Erik Nordmark wrote:
> > It should be possible for a mobile node to use a site-local 
> prefix as 
> > long as it only ever roams within the site.  This seems to go along 
> > with the proposal that site-local prefixes should only be used in 
> > domains that are disconnected from the Internet.  If a 
> mobile node has 
> > a global home address, it should use that global address 
> all the time, 
> > I reckon.  Otherwise, if it only has a site-local address, then by 
> > definition it is only addressable at that site.  Users of such 
> > equipment should be made aware of that limitation.
> 
> Agreed when either site-locals or global addresses are used 
> in the site.
> 
> But unless site-locals are restricted there is a case when 
> both global and site-locals are used at the same time and 
> then presumably it would be possible to configure a mobile 
> node with both a global and site-local address. In that case 
> it is less clear what makes sense I think.

In terms of packet format, and registration with the HA, I see no reason
for SL to create any confusion. It is just one of the addresses that
could map to the current care-of address. The point the might be
confusing is the ability of the mobile node to detect that it is no
longer in the site. This should not be particularly difficult in the
case where the RA no longer contains a SL or global prefix for the HA,
because this is a good indication that the node is 'no longer in
Kansas'. The problem case is where the RA contains only SL. Is this the
home site where the global prefix went away or not? Since there is no
global prefix for the care-of, it would be hard to establish a mip-v6
ha/coa mapping. This does not mean SL fails in the case of the mobile
node, only that nodes that move between SL-enabled networks might need
to look for other hints to decide when they are no longer 'home'. 

Tony





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