RE: Next question...

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

Tony Li wrote:
> Ok, so if the point is where to put locator selection policy, 
> I think that this is a much more bounded problem.  The two 
> obvious proposals are to
> 
> 1) Put the locators in the host, so that it can control which locator
>    it wants to use.  This allows the application to change locators if
>    its service is unacceptable.
> 
> 2) Put the locators in the border router.  This frees the host of the
>    management burden, but makes it somewhat harder for a site to
>    provide site-wide policy.
> 
> Note that either of these two alternatives could be enhanced 
> by further communications.  Either the border can inform the 
> host of site policy, or the host can inform the border of its 
> local policy.  One could also do both, but this is starting 
> to look like a dromedary.
> 
> Does that about cover the high points?

Yes. 

I suspect most of the complaints about host based locator selection is
really an indirect fear of loss of control. If that is true, having the
routing system inform hosts of policy preferences would allow for that
control in the general case, but still allow individual hosts to
override it when necessary. This could be done through a local policy to
respect ordering the RA, or possibly an explicit option. 

It would be possible for the hosts to inform the routing system about
policy preferences, but the state maintenance to support N,000 policies
in current hardware would not scale. Also, how is the host supposed to
know which routers need to be informed of the policy, or if traffic
shifts during a connection, which new router needs to be updated? RSVP
tried to do exactly this, but the routing community refused to support
it over scaling concerns.

Tony