RE: survivability, rewriting

[Erik Nordmark <Erik.Nordmark@sun.com>]

> > 1. The ULPs need to know the addresses of the node itself to be able
> >    to perform certain forms of referal. But that doesn't prevent
> >    the node to issue IP packets with a source locator that doesn't
> >    include the upper bits of the address *as long as* the host knows
> >    that there is a rewriting router along the path.
> >
> I am sorry, Erik, but i don't understand this argument.
> Those rewritable addresses wouldn't be passed for referrals purposes, they
> are just an artifact to let the M6 layer to notify the border router that
> they should complete with a real prefix. The application would only be aware
> of the AID. The referals would contain real locators. I guess i am missing
> your point here :-(

I guess I wasn't very clear - there are two separate issues mixed together.

One could allocate a prefix, such a 0::/48 if you ignore that
there is some other use for that, for use as the source locator.
Thus the host could send packets with that source *IF* it knows that there
is a rewriting router in the path which will insert the correct
high-order bits in the source locator.
But this is tricky to migrate to since the host would need to be able
to tell whether its site has such rewriting routers at the boundary;
if the 0::/48 makes it to a remote peer it will not be able to respond.
How can it do this?
Having the source send packets with the actual source locator prefix
plus indicating that it is ok to rewrite it doesn't have this issue;
if there is no rewriting router in the path the source locator
stays unmodified but it still usable for the peer to respond.

Second part is just the observation that having the node send packets with
a fixed source prefix (such as 0::/48) doesn't remove the need for
the ULP/apps to know the actual source locator, since it might need
this as part of referals.

   Erik