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

Erik

>> 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.
>
> do you have a concrete example where this makes sense?

The specific example, though simplistic, that I've had in my mind
is my home setting with my laptop.  I have a bridged Ethernet and
WLAN.  When my laptop notices that I've disconnected it from the
Ethernet, I may have just moving it around in our house, and it
is still connected to the same link through WLAN.  On the other
hand, I may have suspended it and moved it e.g. to the office,
in which case it is now attached to a different WLAN.

Another example that I could imagine is a large operator network
that from an IPv6 point of view acts as a single, large "LAN"
or NBMA link.  (I know one operator that has plans like that.)
The operator might offer different radio access technologies to
access that "large LAN".  When one radio interface undergoes a
change, it may make sense to quickly verify whether the other
interfaces still are connected to the "large LAN".

In general, if two interfaces are connected to the same subnet,
and one of the undergoes a link change, it often makes sense to
check if the other one has also went through a link change.

> I don't have a problem relaxing the wording in the goals draft
> to not accidentically preclude optimizations which share
> information between interfaces, but I don't understand your
> example above.

I was mostly objecting the notion that we should keep DNA on
separate interfaces _completely_ independent.  To me, it looks
like that there are cases when they are not.  I am oblivious
how to handle this, through link hints, relaxing the language
in the goals draft, or whatever.

--Pekka