RE: The state of IPv6 multihoming development

["Tony Li" <Tony.Li@procket.com>]

|   If the multihoming processing is done outside the host, 
|   then packets all
|   packets must be presented to the host with the identifiers 
|   as the source
|   and destinations addresses. If this is done inside the host 
|   then this
|   isn't strictly required, but it is likely the transport 
|   layer will want
|   to see just the identifiers so the IP layer will have to 
|   reconstitute
|   those.


Fair enough, but if we go down the GSE direction, the packet has
the identifier in it already when it arrives at the host and the
identifier is never modified in flight.  In my book, that gives us 
the desired end-to-end connectivity.


|   > The host should select the identifier, both for itself and for the
|   > destination.  The border router selects the locators for both the
|   > source and the destination.  This allows the border 
|   router to implement
|   > policy in a reasonable way.
|   
|   Agree. However, do we want to involve a border router in the locator
|   discovery process?


If you want to address Craig's concern about being able to affect locator
policy for the entire enterprise in a scalable way, you kinda have to.  

   
|   The basic idea is simple: the IP addresses the transport layer uses
|   become the identifiers of a session. In transit, these identifiers
|   may/must be replaced by locators, but they identifiers are restored
|   before the packet reaches the transport layer at the other end.


Yes, but if you do wholesale identifier replacement, then you get into
trouble with protocols carrying identifiers around above the network layer.

A nice way of fixing this is to establish the principle that locators
are never carried around above the network layer, only the identifier.

   
|   Discovery is hard to do, but if we can solve the associated 
|   problems it
|   provides a much stronger mechanism because then a host can have a
|   single, portable identifier. It would be good if we could provide an
|   upgrade path from negotiation to discovery.


I have to agree. I prefer discovery as well.

Tony