Re: [netmod] [Lsr] I-D Action: draft-ietf-lsr-ospfv3-extended-lsa-yang-10.txt

[Andy Bierman <[e-mail]>]

On Thu, Apr 14, 2022 at 12:38 PM Jürgen Schönwälder <
[e-mail]> wrote:

> On Thu, Apr 14, 2022 at 09:23:38AM -0700, Andy Bierman wrote:
> > >
> > So is this a correct summary:
> >
> >  - zone index is not used in IPv4 at all
>
> There are link-local IPv4 addresses, they are less wide-spread since
> IPv4 stacks generally do not auto-configure IPv4 link-local addresses.
> Nobody will be able to confirm "not used at all", this questions is
> somewhat rhetoric since nobody can answer it.
>
> >  - zone index is not configured by a client in IPv6 at all
>
> Configuring zone indexes is required in many cases to reach services
> that are only reachable via link-local addresses. I mentioned the DNS
> resolver example and this applies to pretty much any transport layer
> endpoint. This is why by design (and not by accident) the with zone
> version of ip-address is used in the inet:host typedef.
>
> >  - zone index is assigned by the system (as needed) to IPv6 link-local
> > addresses
>
> A link-local address exists on a link and as such does not need a zone
> index as long it is used on the link. However, when you want to refer
> to a link-local address on a system with more than one link, then the
> link-local address is ambiguous and to disambiguate things you either
> specify in adding the interface to be used or you embed the zone index
> in the address. Since application code usually assumes that a
> transport address is an (ip-address, port) tuple, people converged on
> adding the zone to the ip address (instead of rewriting all APIs to
> use (ip-address, port, interface) tuples. The zoned IP address
> notation is meanwhile widely supported. This is why we have, for
> example, RFC 6874 (but the IPv6 folks have a reoccuring debate about
> the question whether the % needs to be percent encoded or not,
> draft-carpenter-6man-rfc6874bis-03).
>
> > I want to add a server option in our code to always reject (or alter)
> > an edit that contains a zone index.  I need to know the consensus on
> > whether it is OK to ignore a zone index from a client.
>
> It is your choice to design a product that will not work with
> link-local addresses. For IETF data models, I expect that the bar is
> higher and that people can expect that IETF data models are written to
> also work with link-local addresses. If implementers than decide that
> their users do not need to work with link-local addresses, so be it,
> you can make your server reject the optional zone index. But others
> can decide that they customers can also work with link-local
> addresses. If we blindly remove the zone index from ip-address, then
> the IETF would break data models for those who consider link-local
> addresses a first class citizen.
>
>
A server option is useful for an implementation that does not
support zone index configuration. It is an implementation detail so out of
scope.

The proposal is for a 2 year phase to change modules
that really do want a zone index.  It is not blindly removing the zone
index.


> Nothing in RFC 6241 suggests that this is OK for <edit-config>.
>
> I have no clue what you mean. If your server recceives a value that
> your server does not support, you reject the value.
>
> /js
>

Andy



>
> PS: I recall the side meetings with IPv6 people to sort out how we add
>     proper IPv6 support to MIB modules, which led to RFC 4001, which
>     later influenced the YANG typedefs. Almost 20 years later (and
>     IPv6 deployed at a much larger scale) I find myself in a
>     discussion where people question that we need to support
>     link-local addresses. This is very irritating.
>
>     Apparently, getaddrinfo() implementations tend to handle zoned
>     link-local addresses just fine and any code that passes a zoned ip
>     address string to getaddrinfo() will likely return you a socket
>     address with the sin6_scope_id filled in properly. You actually
>     have to do extra work to prevent the right thing to happen if your
>     code passes strings on to getaddinfo(). I am puzzled why people
>     want to do this.
>
> --
> Jürgen Schönwälder              Jacobs University Bremen gGmbH
> Phone: [phone]         Campus Ring 1 | 28759 Bremen | Germany
> Fax:   [phone]         <https://www.jacobs-university.de/>
>