
> or a word) for readability, and have considered several
> characters.

I think the important conflicts to worry about are the ones where something
using one of those characters is a legal value for an address, or a common
string that contains an address.  So I think ":", "@", and "-" are out.

Personally, I like "/", since it is already used (when placed at the end of
an address) to indicate a prefix length, so people are already familiar with
the situations in which they need to quote it.

Thus 3/fe80::200:86ff:fe39:40e9 would be interface #3 on my laptop here.

> 3. What is the appropriate synatx for zone IDs?
> 
> Numeric identifiers must be provided. Also, if the system provide
> interface names (like `le0' or `etherne1'), the names may be used as
> (non-numeric) identifiers.
> In any case, zone IDs should be composed by numbers and alphabetical
> characters only (i.e. without special characters).

Works for me.
--------------------------------------------------------------------
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]
--------------------------------------------------------------------

---

From: JINMEI Tatuya / 神明達哉<[email-masked]>
Date: Mon, 20 Dec 1999 16:25:05 +0900

>>>>> On Thu, 16 Dec 1999 09:51:26 -0800, 
>>>>> Brian Zill <[email-masked]> said:

> address, and IPv6 addresses are inherently big-endian.

Okay.

> readable either way.  I don't think this matters.

Okay, "readable" may be a subjective (and inappropriate) word.

> We'll just have to disagree on that one.

Okay. I don't mind changing our implementation on this point, but I'd
listen to others for a while. By the way, do you mind if we decide
this by majority? Or do you think this is essential (and you can't
compromise on this point in any way)?

> string that contains an address.  So I think ":", "@", and "-" are out.

(I'm not sure what conflict '-' has...DNS labels?, but) Okay, sounds
reasonable.

> the situations in which they need to quote it.

Is this really true and a merit? I can imagine that some applications
have the following code:

	if ((c = strchr(ipv6prefix, '/')) == NULL)
		return(error);
	prefixlen = atoi(c + 1);
	*c = '\0';
	prefixaddr = ipv6prefix;
	...

The execution of the code would fail when we give "4/fec0::/64" as the
variable "ipv6prefix". Of course we could change such applications to
accommodate them to the new syntax, but I'd personally prefer to avoid
such overhead as much as possible. What do you think?

>> 3. What is the appropriate syntax for zone IDs?
>> 

> Works for me.

Okay, thanks,

					JINMEI, Tatuya
					Communication Platform Lab.
					Corporate R&D Center, Toshiba Corp.
					[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]
--------------------------------------------------------------------