RE: (multi6) control / load balancing of ingress traffic.

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

Michel Py wrote:
> Not necessarily, see below. Or maybe, this might be true as of today
> but the multihoming solution we want for IPv6 is not what we have
> today for v4.

I get the impression from comments on the list that there are different
opinions on what the goal is. Some people want exactly what they have
today, some people want a network / centrally managed approach, some
people want a host / distributed approach, and others want a mix of the
above. The current requirements draft tries to give each group what they
want, even though the totally network centric and the totally host
centric approaches are mutually exclusive. Until we have agreement on
what we want for an IPv6 solution, no progress will be made.


> - If that multihoming protocol bases its decisions on info provided by
> the
> destination, you can truly says that the destination controls its own
> ingress traffic. DESTINATION ADDRESS SELECTION is the key here, not
> routing.

Are you proposing to tie the DNS response to a system which keeps track
of probable paths from the current requestor and current load
distribution policy so the source can only pick the destination address
you want??? In any case routing is part of the key, and destination
address only plays a role for those parts of the infrastructure that
route on that rather than a default. If a source site defaults to a
particular ISP which the destination is also connected to, there is
nothing in the destination address selection that will change the way
traffic flows.


> Like it or not, part of the multihoming solution is a multiple PA
> address
> without a PI that this company in Redmond, WA and some other
> people are
> working on.

I happen to be one of the people that believes that host address
selection is part of the answer to the long term problem. That does not
mean that a destination site can micro-manage its incoming load
balancing though, unless there is a connection to the DNS response which
limits the sources choices to current load balancing policy and the
concept of a default route is completely removed from the system.


> Bottom line is: multiple-address solutions do not give a hoot to
> routing.

Yes they do, they are just a mechanism to try and 'best-guess' what the
routing system will be doing. While it is possible for policy to say
select from any available address, most implementations will default to
longest matching between available source and available destination
addresses, because that approach is most likely to take the shortest
path through the infrastructure. In any case once the packet leaves the
host it is the routing system that determines the packet path, not
address selection.


Maybe the problem is the assumption that a single approach can be found
for very different functional requirements. If a site multi-homes for
resiliency, host based address selection approaches are appropriate,
while if a site multi-homes with the intent of micro-managed load
balancing, those are inappropriate and route injection mechanisms make
more sense (but I still maintain that a destination has limited control
over the absolute path).

Tony