Should we address conflicting addresses on single MT interface?

[Jeff Parker <jparker at axiowave.com>]

Alex -
	quoting from 
http://www.ietf.org/proceedings/03jul/I-D/draft-ietf-isis-wg-multi-topology-
06.txt

>> 12.2.2. Multiple MTs share an interface with overlapping addresses

    Some additional mechanism is needed to select the correct RIBs
    for the incoming IP packets to determine the correct RIB to make
    a forwarding decision. For example, if the topologies are
    QoS partitioned, then the DSCP bits in the IP packet header can
    be utilized to make the decision. Some IP header or even packet
    data information may be checked to make the forwarding table
    selection, such as source IP address in the header can be used
    to determine the desired forwarding behavior.

>>     The generic approach of packet to multiple MT RIB mapping over
>>     the same inbound interface is outside the scope of this draft.

I assume that the motivation to sort this out would be to provide 
interoperable implementations.  The draft defines a mechanism, and 
leaves open the definition of particulars in this case.  

Is this something that needs to be decided now?  Are
there competing interpretations?  Are there competing
demands for this functionality?  I see the value in
having agreement, but wonder if we have enough experience
with the idea to know how ISPs would want to use it tomorrow.   

- jeff parker