Re: Multi6 WG Last Call (2 of 3) draft-ietf-multi6-things-to-think-about-00.txt

Hi Pekka,

> 2.3.3 Can your solution be aggregated and implemented site-wide?

This is now in Section 4.1: does your solution change existing 
aggregation methods?

> 2.3.4 Does your solution impact existing traffic engineering methods
> 
> I think these are rather important, even thought the latter is focused on
> MPLS, when it should be focusing on BGP traffic engineering practices
> instead.

We had this in there and nobody could understand how a solution could 
impact traffic engineering methods, other than by changing the 
aggregation methods.  Thus Section 4.1.

> 
> 2.  On the wire behavior
> 
> 2.1  How will your solution solve the multihoming problem?
> 
>     That's why we're here.  Remember, a reference is fine.
> 
> ==> this seems almost like asking, in an email context, 'how does your 
> proposal solve the spam problem?'.  This question is not good, because I 
> don't think we have sufficiently clearly defined what "the multihoming 
> problem" really is (and some might even argue it's multiple different 
> problems), and its unlikely that the solutions can even solve the whole 
> problem.
> 
> This will cause folks to answer, "the solution provides connection
> survivability, solving the multihoming problem" .. BUT THAT'S NOT
> THE (WHOLE OF) MULTIHOMING PROBLEM!
> 
> It's difficult to say how this should be fixed.  One way might be trying to
> precisely define what 'the multihoming problem' refers to.  One way 
> would be
> rewording the question so that the responder should try to describe which
> multihoming problem(s) the responder thinks what the solution is solving,
> and which not.  Reference to a list of multihoming problems would also be
> OK, but I don't think there is a good document laying these out.

What I am looking for, and perhaps a clarification *is* in order, is a 
scoping of what problem they think they're trying to solve.  This 
document doesn't require you to solve every problem, but simply to 
explain how your solution to the problem you think you're solving will 
impact the world we live in now.

> 
> 
> 2.7  Can multihoming capabilities be negotiated end to end during a
>      connection?
> 
>     If the proposal introduces additional overhead, can the information
>     be somehow piggybacked on messages that are already used?  This would
>     be useful in order to keep connection setup constant.  Please also
>     indicate any drawbacks that might apply due to this piggybacking.
> 
> ==> I already proposed the following new section in March:
> 
> ===
> 2.X Can multihoming setup be delayed from session setup?
> 
> If the proposal induces overhead (added bytes in packets, or
> additional packets), is it possible to delay that overhead (or
> "multihoming set-up") to happen after the session has been
> established?

This is included above based on your earlier feedback.

> 
> That is, is it possible to specify that multihoming benefits would
> only be achieved for sessions which last over XX seconds, to optimize
> away the cost of set-up for short-lived sessions?

And this may be too specific to a mechanism you have in mind.  For 
instance, perhaps this would be handled by an IP end host option.

> ===
> 
> Whether that should be a section of its own, or a couple of questions 
> merged
> e.g., in 2.7 is your call.
> 
> 3.4  How is the binding updated?
> 
>     Will transport connections remain up when new paths become available
>     or when old ones become unavailable?  How does the end node discover
>     these events?
> 
> ==> You should probably also ask:
> 
>     How long does it take to notice new paths?  How long does it take to
>     notice paths which are already used which have become unavailable?

That's a good question.
> 
> ...
> 
> 3.12  Are there any implications for scoped addressing?
> 
>     Please see RFC 3513 [1].  How does your mechanism interact with
>     multicast?
> 
> ==> what does 'multicast' have to do under 'scoped addressing'.  Granted,
> multicast addresses have a concept of scope, but maybe this calls for an
> additional question, 'Are there any implications for multicast', where
> multicast would include both global and non-globally scoped mcast.

The question is right there.  I attempted to borrow from IPv6 
nomenclature.  If you believe that nomenclature is failing us here, then 
we should change it, but we should do so elsewhere as well.

> 
> 4.3  Are there any changes to ICMP error semantics?
> 
>     Do you create new codes?  If so, why and what do they mean? Will a
>     host that is not aware of your scheme see them?
> 
> ==> add 'What would happen if such ICMP messages would end up being 
> filtered
> e.g. in a firewall?'..

Ok.

> 
> 5.  Name service interactions
> 
> ==> you discuss DNS in this section, but AFAICS, these issues could be
> generic if some other mapping function than DNS would be used.  Maybe this
> issue could be handled by adding something like:
> 
>   This section assumes that DNS might be used for a mapping function.  If
>   you are using some other method (see Section 3.8), please consider
>   separately both the impact on DNS, and the impact on your mapping 
> function
>   as appropriate.

I don't want to make quite so broad an assumption about the solution 
space, since we don't quite know which problem people are working on.

> 
> 
> editorial
> ---------

Will modify as appropriate.

Eliot