Subject: Implementing the architectural principles of Scope-IDs

From: Jim Bound <[email-masked]>
Date: Sun, 14 Nov 1999 23:27:55 -0500

Brian,

Subject was: Re: draft-ietf-ipngwg-scopedaddr-format-00.txt

I changed the subject to another thread that I believe must run
simultaneously while we resolve the API issues and what our course will
be regarding scope-ids and I think other issues.

Right now the use of scope-ids (zone-id, or region-ids) is at best a
concept and principal within the addressing architecture for IPv6.

Before we all go off and change things I would like to hear some real
implementation ideas presented to see how scope-ids will work in
practice within IPv6.

It is my bias right now that they will not work without affecting other
systems within the IP protocol suite if they are to be implemented in
addition to them being architected.

Here is one way I thought of them being implemented:

1.  When an ip-name is looked-up to DNS and a response comes back the 
scope-id is attached to the api caller based on the scope-id the
interface is within.  So if a dns query goes out over le0 and le0 is
within scope-id of FUZZY then the address that comes back would be
assigned sin6-scope-id of FUZZY.

2.  Likewise when the name for an ip-address is looked up the scope-id
if going over le0 would be given FUZZY.

But what if the DNS server is the server for all scope-ids for this node
but the only interface to the DNS server happens to be within the
scope-id FUZZY.  And there is another scope-id called CLEAR on another
set of interfaces for the node.

For example the DNS at sin-scope-id FUZZY :

www.one.com  A6 fec0::234 (node is within FUZZY scope-id)

www.two.com  A6 fec0::234 (node is within CLEAR scope-id)

If the node sends out a DNS request for www.two.com on FUZZY scope-id
region/zone it will get back an address and assign it the sin6_scope_id
of FUZZY.  But the packet will in fact go to www.once.com not
www.two.com.

So my search for an implementation absract for sin6-scope-id will not
work with the assignment of the scope-id based on the interface on which
the query/response takes place for DNS, in the above example.

I think we need to nail down the use of this architecture precept of
scoped addresses except for link-local and multicast in the present Ipv6
aggr and addr specs (rfc 2373/2374).   In fact I am glad now they are
not at Draft Std as this gives me pause thinking about this.  We don't
have to revisit the entire notion of scope-ids for the purposes of getxx
APIs but we do need to prove it can work abstractly, and certainly
before we adopt any changes to the existing and deployed APIs.

Robert Elz's suggestion is looking pretty good to me right now!!!!

And if we can figure this out a strong "health warning" needs to be
attached to the solutions that there is even much pain with IPv6 when
you don't use Global Addresses.

/jim

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