[DNA] Issue about multiply connected to the same link and DNA beingper-interface or not (was Re: WG LC comments on draft-ietf-dna-goals-01.txt)

[Pekka Nikander <pekka.nikander@nomadiclab.com>]

>>> I see few reason to add "or multiple times to the same link". I think
>>> that's a different case and we may obscure the main issue, 'multiple
>>> attachment', if we add that.
>>
>> Well, I was thinking about the situation where the host is
>> connected through several interfaces to the same link.
>> In some way, this is a special case of a host being connected
>> through several interfaces to several different links.
>>
>> I am not sure how to formulate that properly, but IMHO the whole
>> continuum should be covered by G10.  I don't see it covered
>> by the other goals.
>
> DNA scheme is run per-interface because some IP configuration,
> such as IPv6 address, is interface specific.

Well, I do see there some potentiality for using DNA related
information across different interfaces.  Hence, I would _not_
like to mandate DNA to be per-interface.

For example, if a host has earlier been connected twice to the
same link through two different interfaces, and then it detects
that one of the interfaces has undergone a link change, IMHO that
is a strong indication that there may have been a link change
at the other interface, too.

<snip>

> However, when multiple interfaces of a host are connected to the
> same link, it will result in few problem. Each interface may run DNA
> scheme to check for link change and update its IP configuration in
> case of a link change.

I agree that there shouldn't be that many new *problems* related
to DNA.  However, I think it may be possible to use some DNA
related information for *optimising* behaviour.  We have to
remember that DNA is mostly about optimisation, anyway.

> I think the expression 'multiple interfaces' in G10 is confusing.
> I propose to change G 10 as
>
>    G10 Hosts in particular wireless environments may perceive routers
>       reachable on different links.  DNA schemes should take into
>       consideration the case where a host is attached to more than one
>       link at the same time.

This is better.

> Also, as Alper pointed, we'd better explicitly mention that DNA is
> run per-interface. I added the following in Introduction.
>
>    ..........................of its IP configuration, is called 
> Detecting Network
>    Attachment (DNA).
>
>    DNA scheme is run per interface because some IP configuration, such
>    as IPv6 address, is interface specific.  When a host has multiple
>    interfaces, each interface separately check for link change to 
> verify
>    each one's IP configuration.

As I wrote above, I don't agree with this.  I think this is unnecessary
in the goals document.  I don't think we should include it.
OTOH, if other's in the WG think otherwise, I won't insist.

--Pekka