Subject: sockaddr_in6::sin6_scope_id use

From: "Edward Boden" <[email-masked]>
Date: Sun, 21 Apr 2002 18:51:49 -0400

What should the sockaddr_in6::sin6_scope_id field contain?  An interface
index or a {scope, zone} indicator?   It would be better (simpler, more
flexible, easier to understand, etc.) if we could use it for either.  (For
example, in light of the defined if_nametoindex(), if_indextoname() and
related functions.)

The current basic socket enhancements draft
(draft-ietf-ipngwg-2553bis-05.txt) specifies that this 32-bit integer
"identifies a set of interfaces".  More specifically, a "interface index"
for a link-local scope sin6_addr, or a "site identifier" for a site-local
sin6_addr. (section 3.3)  (More thoughts follow, in the draft, with no
mention of zones or zoneid.)

The current ip6 scoped addr architecture draft
(draft-ietf-ipngwg-scoping-arch-03.txt) suggests a 32-bit representation of
{scope,zone} by using the upper-most 4 bits for the scope, and the rest of
the value used to specify the zone (section 12.2).

Proposal: allow sin6_scope_id to be used for either interface index or a
{scope, zone} indicator.  This can be simply accomplished by adopting the
scoped address architecture representation for {scope, zone}.   And, allow
the interpretation of 0x0 in the 'scope' portion of sin6_scope_id to mean
the rest of the value is an interface index.

(There are other ways, of course.)

Do people agree with the idea of using sin6_scope_id for either?

Ed Boden

--------------------------------------------------------------------
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: Markku Savela <[email-masked]>
Date: Mon, 22 Apr 2002 02:07:01 +0300

> for a link-local scope sin6_addr,

I think it should say "link-local scope id" for link local address, to
be logical (which is not necessarily same as interface index).

The idea of having a scope id which is of different type than than the
address was rejected. (Which makes me wonder why does the scoped
architecture draft talk about having the 4 bits in ID assigned to
scope type: I think this is internal implementation issue, and not
required, if system works without such trick).

However, I still don't have strong opininion about this, e.g. whether
scope identifiers type can differ from type of address.

Currently, I'm writing a version where identifiers scope type is
*always* determined from the address -- you cannot have isolated scope
id. Seems to give fairly clean result.. so far...

---

From: Francis Dupont <[email-masked]>
Date: Tue, 23 Apr 2002 11:54:05 +0200

In your previous mail you wrote:

   address was rejected.

=> please don't reopen old discussion if you have no new argument.

   Currently, I'm writing a version where identifiers scope type is
   *always* determined from the address -- you cannot have isolated scope id.

=> the consensus is we'd like to have "isolated" scope ids.

Regards

[email-masked]

---

From: Markku Savela <[email-masked]>
Date: Tue, 23 Apr 2002 14:15:15 +0300

> From: Francis Dupont <[email-masked]>
> 

I'm Sorry. I have then missed the discussion on this mailing list
since Seattle meeting, after which in followup messages I was
mistakenly left impression that 4+28 model was not chosen.

In any case, it was my intention to open this discussion, I just
forgot the "?"-mark after the above statement!

> => the consensus is we'd like to have "isolated" scope ids.

This is fine, I'm not objecting to 4+28. I was just noting that so far
while implementing scoped addressing architecture, I have not found
any need for 4+28 yet.
--------------------------------------------------------------------
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: Markku Savela <[email-masked]>
Date: Tue, 23 Apr 2002 14:41:49 +0300

Sigh... typing errors plague me...

> From: Markku Savela <[email-masked]>

> forgot the "?"-mark after the above statement!

Should have written..

 In any case, it was NOT my intention to open this discussion, ...