RE: The state of IPv6 multihoming development

["Tony Hain" <alh-ietf@tndh.net>]

Christian Kuhtz wrote:
> > A host decision does not affect traffic shaping for the outbound 
> > direction. The only choice it is making in that space is 
> the dst addr, 
> > and it has that responsibility today, even though it has no 
> > deterministic means of making that choice. The IPv6 address 
> selection 
> > rules add structure to that process.
> 
> maybe i got this all wrong, but...
> 
> if this means that a host is expected to make a decision 
> which path to 
> chose, i'm sorry, i don't see that happening and consider it 
> an absurd 
> notion.

You did miss my point which was that the routers will always decide the
path. The only thing the host decides is which entry in a dns response
it will use for the dst, and which of its addresses it will use. 

> 
> the last thing i want is for an oracle server, or webserver, 
> or whatever to make a routing decision as to which addr or 
> iface to use.  seems the trend is exactly the opposite.. to 
> get that decision _away_ from the host and have the backbone 
> of a given org take care of traffic management.
> 
> any type of te will have to aggregated at a higher level than hosts. 

Yes, and the reality is that this will happen no matter what the host
decides to use for addresses. This whole discussion is a bogon caused by
the fear that the host might make any kind of decision. REALITY CHECK:
it already does sort through the list of addresses in a DNS response,
and if it has multiple interfaces it already has to decide which of
those to use. Once the packet is in flight, the routers decide the path
because that is their job.

>  
> some of this is a technology and architectural decision, some 
> of this is also real world organizational skills.  i do not 
> want to create a rqmt 
> that says that systems operations folks have to be omnipotent 
> systems & network wizards to configuration, manage and 
> troubleshoot their hosts.
> 
> and i think that's exactly what you do when you push te 
> capabilities down to the host level.

Nobody is pushing TE to the host level, there is simply a fear that will
happen when a host chooses which of its addresses it will use as a
source.

> 
> > For the inbound direction, the remote and intermediate network 
> > managers have more impact on the actual path the bits will 
> take than 
> > the origin choice of source addr. All we have today is the illusion 
> > that a network manager can direct traffic toward his 
> network. Having 1 
> > or N addresses doesn't change the granularity of traffic 
> engineering, 
> > so the argument is bogus. What it really boils down to is 
> that nodes 
> > outside the network manager's direct control are making a decision 
> > (any decision). This is about trust, not traffic engineering.
> 
> nevermind that there are various bgp knobs today which allow 
> you to do exactly that (regulate inbound traffic) by changing 
> what prefixes are advertised where and how.  

Over a diminishing scope of influence. Yes you affect immediate
neighbors, and depending on their filtering policy, you may influence
their direct peers, but the strength of your ability to manage inbound
traffic diminishes at every policy boundary. 

Tony

> there is a 
> gating factor here in today's ipv4 world in terms of the 
> smallest chunk of addresses which can be pulled out of a 
> given aggregate.
> 
> thanks,
> christian
>